AEROSOL GENERATOR ARTICLE WITH UPSTREAM SECTION, HOLLOW TUBULAR ELEMENT AND NOZZLE ELEMENT

Abstract

An aerosol generating article (10) is provided comprising an aerosol generating substrate bar (12) having a length of between approximately 8 mm and approximately 16 mm. The aerosol generating article comprises an upstream element (42). The upstream element is provided upstream of the aerosol generating substrate bar. The upstream element has an external diameter of between approximately 6 mm and approximately 8 mm. The aerosol generating article comprises a nozzle element (50). The nozzle element is provided downstream of the aerosol generating substrate bar. The aerosol generating article comprises a hollow tubular element (20). The hollow tubular element is provided between the aerosol generating substrate bar and the nozzle element. An internal volume defined by the hollow tubular element is at least approximately 300 cubic millimeters.A combined length of the hollow tubular element and the nozzle element is between approximately 24 mm and approximately 32 mm.

Description

AEROSOL GENERATOR ARTICLE WITH UPSTREAM SECTION, HOLLOW TUBULAR ELEMENT AND NOZZLE ELEMENT The present invention relates to an aerosol generating article comprising an aerosol generating substrate adapted to produce an inhalable aerosol upon heating. This description also relates to an aerosol generating system comprising an aerosol generating device and an aerosol generating article. Aerosol-generating articles in which an aerosol-generating substrate, such as a tobacco-containing substrate, is heated rather than burned are known in the art. Typically, in such heated smoking articles, an aerosol is generated by the transfer of heat from a heat source to a physically separate aerosol-generating material or substrate, which may be located in contact with, within, around, or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by the heat transfer from the heat source and are carried in the air drawn through the article. As the released compounds cool, they condense to form an aerosol. A number of prior art documents describe aerosol-generating devices for use with aerosol-generating articles. Such devices include, for example, electrically heated aerosol-generating devices in which an aerosol is generated by heat transfer from one or more electrical heating elements of the aerosol-generating device to the aerosol-generating substrate of a heated aerosol-generating article. For example, electrically heated aerosol-generating devices comprising an internal heating sheet adapted for insertion into the aerosol-generating substrate have been proposed. The use of an aerosol-generating article in combination with an external heating system is also known.For example, WO 2020 / 115151 describes the provision of one or more heating elements arranged around the periphery of the aerosol-generating article when the aerosol-generating article is received in a cavity of the aerosol-generating device. Alternatively, inductively heated aerosol-generating articles comprising an aerosol-generating substrate and a susceptor disposed within the aerosol-generating substrate have been proposed in WO 2015 / 176898. ocrmnn / cznz / R / vi Aerosol-generating articles, in which a tobacco-containing substrate is heated rather than burned, present a number of challenges not encountered with conventional smoking articles. First, the tobacco-containing substrates are typically heated to significantly lower temperatures compared to the temperatures reached by the combustion front in a conventional cigarette. This can impact the release of nicotine from the tobacco-containing substrate and the nicotine delivery to the consumer. At the same time, if the heating temperature is increased in an attempt to boost nicotine delivery, then the generated aerosol typically needs to be cooled more extensively and more rapidly before reaching the consumer.However, technical solutions commonly used to cool mainstream smoke in conventional smoking articles, such as providing a high-efficiency filtration segment at the mouth end of a cigarette, can have undesirable effects in aerosol-generating articles where a tobacco-containing substrate is heated rather than burned, as they can reduce nicotine delivery. Therefore, it would be desirable to provide new aerosol-generating articles that can consistently ensure satisfactory aerosol delivery to the consumer. Secondly, there is a general need for aerosol generating devices that are easy to use and offer improved practicality. For example, it would be convenient to provide an aerosol generating device that can be easily inserted into a heating cavity and that can also be securely held within the heating cavity so that it does not come loose during use. Therefore, it would be desirable to provide a new and improved aerosol-generating device adapted to achieve at least one of the desirable results described above. Furthermore, it would be desirable to provide such an aerosol-generating device that can be manufactured efficiently and at high speed, preferably with a satisfactory RTD and low RTD variability from one device to another. This description refers to an aerosol generating article. The aerosol generating article may comprise an aerosol generating substrate bar having a length of between approximately 8 mm and approximately 16 mm. The aerosol generating article may comprise an upstream section. The upstream section may comprise an upstream element. The upstream element may be provided upstream of the aerosol generating substrate bar. The upstream element may have an external diameter of between approximately 6 mm and approximately 8 mm. The aerosol generating article may comprise a nozzle element. The nozzle element may be provided downstream of the aerosol generating substrate bar. The aerosol generating article may comprise a hollow tubular element.The hollow tubular element may be provided between the aerosol-generating substrate bar and the nozzle element. The internal volume defined by the hollow tubular element may be at least approximately 300 cubic millimeters. The combined length of the hollow tubular element and the nozzle element may be between approximately 24 mm and approximately 32 mm. According to the present invention, an aerosol generating article is provided comprising an aerosol generating substrate bar having a length of between approximately 8 mm and approximately 16 mm. The aerosol generating article comprises an upstream element. The upstream element is provided upstream of the aerosol generating substrate bar. The upstream element has an outer diameter of between approximately 6 mm and approximately 8 mm. The aerosol generating article comprises a nozzle element. The nozzle element is provided downstream of the aerosol generating substrate bar. The aerosol generating article comprises a hollow tubular element. The hollow tubular element is provided between the aerosol generating substrate bar and the nozzle element. An internal volume defined by the hollow tubular element is at least approximately 300 cubic millimeters.A combined length of the hollow tubular element and the nozzle element is between approximately 24 mm and approximately 32 mm. Furthermore, in accordance with the present description, an aerosol generating system is provided comprising an aerosol generating article as set forth above and an aerosol generating device, wherein the aerosol generating device comprises a heating chamber for receiving the aerosol generating article and a heating member disposed in or around a periphery of the heating chamber. The aerosol-generating article according to the present invention provides an improved configuration that reduces the potential risk of accidental misalignment or dislodgement of an aerosol-generating article during its use in an aerosol-generating device. Extending the upstream or inserted portion of the article to minimize this risk of dislodgement is inconvenient because it requires more material, the device cavity would need to be excessively long, and insertion may become more complicated for a user. Providing a shorter downstream (or protruding) portion of the article is also an option to decrease this risk, but this may negatively impact ease of use because there would be less article for a user to grasp for removal.Additionally, there may be an adverse effect on the aerosol cooling benefits that arise from having a relatively long downstream portion. Increasing the outer diameter of the inserted portions of the item to ensure a tighter fit with a device cavity is one option, but such portions, particularly the aerosol-generating substrate bar, can be brittle under compression and may shrink when heated. During the heating of the aerosol-generating substrate bar, the substrate may gradually shrink, which can be detrimental to the item's fit within the device. Providing a non-tobacco component upstream of the substrate improves the item's fit or anchoring within the device because the upstream element will be able to engage with the device cavity, whereas the tobacco portion may partially and progressively lose its fit during use as it shrinks. In the event of any partial slippage or displacement of the aerosol-generating item from the device cavity, a defined length of the aerosol-generating element bar can ensure consistent alignment of the heater with at least part of the aerosol-generating substrate. Providing a defined upstream element that is relatively long and wide, a defined length for the aerosol-generating substrate bar, and a defined combined length for the downstream components ensures consistent engagement of the article throughout its use within an aerosol-generating device, thereby minimizing the risk of accidental dislodgement or misalignment. The present invention achieves a balance between the amount of article available for insertion into the device cavity and the amount available for protrusion. During heating of the aerosol-generating substrate bar, the substrate gradually contracts, which can be detrimental to the article's fit within the device.Providing relatively long, non-tobacco components immediately downstream and upstream of the substrate improves the coupling of the item within the device cavity because the dimensions of the upstream item and an inserted longitudinal portion of the downstream components will be able to couple with the device cavity, whereas the tobacco portion may partially lose coupling during use. ocnt?nn / C7n7 / e / Yi A relatively long downstream section formed by the hollow tubular element and the nozzle element also contributes to increasing the amount of inserted portion of the item, thus decreasing the risk of accidental drop, while also providing a relatively long portion of the item protruding from the device, which will facilitate its removal and placement. In the event of any partial slippage or displacement of the aerosol-generating item from the device cavity, a defined length of the aerosol-generating substrate bar can ensure some overlap of an external heater with at least part of the aerosol-generating substrate. Additionally, in an aerosol generating article according to the present invention, the length of the aerosol generating substrate rod, the volume of the internal cavity of the hollow tubular element of the article has been selected to provide rapid cooling of the species flowing along the cavity defined internally by the hollow tubular element. Therefore, the selected diameter of the upstream element, the internal volume of the hollow tubular element, and the combined length of the hollow tubular element and the nozzle element in the articles according to the present invention provide a combination that optimizes the placement of the substrate within the aerosol generating device and reduces the risk of unintentional release of the article from an aerosol generating device. As mentioned above, an aerosol-generating article according to the present invention comprises an aerosol-generating substrate bar. Furthermore, an aerosol-generating article according to the present invention comprises one or more elements provided downstream of the aerosol-generating substrate bar. The one or more elements downstream of the aerosol-generating substrate bar form a downstream section of the aerosol-generating article. Additionally, an aerosol-generating article according to the present invention may comprise an element provided upstream of the aerosol-generating substrate bar. The element upstream of the aerosol-generating substrate bar defines an upstream section of the aerosol-generating article. As defined above, the aerosol-generating article according to the present invention comprises an aerosol-generating substrate rod. The aerosol-generating substrate rod is preferably enclosed by a wrapper, such as a cap wrapper. The aerosol-generating substrate bar preferably has a length of at least approximately 8 millimeters. Preferably, the aerosol-generating substrate bar has a length of at least approximately 9 millimeters. More preferably, the aerosol-generating substrate bar has a length of at least approximately 10 millimeters. For example, the aerosol-generating substrate rod preferably has a length of between approximately 8 millimeters and approximately 16 millimeters, or between approximately 9 millimeters and approximately 15 millimeters, or between approximately 10 millimeters and approximately 14 millimeters. In a particularly preferred embodiment, the aerosol-generating substrate rod has a length of approximately 12 millimeters. Preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is at least approximately 0.15, with higher preference at least approximately 0.2, with maximum preference at least approximately 0.22. Preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is less than or equal to 0.35, more preferably less than or equal to approximately 0.33, more preferably less than or equal to approximately 0.3. In particularly preferred embodiments of the present invention, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is approximately 0.25. By adjusting the length of the aerosol-generating substrate rod within any of the ranges described above, and by controlling the density of the aerosol-generating substrate itself, the inventors have found it easier to better and more consistently control the overall RTD of the aerosol-generating article. Furthermore, since the rod length is also predefined, it is easier to ensure convenient placement of a ventilation zone relative to the substrate and the heating device during use. The aerosol-generating substrate bar preferably has an outer diameter that is approximately equal to the outer diameter of the aerosol-generating article. The “outer diameter of the aerosol generating substrate bar” can be calculated as the average of a plurality of aerosol generating substrate bar diameter measurements taken at different locations along the length of the aerosol generating substrate bar. Preferably, the aerosol-generating substrate bar has an outer diameter of at least approximately 5 millimeters. More preferably, the aerosol-generating substrate bar has an outer diameter of at least approximately 6 millimeters. Even more preferably, the aerosol-generating substrate bar has an outer diameter of at least approximately 7 millimeters. The aerosol-generating substrate bar preferably has an outer diameter less than or equal to approximately 12 millimeters. More preferably, the aerosol-generating substrate bar has an outer diameter less than or equal to approximately 10 millimeters. Even more preferably, the aerosol-generating substrate bar has an outer diameter less than or equal to approximately 8 millimeters. In general, it has been observed that the smaller the diameter of the aerosol-generating substrate bar, the lower the temperature required to raise its core temperature sufficiently to release enough vaporizable species from the substrate to form the desired amount of aerosol. At the same time, and without wishing to be limited by theory, it is understood that a smaller diameter of the aerosol-generating substrate bar allows for faster penetration of the heat supplied to the aerosol-generating article throughout the entire volume of the aerosol-forming substrate. However, when the diameter of the aerosol-generating substrate bar is too small, the volume-to-surface-area ratio of the aerosol-generating substrate becomes less favorable, as the amount of available aerosol-forming substrate decreases. A diameter of the aerosol-generating substrate bar that falls within the ranges described herein is particularly advantageous in terms of balancing energy consumption and aerosol output. This advantage is especially noticeable when an aerosol-generating article comprising a substrate bar of the diameter described herein is used in conjunction with an external heater arranged around the periphery of the article. Under such operating conditions, it has been observed that less thermal energy is required to achieve a sufficiently high temperature in the core of the substrate bar and, more generally, in the core of the article.Therefore, when operating at lower temperatures, a desired target temperature at the core of the aerosol generating substrate can be achieved within a conveniently reduced timeframe and with lower energy consumption. In some embodiments, the aerosol-generating substrate bar has an outer diameter of approximately 5 mm to approximately 12 mm, preferably from approximately 6 mm to approximately 12 mm, with a greater preference of approximately 7 mm to approximately 12 mm. In other embodiments, the aerosol-generating substrate bar has an outer diameter of approximately 5 mm to approximately 12 mm, preferably from approximately 6 mm to approximately 10 mm, with a greater preference of approximately 7 mm to approximately 10 mm. In further embodiments, the aerosol-generating substrate bar has an outer diameter of approximately 5 mm to approximately 8 mm, preferably from approximately 6 mm to approximately 8 mm, with a greater preference of approximately 7 mm to approximately 8 mm. In a particularly preferred embodiment, the aerosol-generating substrate bar has an outer diameter of less than approximately 7.5 millimeters. For example, the aerosol-generating substrate bar may have an outer diameter of approximately 7.2 millimeters. The ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article may be at least approximately 0.10. Preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is at least approximately 0.15. More preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is at least approximately 0.20. Even more preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is at least approximately 0.25. In general, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article may be less than or equal to approximately 0.60. Preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is less than or equal to approximately 0.50. More preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is less than or equal to approximately 0.45. Even more preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is less than or equal to approximately 0.40. In particularly preferred embodiments, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is less than or equal to approximately 0.35, and with the highest preference less than or equal to approximately 0.30. ocnt?nn / C7n7 / e / Yi In some embodiments, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is approximately 0.10 to approximately 0.45, preferably approximately 0.15 to approximately 0.45, more preferably approximately 0.20 to approximately 0.45, and even more preferably approximately 0.25 to approximately 0.45. In other embodiments, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is approximately 0.10 to approximately 0.40, preferably approximately 0.15 to approximately 0.40, more preferably approximately 0.20 to approximately 0.40, and even more preferably approximately 0.25 to approximately 0.40.In additional embodiments, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is approximately 0.10 to approximately 0.35, preferably approximately 0.15 to approximately 0.35, more preferably approximately 0.20 to approximately 0.35, and even more preferably approximately 0.25 to approximately 0.35. In additional embodiments, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is approximately 0.10 to approximately 0.30, preferably approximately 0.15 to approximately 0.30, more preferably approximately 0.20 to approximately 0.30, and even more preferably approximately 0.25 to approximately 0.30. Preferably, the aerosol-generating substrate bar has an essentially uniform cross-section along its length. More specifically, the aerosol-generating substrate bath has an essentially circular cross-section. In an aerosol-generating article according to the present invention, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article may be less than or equal to approximately 0.60. Preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article may be less than or equal to approximately 0.50. More preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article may be less than or equal to approximately 0.40. Even more preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article may be less than or equal to approximately 0.30. In an aerosol-generating article according to the present invention, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article may be at least approximately 0.10. Preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article may be at least approximately 0.15. More preferably, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article may be at least approximately 0.20. In particularly preferred embodiments, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article may be at least approximately 0.25. In some embodiments, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is approximately 0.10 to approximately 0.60, preferably approximately 0.15 to approximately 0.60, more preferably approximately 0.20 to approximately 0.60, and even more preferably approximately 0.25 to approximately 0.60. In other embodiments, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is approximately 0.10 to approximately 0.50, preferably approximately 0.15 to approximately 0.50, more preferably approximately 0.20 to approximately 0.50, and even more preferably approximately 0.25 to approximately 0.50.In additional embodiments, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article is approximately 0.10 to approximately 0.40, preferably approximately 0.15 to approximately 0.40, more preferably approximately 0.20 to approximately 0.40, and even more preferably approximately 0.25 to approximately 0.40. By way of example, the ratio of the length of the aerosol-generating substrate bar to the total length of the aerosol-generating article may be approximately 0.25 to approximately 0.30, preferably approximately 0.27. Preferably, the density of the aerosol-generating substrate is at least approximately 150 mg per cubic centimeter. More preferably, the density of the aerosol-generating substrate is at least approximately 175 mg per cubic centimeter. More preferably, the density of the aerosol-generating substrate is at least approximately 200 mg per cubic centimeter. Even more preferably, the density of the aerosol-generating substrate is at least approximately 250 mg per cubic centimeter. ocnbnn / C7n7 / e / Yi Preferably, the density of the aerosol-generating substrate is less than or equal to approximately 500 mg per cubic centimeter. More preferably, the density of the aerosol-generating substrate is less than or equal to approximately 450 mg per cubic centimeter. More preferably, the density of the aerosol-generating substrate is less than or equal to approximately 400 mg per cubic centimeter. Even more preferably, the density of the aerosol-generating substrate is less than or equal to approximately 350 mg per cubic centimeter.For example, the density of the aerosol-generating substrate is preferably from approximately 150 mg per cubic centimeter to approximately 500 mg per cubic centimeter, preferably from approximately 175 mg per cubic centimeter to approximately 450 mg per cubic centimeter, more preferably from approximately 200 mg to approximately 400 mg per cubic centimeter, and more preferably from 250 mg per cubic centimeter to 350 mg per cubic centimeter. In a particularly preferred embodiment of the invention, the density of the aerosol-generating substrate is approximately 300 mg per cubic centimeter. In certain preferred embodiments, the aerosol-generating substrate bar comprises shredded tobacco material, e.g., tobacco scraps, having a density of between approximately 150 mg per cubic centimeter and approximately 500 mg per cubic centimeter, preferably between approximately 175 mg per cubic centimeter and approximately 450 mg per cubic centimeter, more preferably between approximately 200 mg per cubic centimeter and approximately 400 mg per cubic centimeter, more preferably between approximately 250 mg per cubic centimeter and approximately 350 mg per cubic centimeter, with the highest preference, approximately 300 mg per cubic centimeter. The RTD of the aerosol-generating substrate bar is preferably less than or equal to approximately 10 millimeters of H2O. More preferably, the RTD of the aerosol-generating substrate bar is less than or equal to approximately 9 millimeters of H2O. Even more preferably, the RTD of the aerosol-generating substrate bar is less than or equal to approximately 8 millimeters of H2O. The RTD of the aerosol-generating substrate bar is preferably at least approximately 4 mm H2O. More preferably, the RTD of the aerosol-generating substrate bar is at least approximately 5 mm H2O. Even more preferably, the RTD of the aerosol-generating substrate bar is at least approximately 6 mm H2O. ocrmnn / cznz / R / vi In some embodiments, the RTD of the aerosol-generating substrate bar is approximately 4 mm H2O to approximately 10 mm H2O, preferably approximately 5 mm H2O to approximately 10 mm H2O, or preferably approximately 6 mm H2O to approximately 25 mm H2O. In other embodiments, the RTD of the aerosol-generating substrate bar is approximately 4 mm H2O to approximately 20 mm H2O, preferably approximately 5 mm H2O to approximately 18 mm H2O, or preferably approximately 6 mm H2O to approximately 16 mm H2O.In other additional modalities, the RTD of the aerosol generating substrate bar is approximately 4 millimeters of H2O to approximately 15 millimeters of H2O, preferably approximately 5 millimeters of H2O to approximately 14 millimeters of H2O, with greater preference approximately 6 millimeters of H2O to approximately 12 millimeters of H2O. The aerosol-generating substrate may be a solid aerosol-generating substrate. The aerosol-generating substrate preferably comprises an aerosol former. The aerosol former may be any suitable known compound or mixture of compounds that, during use, facilitates the formation of a dense and stable aerosol. The aerosol former may make the aerosol essentially resistant to thermal degradation at temperatures typically encountered during use of the aerosol-generating article. Suitable aerosol formers include, for example: polyhydric alcohols such as, for example, triethylene glycol, 1,3-butanediol, propylene glycol, and glycerin; esters of polyhydric alcohols such as mono-, di-, or triacetate of glycerol; and aliphatic esters of mono-, di-, or polycarboxylic acids such as, for example, dimethyl dodecanedioate and dimethyl tetradecanedioate; and combinations thereof. Preferably, the aerosol former comprises one or more glycerin and propylene glycol. The aerosol former may consist of glycerin or propylene glycol or a combination of glycerin and propylene glycol. Preferably, the aerosol generating substrate comprises at least 5 percent by weight of the aerosol former on a dry weight basis of the aerosol generating substrate, more preferably between 10 percent and 22 percent by weight on a dry weight basis of the cut aerosol generating substrate, more preferably, the amount of aerosol former is between 12 percent and 19 percent by weight on a dry weight basis of the aerosol generating substrate, further for example, the amount of aerosol former is between 13 percent and 16 percent by weight on a dry weight basis of the aerosol generating substrate. In certain preferred embodiments of the invention, the aerosol-generating substrate comprises shredded tobacco material. For example, the shredded tobacco material may be in the form of flakes, as described in more detail below. Alternatively, the shredded tobacco material may be in the form of a shredded sheet of homogenized tobacco material. Homogenized tobacco materials suitable for use in the present invention are described below. Within the context of this description, the term “chisel” is used to describe a mixture of crushed plant material, such as tobacco plant material, which includes, in particular, one or more processed leaf blades, stems and veins, homogenized plant material. The bite may also include another tobacco bite or casing. Preferably, the powder comprises at least 25 percent of the plant leaf blade, more preferably at least 50 percent, still more preferably at least 75 percent, and most preferably at least 90 percent. Preferably, the plant material is tobacco, mint, tea, or cloves. Most preferably, the plant material is tobacco. However, as will be described in more detail below, the invention is equally applicable to other plant material that has the ability to release substances upon the application of heat, which can subsequently form an aerosol. Preferably, the tobacco material comprises material from the tobacco plant, including leaves of one or more types of blond tobacco, dark tobacco, aromatic tobacco, and filler tobacco. With reference to the present invention, the term "tobacco" describes any member of the plant genus Nicotiana. Blonde tobaccos are tobaccos with generally large, light-colored leaves. Throughout this description, the term “blonde tobacco” is used for tobaccos that have been cured in an artificial atmosphere. Examples of blonde tobaccos include hot-air dried Chinese tobacco, hot-air dried Brazilian tobacco, hot-air dried American tobacco such as Virginia tobacco, hot-air dried Indian tobacco, hot-air dried Tanzanian tobacco, or other hot-air dried African tobaccos. Blonde tobacco is characterized by a high sugar-to-nitrogen ratio. From a sensory perspective, blonde tobacco is a type of tobacco that, after curing, is associated with a spicy and slightly spicy sensation. Within the context of the present invention, blonde tobaccos are tobaccos with a sugar reduction content of between approximately 2.5 percent and approximately 20 percent of the dry weight of the leaf and a total ammonia content of less than approximately 0.12 percent of the leaf dry weight basis. Reducing sugars include, for example, glucose or fructose. Total ammonia includes, for example, ammonia and ammonium salts. Dark tobaccos are tobaccos with generally large, dark-colored leaves. Throughout this description, the term "dark tobacco" refers to air-cured tobaccos. Additionally, dark tobaccos may be fermented. Tobaccos primarily used for chewing tobacco blends, snuff, cigars, and pipe tobacco are also included in this category. Typically, these dark tobaccos are air-cured and possibly fermented. From a sensory perspective, dark tobacco is a type of tobacco that, after curing, is associated with the sensation of a dark, smoky cigar. Dark tobacco is characterized by a low sugar-to-nitrogen ratio. Examples of dark tobacco include Malawi Burley or other African Burley, Dark Cured Brazilian Galpão, and Sun-Curred or Air-Cured Indonesian Kasturi.According to the invention, dark tobaccos are tobaccos with a reduced sugar content of less than approximately 5 percent on a dry weight basis of the leaf and a total ammonia content of up to approximately 0.5 percent on a dry weight basis of the leaf. Aromatic tobaccos are tobaccos that often have small, light-colored leaves. Throughout this description, the term "aromatic tobacco" is used for other tobaccos that have a high aromatic content, for example, of essential oils. From a sensory perspective, aromatic tobacco is a type of tobacco that, after curing, is associated with a spicy and aromatic sensation. Examples of aromatic tobaccos include Greek Oriental, Turkish Oriental, and Semi-Oriental tobacco, but also Fire Cured, American Burley, such as Penque, Rustica, and Meriland. Filler tobacco is not a specific type of tobacco, but rather includes types of tobacco that are primarily used to complement the other types of tobacco used in the blend and do not contribute a specific characteristic aroma to the final product. Examples of filler tobaccos are the stems, main vein, or canes of other types of tobacco.A specific example could be the hot air dried stems of the lower stem of Flue Cure Brazil. The tobacco suitable for use with the present invention generally resembles tobacco used for conventional smoking articles. The cut width of the tobacco is preferably between 0.3 mm and 2.0 mm, more preferably between 0.5 mm and 1.2 mm, and most preferably between 0.6 mm and 0.9 mm. The cut width may play a role in the heat distribution within the aerosol-generating substrate bar. Furthermore, the cut width may affect the article's suction resistance. Additionally, the cut width may affect the overall density of the aerosol-generating substrate. The length of the tobacco strand is somewhat random, as the length of the strands will depend on the overall size of the object from which the strand is cut.However, by conditioning the material before cutting, for example by controlling the moisture content and overall fineness of the material, longer strands can be cut. Preferably, the strands are between approximately 10 millimeters and approximately 40 millimeters long before being assembled to form the aerosol-generating substrate bar. Obviously, if the strands are arranged in an aerosol-generating substrate bar with a longitudinal extension where the longitudinal extension of the section is less than 40 millimeters, the final aerosol-generating substrate bar may comprise strands that are, on average, shorter than the length of the initial strand. Preferably, the length of the cutting strand is such that between approximately 20 percent and 60 percent of the strands extend along the entire length of the aerosol-generating substrate bar.This prevents the strands from easily detaching from the aerosol generating substrate bar. In preferred embodiments, the nibble weight is between 80 milligrams and 400 milligrams, preferably between 150 milligrams and 250 milligrams, with the strongest preference being between 170 milligrams and 220 milligrams. This nibble weight typically provides sufficient material for aerosol formation. Furthermore, in light of the aforementioned restrictions on diameter and size, this allows for a balanced density of the aerosol-generating substrate bar between energy absorption, suction resistance, and fluid channels within the aerosol-generating substrate bar where the aerosol-generating substrate comprises plant material. Preferably, the pit is soaked with an aerosol former. The pit soaking can be done by spraying or other suitable application methods. The aerosol former can be applied to the mixture during pit preparation. For example, the aerosol former can be applied to the mixture in the direct conditioning casing cylinder (DCCC). Conventional machinery can be used to apply an aerosol former to the pit. The aerosol former can be any suitable known compound or mixture of compounds that, during use, facilitates the formation of a dense and stable aerosol. The aerosol former can make the aerosol essentially resistant to thermal degradation at temperatures typically encountered during use of the aerosol-generating article.Suitable aerosol formers are, for example, polyhydric alcohols such as, for example, triethylene glycol, 1,3-butanediol, propylene glycol and glycerin; esters of polyhydric alcohols such as, for example, mono-, di- or triacetate of glycerol; aliphatic esters of mono-, di- or polycarboxylic acids such as, for example, dimethyl dodecanedioate and dimethyl tetradecanedioate; and combinations thereof. Preferably, the aerosol former comprises one or more glycerin and propylene glycol. The aerosol former may consist of glycerin or propylene glycol or a combination of glycerin and propylene glycol. Preferably, the amount of aerosol former is at least 5 percent by weight on a dry weight basis, preferably between 10 percent and 22 percent by weight on a dry weight basis of the sting, and more preferably between 12 percent and 19 percent by weight on a dry weight basis of the sting; for example, the amount of aerosol former is between 13 percent and 16 percent by weight on a dry weight basis of the sting. When aerosol former is added to the sting in the amounts described above, the sting may become relatively sticky.This advantageously helps to retain the bite in a predetermined location within the article, as bite particles show a tendency to adhere to surrounding bite particles as well as surrounding surfaces (e.g., the inner surface of a wrapper that circumscribes the bite). For some methods, the amount of aerosol former has a target value of approximately 13 percent by weight on a dry weight basis of the bite. The most efficient amount of aerosol former will also depend on the bite, whether it comprises plant leaf or homogenized plant material. For example, among other factors, the type of bite will determine the extent to which the aerosol former can facilitate the release of substances from the bite. For these reasons, an aerosol-generating substrate bar comprising the tobacco as described above is capable of efficiently generating a sufficient quantity of aerosol at relatively low temperatures. A temperature of between 150 and 200 degrees Celsius in the heating chamber may be sufficient for one of these tobacco pieces to generate adequate amounts of aerosol, whereas aerosol-generating devices using molded tobacco leaf sheets typically employ temperatures of approximately 250 degrees Celsius. Another advantage of operating at lower temperatures is that there is less need to cool the aerosol. Since low temperatures are generally used, a simpler cooling function may suffice. This, in turn, allows for a simpler and less complex design of the aerosol generator. In other preferred embodiments, the aerosol-generating substrate comprises homogenized plant material, preferably homogenized tobacco material. As used herein, the term “homogenized plant material” encompasses any plant material formed by the agglomeration of plant particles. For example, sheets or strips of homogenized tobacco material for the aerosol-generating substrates of the present invention can be formed by agglomerating particles of tobacco material obtained by pulverizing, crushing, or grinding plant material and optionally one or more sheets of tobacco leaf and tobacco leaf stems. The homogenized plant material can be produced by casting, extrusion, papermaking, or any other suitable processes known in the art. Homogenized plant material can be provided in any suitable form. In some embodiments, the homogenized plant material may be in the form of one or more sheets. As used herein with reference to the invention, the term “sheet” describes a sheet-like element having a width and length substantially greater than its thickness. The homogenized plant material may be in the form of a plurality of pellets or granules. The homogenized plant material may be in the form of a plurality of strands, strips, or fragments. As used herein, the term “strand” describes an elongated element of material whose length is substantially greater than its width and thickness. The term “strand” should be considered to encompass strips, shreds, and any other homogenized plant material of a similar shape. Strands of homogenized plant material may be formed from a sheet of homogenized plant material, for example, by cutting or shredding, or by other methods, such as extrusion. ocrmnn / cznz / R / vi In some embodiments, strands may form in place within the aerosol-generating substrate as a result of splitting or cracking of a sheet of homogenized plant material during substrate formation, for example, as a result of curling. The strands of homogenized plant material within the aerosol-generating substrate may separate from one another. Alternatively, each strand of homogenized plant material within the aerosol-generating substrate may be at least partially connected to one or more adjacent strands along the length of the strands. For example, adjacent strands may be connected by one or more fibers. This can occur, for example, where strands are formed due to splitting of a sheet of homogenized plant material during the production of the aerosol-generating substrate, as described above. When the homogenized plant material is in the form of one or more sheets, as described above, the sheets can be produced by a molding process. Alternatively, sheets of homogenized plant material can be produced by a papermaking process. One or more sheets described herein may each have an individual thickness of between 100 micrometers and 600 micrometers, preferably between 150 micrometers and 300 micrometers, and most preferably between 200 micrometers and 250 micrometers. Individual thickness refers to the thickness of the individual sheet, while combined thickness refers to the total thickness of all sheets comprising the aerosol-generating substrate. For example, if the aerosol-generating substrate consists of two individual sheets, then the combined thickness is either the sum of the thicknesses of the two individual sheets or the measured thickness of the two sheets where they are stacked on the aerosol-generating substrate. The one or more sheets as described in this description may each individually have a weight of between approximately 100 grams per square meter and approximately 600 grams per square meter. Each of the one or more sheets as described herein may individually have a density of approximately 0.3 grams per cubic centimeter to approximately 1.3 grams per cubic centimeter, and preferably from approximately 0.7 grams per cubic centimeter to approximately 10 grams per cubic centimeter. In embodiments of the present invention in which the aerosol-generating substrate comprises one or more sheets of homogenized plant material, the sheets are preferably in the form of one or more crinkled sheets. As used herein, the term “crinkled” denotes that the sheet of homogenized plant material is twisted, folded, or otherwise compressed or contracted essentially transversely to the cylindrical axis of a plug or rod. One or more sheets of homogenized plant material can be folded transversely in relation to their longitudinal axis and circumscribed with an envelope to form a continuous bar or a plug. One or more sheets of homogenized plant material may be advantageously curled or similarly treated. As used herein, the term “curled” refers to a sheet having a plurality of essentially parallel ridges or corrugations. The one or more sheets of homogenized plant material may be embossed, stamped, perforated, or otherwise deformed to provide texture on one or both sides of the sheet. Preferably, each sheet of homogenized plant material may be curled so that it has a plurality of ridges or corrugations essentially parallel to the cylindrical axis of the plug. This treatment advantageously facilitates the gathering of the curled sheet of homogenized plant material to form the plug. Preferably, one or more sheets of homogenized plant material may be gathered. It will be appreciated that the curled sheets of homogenized plant material may alternatively or additionally have a plurality of essentially parallel ridges or corrugations arranged at an acute or obtuse angle to the cylindrical axis of the plug. The sheet may be curled to such an extent that the integrity of the sheet is destroyed at the plurality of parallel ridges or corrugations, causing the material to separate and resulting in the formation of shreds, strands, or strips of homogenized plant material. Alternatively, one or more sheets of homogenized plant material may be cut into strands as described above. In such embodiments, the aerosol-generating substrate comprises a plurality of strands of the homogenized plant material. The strands may be used to form a plug. Typically, the width of such strands is approximately 5 millimeters, or approximately 4 millimeters, or approximately 3 millimeters, or approximately 2 millimeters or less. The length of the strands may be greater than approximately 5 millimeters, between approximately 5 millimeters and approximately 15 millimeters, from approximately 8 millimeters to approximately 12 millimeters, or approximately 12 millimeters. Preferably, the strands are essentially the same length as one another. ocrmnn / cznz / R / vi The homogenized plant material may comprise up to approximately 95 percent by weight of plant particles, on a dry weight basis. Preferably, the homogenized plant material comprises approximately 90 percent by weight of plant particles, more preferably approximately 80 percent by weight of plant particles, more preferably up to approximately 70 percent by weight of plant particles, more preferably up to approximately 60 percent by weight of plant particles, more preferably up to approximately 50 percent by weight of plant particles, on a dry weight basis. For example, homogenized plant material may comprise from approximately 2.5 percent to approximately 95 percent by weight of plant particles, or from approximately 5 percent to approximately 90 percent by weight of plant particles, or from approximately 10 percent to approximately 80 percent by weight of plant particles, or from approximately 15 percent to approximately 70 percent by weight of plant particles, or from approximately 20 percent to approximately 60 percent by weight of plant particles, or from approximately 30 percent to approximately 50 percent by weight of plant particles, on a dry weight basis. In certain embodiments of the invention, the homogenized plant material is a homogenized tobacco material comprising tobacco particles. The sheets of homogenized tobacco material for use in such embodiments of the invention may have a tobacco content of at least approximately 40 percent by weight on a dry weight basis, more preferably at least approximately 50 percent by weight on a dry weight basis, more preferably at least approximately 70 percent by weight on a dry weight basis, and most preferably at least approximately 90 percent by weight on a dry weight basis. With reference to the present invention, the term “tobacco particles” describes particles of any plant member of the genus Nicotiana. The term “tobacco particles” encompasses ground or powdered tobacco leaf flakes, ground or powdered tobacco leaf stems, tobacco powder, tobacco fines, and other particulate tobacco byproducts formed during the processing, handling, and shipping of tobacco. In a preferred embodiment, the tobacco particles are essentially all derived from tobacco leaf flakes. In contrast, isolated nicotine and nicotine salts are tobacco-derived compounds, but they are not considered tobacco particles for the purposes of the invention and are not included in the percentage of particulate plant material. The homogenized plant material may further comprise one or more aerosol formers. Upon volatilization, an aerosol former can carry other vaporized compounds released from the aerosol-generating substrate upon heating, such as nicotine and flavorings, into an aerosol. Suitable aerosol formers for inclusion in the homogenized plant material are known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, propylene glycol, 1,3-butanediol, and glycerin; esters of polyhydric alcohols, such as mono-, di-, or triacetate glycerin; and aliphatic esters of mono-, di-, or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. The homogenized plant material may have an aerosol former content of between approximately 5 percent and approximately 30 percent by weight on a dry weight basis, such as between approximately 10 percent and approximately 25 percent by weight on a dry weight basis, or between approximately 15 percent and approximately 20 percent by weight on a dry weight basis. The aerosol former may act as a wetting agent in the homogenized plant material. As previously stated, the aerosol-generating substrate bar may be enclosed by a wrapper. The wrapper enclosing the aerosol-generating substrate bar may be a paper wrapper or a non-paper wrapper. Paper wrappers suitable for use in specific embodiments of the invention are known in the art and include, but are not limited to, cigarette papers and filter cap wrappers. Non-paper wrappers suitable for use in specific embodiments of the invention are known in the art and include, but are not limited to, sheets of homogenized tobacco materials. A paper wrapper may have a basis weight of at least 15 g / m², preferably at least 20 g / m². The paper wrapper may have a basis weight of 35 g / m² or less, preferably 30 g / m² or less. The paper wrapper may have a basis weight of 15 g / m² to 35 g / m², preferably 20 g / m² to 30 g / m². In a preferred embodiment, the paper wrapper may have a basis weight of 25 g / m². A paper wrapper may have a thickness of at least 25 micrometers, preferably at least 30 micrometers, more preferably at least 35 micrometers. The paper wrapper may have a thickness of 55 micrometers or less, preferably 50 micrometers or less, more preferably 45 micrometers or less. The paper wrapping can have a thickness of 25 micrometers to 55 micrometers, preferably 30 micrometers to 50 micrometers, with greater preference for 35 micrometers to 45 micrometers.In a preferred embodiment, the paper wrapping can be 40 microns thick. In certain preferred embodiments, the envelope may be formed from a laminated material comprising a plurality of layers. Preferably, the envelope is formed from a co-laminated aluminum sheet. The use of a co-laminated sheet comprising aluminum advantageously prevents combustion of the aerosol-generating substrate in the event that the aerosol-generating substrate is to be ignited, rather than heated as intended. The paper layer of the laminated sheet may have a basis weight of at least 35 g / m², preferably at least 40 g / m². The paper layer of the laminated sheet may have a basis weight of 55 g / m² or less, preferably 50 g / m² or less. The paper layer of the laminated sheet may have a basis weight of 35 g / m² to 55 g / m², preferably 40 g / m² to 50 g / m². In a preferred embodiment, the paper layer of the laminated sheet may have a basis weight of 45 g / m². A paper layer of the co-laminated sheet may have a thickness of at least 50 micrometers, preferably at least 55 micrometers, and more preferably at least 60 micrometers. The paper layer of the co-laminated sheet may have a thickness of 80 micrometers or less, preferably 75 micrometers or less, and more preferably 70 micrometers or less. The paper layer of the laminated sheet may have a thickness of 50 micrometers to 80 micrometers, preferably 55 micrometers to 75 micrometers, with greater preference 60 micrometers to 70 micrometers. In a preferred embodiment, the paper layer of the laminated sheet may have a thickness of 65 micrometers. A metallic layer of the laminated sheet may have a basis weight of at least 12 g / m², preferably at least 15 g / m². The metallic layer of the laminated sheet may have a basis weight of 25 g / m² or less, preferably 20 g / m² or less. The metallic layer of the laminated sheet may have a basis weight of 12 g / m² to 25 g / m², preferably 15 g / m² to 20 g / m². In a preferred embodiment, the metallic layer of the laminated sheet may have a basis weight of 17 g / m². A metallic layer of the co-laminated sheet may have a thickness of at least 2 micrometers, preferably at least 3 micrometers, more preferably at least 5 micrometers. The metallic layer of the co-laminated sheet may have a thickness less than or equal to 15 micrometers, preferably less than or equal to 12 micrometers, more preferably less than or equal to 10 micrometers. The metallic layer of the laminated sheet can have a thickness of 2 micrometers to 15 micrometers, preferably from 3 micrometers to 12 micrometers, with greater preference from 5 micrometers to 10 micrometers. In a preferred embodiment, the metallic layer of the laminated sheet can have a thickness of 6 micrometers. The wrapper enclosing the aerosol-generating substrate bar can be a paper wrapper comprising PVOH (polyvinyl alcohol) or silicon. The addition of PVOH (polyvinyl alcohol) or silicon can improve the grease barrier properties of the wrapper. PVOH or silicon can be applied to the paper layer as a surface coating, such as on an outer surface of the paper layer of the wrapper enclosing the aerosol-generating substrate bar. PVOH or silicon can be applied and form a layer on the outer surface of the paper layer of the wrapper. PVOH or silicon can be applied on an inner surface of the paper layer of the wrapper. PVOH or silicon can be applied and form a layer on the inner surface of the paper layer of the aerosol-generating article. PVOH or silicon can be applied on both the inner and outer surfaces of the paper layer of the wrapper. PVOH or silicon can be applied and form a layer on both the inner and outer surfaces of the paper layer of the wrapper. The paper wrapping comprising PVOH or silicon may have a basis weight of at least 20 g / m², preferably at least 25 g / m², and more preferably at least 30 g / m². The paper wrapping comprising PVOH or silicon may have a basis weight of 50 g / m² or less, preferably 45 g / m² or less, and more preferably 40 g / m² or less. The paper wrapping comprising PVOH or silicon may have a basis weight of 20 g / m² to 50 g / m², preferably 25 g / m² to 45 g / m², and more preferably 30 g / m² to 40 g / m². In particularly preferred embodiments, the paper wrapping comprising PVOH or silicon may have a basis weight of approximately 35 g / m². The paper wrapping comprising PVOH or silicone may have a thickness of at least 25 micrometers, preferably at least 30 micrometers, and more preferably at least 35 micrometers. The paper wrapping comprising PVOH or silicone may have a thickness of 50 micrometers or less, preferably 45 micrometers or less, and more preferably 40 micrometers or less. The paper wrapping comprising PVOH or silicone may have a thickness of 25 to 50 micrometers, preferably 30 to 45 micrometers, and more preferably 35 to 40 micrometers. In particularly preferred embodiments, the paper wrapping comprising PVOH or silicone may have a thickness of 37 micrometers. The envelope surrounding the aerosol-generating substrate bar may comprise a flame-retardant composition comprising one or more flame-retardant compounds. The term "flame-retardant compounds" is used herein to describe chemical compounds that, when added to or otherwise incorporated into a carrier substrate, such as paper or plastic compounds, provide the carrier substrate with varying degrees of protection against flammability. In practice, flame-retardant compounds may be activated by the presence of an ignition source and are adapted to prevent or slow the further development of ignition through a variety of different physical and chemical mechanisms. A flame-retardant composition may typically further comprise one or more non-flame-retardant compounds, i.e., one or more compounds, such as a solvent, excipient, or filler, that do not actively contribute to providing flammability protection to the carrier substrate but are used to facilitate the application of the flame-retardant compound(s) onto or within the wrapping, or both. Some of the non-flame-retardant compounds in a flame-retardant composition, such as solvents, are volatile and may evaporate from the wrapping after drying, once the flame-retardant composition has been applied to or within the wrapping base material, or both.As such, although these non-flame retardant compounds are part of the formulation of the flame retardant composition, they may no longer be present or may only be detectable in trace amounts on the packaging of an aerosol-generating article. Those skilled in the art are familiar with a number of suitable flame retardant compounds. In particular, several flame retardant compounds and formulations suitable for the treatment of cellulosic materials are known and have been described, and can be used in the manufacture of packaging for aerosol-generating articles according to the present invention. For example, the flame retardant composition may comprise a polymer and a mixed salt based on at least one mono-, di- and / or tricarboxylic acid, at least one polyphosphoric, pyrophosphoric and / or phosphoric acid, and a hydroxide or salt of an alkali or alkaline earth metal, wherein at least one mono-, di- and / or tricarboxylic acid and the hydroxide or salt form a carboxylate and at least one polyphosphoric, pyrophosphoric and / or phosphoric acid and the hydroxide or salt form a phosphate. ocnt?nn / C7n7 / e / Yi Preferably, the flame retardant composition may further comprise an alkali metal carbonate or an earth metal alloy. Alternatively, the flame retardant composition may comprise cellulose modified with at least one CIO or higher fatty acid, tall oil fatty acid (TOFA), phosphorylated linseed oil, or downstream phosphorylated corn oil. Preferably, at least one CIO or higher fatty acid is selected from the group consisting of capric acid, myristic acid, palmitic acid, and combinations thereof. In a wrapper comprising a flame-retardant composition suitable for use in an aerosol-generating article according to the present invention, the flame-retardant composition may be provided in a treated portion of the wrapper. This means that the flame-retardant composition has been applied on or within a corresponding portion of a wrapper base material, or both. Therefore, in the treated portion, the wrapper has a total dry basis weight that is greater than the dry basis weight of the wrapper base material.The treated portion of the wrapper may extend over at least approximately 10 percent of the external surface area of ​​the aerosol-generating substrate bar circumscribed by the wrapper, preferably over at least approximately 20 percent of the external surface area of ​​the aerosol-generating substrate bar circumscribed by the wrapper, more preferably over at least approximately 40 percent of the external surface area of ​​the aerosol-generating substrate bar, and still more preferably over at least approximately 60 percent of the external surface area of ​​the aerosol-generating substrate bar. Most preferably, the treated portion of the wrapper extends over at least approximately 80 percent of the external surface area of ​​the aerosol-generating substrate bar.In particularly preferred embodiments, the treated portion of the wrap extends over at least approximately 90 or even 95 percent of the external surface area of ​​the aerosol-generating substrate bar. With the highest preference, the treated portion of the wrap extends essentially over the entire external surface area of ​​the aerosol-generating substrate bar. The wrapping comprising a flame-retardant composition may have a basis weight of at least 20 g / m², preferably at least 25 g / m², and more preferably at least 30 g / m². The wrapping comprising a flame-retardant composition may have a basis weight of 45 g / m² or less, preferably 40 g / m² or less, and more preferably 35 g / m² or less. The wrapping comprising a flame-retardant composition may have a basis weight of 20 g / m² to 45 g / m², preferably 25 g / m² to 40 g / m², and more preferably 35 g / m² to 35 g / m². In some preferred embodiments, the wrapping comprising a flame-retardant composition may have a basis weight of 33 g / m². The envelope comprising a flame-retardant composition may have a thickness of at least 25 micrometers, preferably at least 30 micrometers, and even more preferably 35 micrometers. The envelope comprising a flame-retardant composition may have a thickness of 50 micrometers or less, preferably 45 micrometers or less, and even more preferably 40 micrometers or less. In some embodiments, the envelope comprising a flame-retardant composition may have a thickness of 37 micrometers. An aerosol-generating article according to this description preferably comprises an upstream section located upstream of the aerosol-generating substrate bar. The upstream section is preferably located immediately upstream of the aerosol-generating substrate bar. The upstream section preferably extends between the upstream end of the aerosol-generating article and the aerosol-generating substrate bar. The upstream section may comprise one or more upstream elements located upstream of the aerosol-generating substrate bar. Such one or more upstream elements are described herein. The aerosol-generating articles of the present invention preferably comprise an upstream element located upstream of and adjacent to the aerosol-generating substrate. The upstream element advantageously prevents direct physical contact with the upstream end of the aerosol-generating substrate. For example, when the aerosol-generating substrate comprises a susceptor element, the upstream element can prevent direct physical contact with the upstream end of the susceptor element. This helps prevent displacement or deformation of the susceptor element during handling or transport of the aerosol-generating article. This, in turn, helps to fix the shape and position of the susceptor element. Furthermore, the presence of an upstream element helps prevent any loss of the substrate, which may be advantageous, for example, if the substrate contains particulate plant material. When the aerosol-generating substrate comprises shredded tobacco, such as tobacco chips, the upstream section or element thereof may further help to prevent the loss of loose tobacco particles from the upstream end of the article. The upstream section, or upstream element thereof, can also provide an additional degree of protection to the aerosol-generating substrate during storage, as it covers at least to some extent the upstream end of the aerosol-generating substrate, which may otherwise be exposed. For aerosol-generating articles intended to be inserted into a cavity in an aerosol-generating device so that the aerosol-generating substrate can be heated externally within the cavity, the upstream section, or upstream element, can advantageously facilitate the insertion of the article's upstream end into the cavity. The inclusion of the upstream element can further protect the end of the aerosol-generating substrate bar during insertion of the article into the cavity, thus minimizing the risk of damage to the substrate. The upstream section, or the upstream element thereof, can also provide an enhanced appearance to the upstream end of the aerosol-generating item. Additionally, if desired, the upstream section, or the upstream element thereof, can be used to provide information about the aerosol-generating item, such as brand, flavor, contents, or details of the aerosol-generating device for which the item is intended. An upstream element may be a porous plug element. Preferably, an upstream element has a porosity of at least approximately 50 percent in the longitudinal direction of the aerosol-generating article. More preferably, an upstream element has a porosity of between approximately 50 percent and approximately 90 percent in the longitudinal direction. The porosity of an upstream element in the longitudinal direction is defined by the ratio of the cross-sectional area of ​​the material forming the upstream element to the internal cross-sectional area of ​​the aerosol-generating article at the position of the upstream element. An upstream element may be made of a porous material or may comprise a plurality of openings. This can be achieved, for example, through laser perforation. Preferably, the plurality of openings is evenly distributed over the cross-section of the upstream element. The porosity or permeability of an upstream element can be advantageously designed to provide an aerosol-generating article with a particular total resistance to aspiration (RTD) without essentially affecting the filtration provided by other portions of the article. An upstream element may be made of an airtight material. In such embodiments, the aerosol-generating article may be configured so that air flows to the aerosol-generating substrate bar through suitable ventilation means provided in an enclosure. In certain preferred embodiments of the invention, it may be desirable to minimize the RTD of an upstream element. For example, this may be the case for articles intended to be inserted into the cavity of an aerosol generating device such that the aerosol generating substrate is heated externally, as described herein. For such articles, it is desirable to provide the article with as much RTD as possible, so that most of the RTD experience for the consumer is provided by the aerosol generating device and not the article. The RTD of the upstream element is preferably less than or equal to approximately 10 millimeters of H2O. More preferably, the RTD of the upstream element is less than or equal to approximately 5 millimeters of H2O. Even more preferably, the RTD of the upstream element is less than or equal to approximately 2.5 millimeters of H2O. Still more preferably, the RTD of the upstream element is less than or equal to approximately 2 millimeters of H2O. The RTD of an upstream element can be at least 0.1 millimeters of H2O, or at least approximately 0.25 millimeters of H2O, or at least approximately 0.5 millimeters of H2O. In some embodiments, the RTD of an upstream element is approximately 0.1 mm H2O to approximately 10 mm H2O, preferably approximately 0.25 mm H2O to approximately 10 mm H2O, and preferably approximately 0.5 mm H2O to approximately 10 mm H2O. In other embodiments, the RTD of an upstream element is approximately 0.1 mm H2O to approximately 5 mm H2O, preferably approximately 0.25 mm H2O to approximately 5 mm H2O, and preferably approximately 0.5 mm H2O to approximately 5 mm H2O. In further embodiments, the RTD of an upstream element is approximately 0.1 mm H2O to approximately 2.5 mm H2O, preferably approximately 0.25 mm H2O to approximately 2.5 mm H2O, with the most preference being approximately 0.5 mm H2O to approximately 2.5 mm H2O. In additional embodiments, the RTD of an upstream element is approximately 0.1 mm H2O to approximately 2 mm H2O, preferably approximately 0.25 mm H2O to approximately 2 mm H2O, with greater preference approximately 0.5 mm H2O to approximately 2 mm H2O. In a particularly preferred embodiment, the RTD of an upstream element is approximately 1 mm H2O. Preferably, an upstream element has an RTD of less than approximately 2 millimeters of H2O per millimeter of length, more preferably less than approximately 1.5 millimeters of H2O per millimeter of length, more preferably less than approximately 1 millimeter of H2O per millimeter of length, more preferably less than approximately 0.5 millimeters of H2O per millimeter of length, more preferably less than approximately 0.3 millimeters of H2O per millimeter of length, more preferably less than approximately 0.2 millimeters of H2O per millimeter of length. Preferably, the combined RTD of the upstream section, or upstream element thereof, and the aerosol-generating substrate bar is less than approximately 15 millimeters of H2O, more preferably less than approximately 12 millimeters of H2O, more preferably less than approximately 10 millimeters of H2O. In particularly preferred embodiments, an upstream element is formed from a hollow tubular segment that defines a longitudinal cavity providing an unrestricted flow channel. In such embodiments, an upstream element can provide protection for the aerosol-generating substrate, as described above, while having minimal effect on the overall resistance to suction (RTD) and filtration properties of the article. Preferably, the diameter of the longitudinal cavity of the hollow tubular segment forming an upstream element is at least approximately 4 millimeters, more preferably at least approximately 4.5 millimeters, more preferably at least approximately 5 millimeters, and more preferably at least approximately 5.5 millimeters.Preferably, the diameter of the longitudinal cavity is maximized to minimize the RTD of the upstream section, or upstream element. An internal diameter of the upstream element can be approximately 5.1 mm. Preferably, the wall thickness of the hollow tubular segment is less than approximately 2 millimeters, more preferably less than approximately 1.5 millimeters, and more preferably less than approximately 1.25 millimeters. The wall thickness of the hollow tubular segment defining an upstream element may be approximately 1 mm. An upstream element of the upstream section may be made of any material suitable for use in an aerosol-generating article. The upstream element may be manufactured, for example, from the same material used for one of the other components of the aerosol-generating article, such as the nozzle, cooling element, or support element. Suitable materials for forming the upstream element include filter materials, ceramics, polymeric material, cellulose acetate, cardboard, zeolite, or aerosol-generating substrate. The upstream element may comprise a cellulose acetate plug. The upstream element may comprise a hollow acetate tube or a cardboard tube. Preferably, an upstream element is made of a heat-resistant material. For example, preferably an upstream element is made of a material that withstands temperatures up to 350 degrees Celsius. This ensures that an upstream element is not adversely affected by the heating means used to heat the aerosol-generating substrate. Preferably, the upstream section, or an upstream element thereof, has an outside diameter that is approximately equal to the outside diameter of the aerosol-generating article. Preferably, the outside diameter of the upstream section, or an upstream element thereof, is between approximately 6 mm and approximately 8 mm, more preferably between approximately 7 mm and approximately 7.5 mm. Preferably, the upstream section, or an upstream element thereof, has an outside diameter of approximately 7.1 mm. Preferably, the upstream section or an upstream element has a length of between approximately 2 millimeters and approximately 8 millimeters, more preferably between approximately 3 millimeters and approximately 7 millimeters, and more preferably between approximately 4 millimeters and approximately 6 millimeters. In a particularly preferred embodiment, the upstream section or an upstream element has a length of approximately 5 millimeters. The length of the upstream section or an upstream element can be advantageously varied to provide the desired overall length of the aerosol-generating article. For example, when it is desired to reduce the length of one of the other components of the aerosol-generating article, the length of the upstream section or an upstream element can be increased to maintain the same overall length of the article. Furthermore, the length of the upstream section, or an element upstream of it, can be used to control the position of the aerosol-generating item within the cavity of an aerosol-generating device, for items intended to be heated externally. This can advantageously ensure that the position of the aerosol-generating substrate within the cavity can be optimized for heating, and the position of any ventilation can also be optimized. The upstream section is preferably enclosed by an envelope, such as a plug envelope. The envelope enclosing the upstream section is preferably a rigid plug envelope, for example, a plug envelope having a basis weight of at least 80 grams per square meter (g / m²), or at least approximately 100 g / m², or at least approximately 110 g / m². This provides structural rigidity to the upstream section. The upstream section is preferably connected to the aerosol generating substrate bar and optionally to at least a portion of the downstream section by means of an external enclosure, as described herein. As mentioned above, an aerosol-generating article according to the present invention comprises a downstream section located downstream of the aerosol-generating substrate bar. The downstream section is preferably located immediately downstream of the aerosol-generating substrate bar. The downstream section of the aerosol-generating article preferably extends between the aerosol-generating substrate bar and the downstream end of the aerosol-generating article. The downstream section may comprise one or more elements, each of which will be described in more detail herein. The length of the downstream section can be at least approximately 20 mm. The length of the downstream section can be at least approximately 24 mm. The length of the downstream section can be at least approximately 26 mm. The length of the downstream section can be equal to or less than (in other words, it cannot be greater than) approximately 36 mm. The length of the downstream section can be equal to or less than approximately 32 mm. The length of the downstream section can be equal to or less than approximately 30 mm. The length of the downstream section can be between approximately 20 mm and approximately 36 mm. The length of the downstream section can be between approximately 24 mm and approximately 32 mm. The length of the downstream section can be between approximately 26 mm and approximately 30 mm. ocnwin / cznz / e / Yi Preferably, the downstream section comprises a hollow tubular element. Preferably, the downstream section comprises a nozzle element. In preferred embodiments of the present invention, the downstream section comprises, or consists of, a hollow tubular element and a nozzle element, wherein the hollow tubular element is located between the aerosol-generating substrate bar and the nozzle element. In embodiments where the downstream section comprises a hollow tubular element and a nozzle element, the combined or total length of the hollow tubular element and the nozzle element may be at least approximately 20 mm. In other words, the sum of the lengths of the hollow tubular element and the nozzle element may be at least approximately 20 mm. A combined length of the hollow tubular element and the nozzle element may be at least approximately 24 mm. A combined length of the hollow tubular element and the nozzle element may be at least approximately 26 mm. The combined length of the hollow tubular element and the nozzle element may be equal to or less than approximately 36 mm. The combined length of the hollow tubular element and the nozzle element may be equal to or less than approximately 32 mm. The combined length of the hollow tubular element and the nozzle element may be equal to or less than approximately 30 mm. The combined length of the hollow tubular element and the nozzle element can be between approximately 20 mm and approximately 36 mm. The combined length of the hollow tubular element and the nozzle element can be between approximately 24 mm and approximately 32 mm. The combined length of the hollow tubular element and the nozzle element can be between approximately 26 mm and approximately 30 mm. Preferably, a combined length of the hollow tubular element and the nozzle element can be approximately 28 mm. In configurations where the downstream section consists of a hollow tubular element and a nozzle element, the length of the downstream section is defined by the combined length of the hollow tubular element and the nozzle element. Providing a relatively long downstream section, which can be defined by a relatively long combination of the hollow tubular element and the nozzle element, ensures that an adequate length of the aerosol-generating article protrudes from an aerosol-generating device when the article is received. Such an adequate protrusion length facilitates the ease of insertion and removal of the article from the device, and also ensures that the upstream portions of the article are properly inserted into the device with less risk of damage, particularly during insertion. The ratio of the downstream section length to the total length of the aerosol-generating article may be less than or equal to approximately 0.80. Preferably, the ratio of the downstream section length to the total length of the aerosol-generating article may be less than or equal to approximately 0.75. More preferably, the ratio of the downstream section length to the total length of the aerosol-generating article may be less than or equal to approximately 0.70. Even more preferably, the ratio of the downstream section length to the total length of the aerosol-generating article may be less than or equal to approximately 0.65. The ratio of the downstream section length to the total length of the aerosol-generating article may be at least approximately 0.30. Preferably, the ratio of the downstream section length to the total length of the aerosol-generating article may be at least approximately 0.40. More preferably, the ratio of the downstream section length to the total length of the aerosol-generating article may be at least approximately 0.50. Even more preferably, the ratio of the downstream section length to the total length of the aerosol-generating article may be at least approximately 0.60. In some embodiments, the ratio of the downstream section length to the total length of the aerosol-generating article is approximately 0.30 to approximately 0.80, preferably approximately 0.40 to approximately 0.80, more preferably approximately 0.50 to approximately 0.80, and even more preferably approximately 0.60 to approximately 0.80. In other embodiments, the ratio of the downstream section length to the total length of the aerosol-generating article is approximately 0.30 to approximately 0.75, preferably approximately 0.40 to approximately 0.75, more preferably approximately 0.50 to approximately 0.75, and even more preferably approximately 0.60 to approximately 0.75. In additional embodiments, the ratio of the downstream section length to the total length of the aerosol-generating article is approximately 0.30 to approximately 0.70, preferably from approximately 0.40 to approximately 0.70, more preferably from approximately 0.50 to approximately 0.70, and more preferably from approximately 0.60 to approximately 0.70. For example, a ratio between a length of the downstream section and a total length of the aerosol generating article may be between approximately 0.60 and 0.65, more preferably a ratio between a length of the downstream section and a total length of the aerosol generating article may be 0.62. The ratio of the downstream section length to the upstream section length may be less than or equal to approximately 18. Preferably, the ratio of the downstream section length to the upstream section length may be less than or equal to approximately 12. More preferably, the ratio of the downstream section length to the upstream section length may be less than or equal to approximately 8. Even more preferably, the ratio of the downstream section length to the upstream section length may be less than or equal to approximately 6. The ratio of the downstream section length to the upstream section length may be at least approximately 2.5. Preferably, the ratio of the downstream section length to the upstream section length may be at least approximately 3. More preferably, the ratio of the downstream section length to the upstream section length may be at least approximately 4. Even more preferably, the ratio of the downstream section length to the upstream section length may be at least approximately 5. In some embodiments, the ratio of downstream section length to upstream section length is approximately 2.5 to approximately 18, preferably approximately 3 to approximately 18, more preferably approximately 4 to approximately 18, and even more preferably approximately 5 to approximately 18. In other embodiments, the ratio of downstream section length to upstream section length is approximately 2.5 to approximately 12, preferably approximately 3 to approximately 12, more preferably approximately 4 to approximately 12, and even more preferably approximately 5 to approximately 12. In additional embodiments, the ratio of downstream section length to upstream section length is approximately 2.5 to approximately 8, preferably from approximately 3 to approximately 8, with greater preference from approximately 4 to approximately 8, even more preferably from approximately 5 to approximately 8. As an example, a ratio between a length of ocnt?nn / C7n7 / e / Yi the downstream section and a length of the upstream section may be approximately 6, even more preferably approximately 5.6. The ratio of the length of the aerosol-generating element (in other words, the aerosol-generating substrate bar) to the length of the downstream section may be less than or equal to approximately 0.80. Preferably, the ratio of the length of the aerosol-generating element to the length of the downstream section may be less than or equal to approximately 0.70. More preferably, the ratio of the length of the aerosol-generating element to the length of the downstream section may be less than or equal to approximately 0.60. Even more preferably, the ratio of the length of the aerosol-generating element to the length of the downstream section may be less than or equal to approximately 0.50. The ratio of the length of the aerosol-generating element to the length of the downstream section may be at least approximately 0.20. Preferably, the ratio of the length of the aerosol-generating element to the length of the downstream section may be at least approximately 0.25. More preferably, the ratio of the length of the aerosol-generating element to the length of the downstream section may be at least approximately 0.30. Even more preferably, the ratio of the length of the aerosol-generating element to the length of the downstream section may be at least approximately 0.40. In some embodiments, the ratio of the length of the aerosol-generating element to the length of the downstream section is approximately 0.20 to approximately 0.80, preferably approximately 0.25 to approximately 0.80, more preferably approximately 0.30 to approximately 0.80, and even more preferably approximately 0.40 to approximately 0.80. In other embodiments, the ratio of the length of the aerosol-generating element to the length of the downstream section is approximately 0.20 to approximately 0.70, preferably approximately 0.25 to approximately 0.70, more preferably approximately 0.30 to approximately 0.70, and even more preferably approximately 0.40 to approximately 0.70. In additional embodiments, the ratio of the length of the aerosol-generating element to the length of the downstream section is approximately 0.20 to approximately 0.60, preferably from approximately 0.25 to approximately 0.60, more preferably from approximately 0.30 to approximately 0.60, and more preferably from approximately 0.40 to approximately 0.60. For example, a ratio between a length of the aerosol generating element and a length of the downstream section may be approximately 0.5, more preferably approximately 0.45, and more preferably approximately 0.43. The downstream section of an aerosol-generating article according to the present invention may comprise a hollow tubular element. The hollow tubular element is preferably provided downstream of the aerosol-generating substrate bar. The hollow tubular element may be provided immediately downstream of the aerosol-generating substrate bar. In other words, the hollow tubular element may abut a downstream end of the aerosol-generating substrate bar. The hollow tubular element may define an upstream end of the downstream section of the aerosol-generating article. The hollow tubular element may be located between the aerosol-generating substrate bar and the downstream end of the aerosol-generating article. The downstream end of the aerosol-generating article may coincide with the downstream end of the downstream section.Preferably, the downstream section of the aerosol-generating article comprises a single hollow tubular element. In other words, the downstream section of the aerosol-generating article may comprise only one hollow tubular element. As used throughout this description, the terms hollow tubular segment or hollow tubular element denote a generally elongated element that defines an airflow passage or lumen along its longitudinal axis. In particular, the term tubular will be used hereafter with reference to a tubular element having an essentially cylindrical cross-section and defining at least one airflow duct that establishes uninterrupted, continuous communication between an upstream end of the tubular element and a downstream end of the tubular element. However, it is understood that alternative geometries of the tubular segment (e.g., alternative cross-sectional shapes) may be possible. The hollow tubular segment or element may be a discrete, individual component of the aerosol-generating article having a defined length and thickness. The internal volume defined by the hollow tubular element can be at least approximately 100 cubic millimeters. In other words, the volume of the cavity or lumen defined by the hollow tubular element can be at least approximately 100 cubic millimeters. Preferably, the internal volume defined by the hollow tubular element can be at least approximately 300 cubic millimeters. The internal volume defined by the hollow tubular element can be at least approximately 700 cubic millimeters. ocnt?nn / C7n7 / e / Yi The internal volume defined by the hollow tubular element may be less than or equal to approximately 1,200 cubic millimeters. Preferably, the internal volume defined by the hollow tubular element may be less than or equal to approximately 1,000 cubic millimeters. The internal volume defined by the hollow tubular element may be less than or equal to approximately 900 cubic millimeters. The internal volume defined by the hollow tubular element can be between approximately 100 and approximately 1,200 cubic millimeters. Preferably, the internal volume defined by the hollow tubular element can be between approximately 300 and approximately 1,000 cubic millimeters. The internal volume defined by the hollow tubular element can be between approximately 700 and approximately 900 cubic millimeters. In the context of the present invention, a hollow tubular segment provides an unrestricted flow channel. This means that the hollow tubular segment provides a negligible level of resistance to suction (RTD). The term “negligible RTD” is used to describe an RTD of less than 1 mm H2O per 10 millimeters of length of the hollow tubular segment or hollow tubular element, preferably less than approximately 0.4 mm H2O per 10 millimeters of length of the hollow tubular segment or hollow tubular element, and more preferably less than approximately 0.1 mm H2O per 10 millimeters of length of the hollow tubular segment or hollow tubular element. The RTD of the hollow tubular element is preferably less than or equal to approximately 10 mm H2O. More preferably, the RTD of the hollow tubular element is less than or equal to approximately 5 mm H2O. Even more preferably, the RTD of the hollow tubular element is less than or equal to approximately 2.5 mm H2O. Even more preferably, the RTD of the hollow tubular element is less than or equal to approximately 2 mm H2O. Even more preferably, the RTD of the hollow tubular element is less than or equal to approximately 1 mm H2O. The RTD of a hollow tubular element can be at least approximately 0 millimeters of H2O, or at least approximately 0.25 millimeters of H2O, or at least approximately 0.5 millimeters of H2O, or at least approximately 1 millimeter of H2O. In some embodiments, the RTD of a hollow tubular element is approximately 0 mm H2O to approximately 10 mm H2O, preferably approximately 0.25 mm H2O to approximately 10 mm H2O, or preferably approximately 0.5 mm H2O to approximately 10 mm H2O. In other embodiments, the RTD of a hollow tubular element is approximately 0 mm H2O to approximately 5 mm H2O, preferably approximately 0.25 mm H2O to approximately 5 mm H2O, or preferably approximately 0.5 mm H2O to approximately 5 mm H2O. In other embodiments, the RTD of a hollow tubular element is approximately 1 mm H2O to approximately 5 mm H2O. In additional modalities, the RTD of a hollow tubular element is approximately 0 millimeters H2O to approximately 2.5 millimeters H2O, preferably from approximately 0.25 millimeters H2O to approximately 2.5 mm H2O, with a higher preference of approximately 0.5 mm H2O to approximately 2.5 mm H2O. In additional embodiments, the RTD of a hollow tubular element is approximately 0 mm H2O to approximately 2 mm H2O, preferably approximately 0.25 mm H2O to approximately 2 mm H2O, with a higher preference of approximately 0.5 mm H2O to approximately 2 mm H2O. In a particularly preferred embodiment, the RTD of a hollow tubular element is approximately 0 mm H2O. In aerosol-generating articles according to the present invention, the overall RTD of the article depends essentially on the RTD of the boom and, optionally, on the RTD of the nozzle and / or upstream elements. This is because the hollow tubular segment is essentially empty and, as such, contributes only marginally to the overall RTD of the aerosol-generating article. Therefore, the flow channel must be free of any component that obstructs airflow in a longitudinal direction. Preferably, the flow channel is essentially empty. In the present description, a “hollow tubular segment” or “hollow tubular element” may also be referred to as a “hollow tube” or “hollow tube segment”. The hollow tubular element may comprise one or more hollow tubular segments. Preferably, the hollow tubular element consists of a single hollow tubular segment. Preferably, the hollow tubular element consists of a continuous hollow tubular segment. A hollow tubular segment may comprise any of the features described herein in relation to the hollow tubular element. As will be described in greater detail within this description, the aerosol-generating article may comprise a vent zone at a location along the downstream section. More specifically, the aerosol-generating article may comprise a vent zone at a location along the hollow tubular element. Such, or any, vent zone may extend through the peripheral wall of the hollow tubular element. As such, continuous communication is established between the flow channel defined internally by the hollow tubular element and the external environment. The vent zone is further described within this description. The length of the hollow tubular element can be at least approximately 15 mm. The length of the hollow tubular element can be at least approximately 17 mm. The length of the hollow tubular element can be at least approximately 19 mm. The length of the hollow tubular element may be less than or equal to approximately 30 mm. The length of the hollow tubular element may be less than or equal to approximately 25 mm. The length of the hollow tubular element may be less than or equal to approximately 23 mm. The length of the hollow tubular element can be between approximately 15 mm and 30 mm. The length of the hollow tubular element can be between approximately 17 mm and 25 mm. The length of the hollow tubular element can be between approximately 19 mm and 23 mm. Preferably, the length of the hollow tubular element can be approximately 21 mm. A relatively long, hollow tubular element provides and defines a relatively long internal cavity within the aerosol-generating article and downstream of the aerosol-generating substrate bar. As described herein, providing an empty cavity downstream (preferably immediately downstream) of the aerosol-generating substrate enhances the nucleation of aerosol particles generated by the substrate. Providing a relatively long cavity maximizes these nucleation benefits, thereby improving aerosol formation and cooling. The ratio of the length of the aerosol-generating element (in other words, the aerosol-generating substrate bar) to the length of the hollow tubular element may be less than or equal to approximately 1.25. Preferably, the ratio of the length of the aerosol-generating element to the length of the hollow tubular element may be less than or equal to approximately 1. More preferably, the ratio of the length of the aerosol-generating element to the length of the hollow tubular element may be less than or equal to approximately 0.75. Even more preferably, the ratio of the length of the aerosol-generating element to the length of the hollow tubular element may be less than or equal to approximately 0.60. The ratio of the length of the aerosol generating element to the length of the hollow tubular element may be at least approximately 0.25. Preferably, the ratio of the length of the aerosol generating element to the length of the hollow tubular element may be at least approximately 0.30. More preferably, the ratio of the length of the aerosol generating element to the length of the hollow tubular element may be at least approximately 0.40. Even more preferably, the ratio of the length of the aerosol generating element to the length of the hollow tubular element may be at least approximately 0.50. In some embodiments, the ratio of the length of the aerosol-generating element to the length of the hollow tubular element is approximately 0.25 to approximately 1.25, preferably approximately 0.30 to approximately 1.25, more preferably approximately 0.40 to approximately 1.25, and even more preferably approximately 0.50 to approximately 1.25. In other embodiments, the ratio of the length of the aerosol-generating element to the length of the hollow tubular element is approximately 0.25 to approximately 1, preferably approximately 0.30 to approximately 1, more preferably approximately 0.40 to approximately 1, and even more preferably approximately 0.50 to approximately 1. In additional embodiments, the ratio of the length of the aerosol-generating element to the length of the hollow tubular element is approximately 0.25 to approximately 0.75, preferably approximately 0.30 to approximately 0.75, with a higher preference of approximately 0.40 to approximately 0.75, with an even higher preference of approximately 0.50 to approximately 0.75. As an example, a ratio between a length of the aerosol generating element and a length of the hollow tubular element may be approximately 0.6, with a higher preference of approximately 0.57. The ratio of the length of the hollow tubular element to the length of the downstream section may be less than or equal to approximately 1. Preferably, the ratio of the length of the hollow tubular element to the length of the downstream section may be less than or equal to approximately 0.90. More preferably, the ratio of the length of the hollow tubular element to the length of the downstream section may be less than or equal to approximately 0.85. Even more preferably, the ratio of the length of the hollow tubular element to the length of the downstream section may be less than or equal to approximately 0.80. The ratio of the length of the hollow tubular element to the length of the downstream section may be at least approximately 0.35. Preferably, the ratio of the length of the hollow tubular element to the length of the downstream section may be at least approximately 0.45. More preferably, the ratio of the length of the hollow tubular element to the length of the downstream section may be at least approximately 0.50. Even more preferably, the ratio of the length of the hollow tubular element to the length of the downstream section may be at least approximately 0.60. In some embodiments, the ratio of the length of the hollow tubular element to the length of the downstream section is approximately 0.35 to approximately 1, preferably approximately 0.45 to approximately 1, more preferably approximately 0.50 to approximately 1, and even more preferably approximately 0.60 to approximately 1. In other embodiments, the ratio of the length of the hollow tubular element to the length of the downstream section is approximately 0.35 to approximately 0.90, preferably approximately 0.45 to approximately 0.90, more preferably approximately 0.50 to approximately 0.90, and even more preferably approximately 0.60 to approximately 0.90. In additional embodiments, the ratio of the length of the hollow tubular element to the length of the downstream section is approximately 0.35 to approximately 0.85, preferably approximately 0.45 to approximately 0.85, with a higher preference of approximately 0.50 to approximately 0.85, with an even higher preference of approximately 0.60 to approximately 0.85. As an example, a ratio between a length of the hollow tubular element and a length of the downstream section may preferably be approximately 0.75. The ratio of the length of the hollow tubular element to the total length of the aerosol-generating article may be less than or equal to approximately 0.80. Preferably, the ratio of the length of the hollow tubular element to the total length of the aerosol-generating article may be less than or equal to approximately 0.70. More preferably, the ratio of the length of the hollow tubular element to the total length of the aerosol-generating article may be less than or equal to approximately 0.60. Even more preferably, the ratio of the length of the hollow tubular element to the total length of the aerosol-generating article may be less than or equal to approximately 0.50. The ratio of the length of the hollow tubular element to the total length of the aerosol-generating article may be at least approximately 0.25. Preferably, the ratio of the length of the hollow tubular element to the total length of the aerosol-generating article may be at least approximately 0.30. More preferably, the ratio of the length of the hollow tubular element to the total length of the aerosol-generating article may be at least approximately 0.40. Even more preferably, the ratio of the length of the hollow tubular element to the total length of the aerosol-generating article may be at least approximately 0.45. In some embodiments, the ratio of the length of the hollow tubular element to the total length of the aerosol-generating article is approximately 0.25 to approximately 0.80, preferably approximately 0.30 to approximately 0.80, more preferably approximately 0.40 to approximately 0.80, and even more preferably approximately 0.45 to approximately 0.80. In some embodiments, the ratio of the length of the hollow tubular element to the total length of the aerosol-generating article is approximately 0.25 to approximately 0.70, preferably approximately 0.30 to approximately 0.70, more preferably approximately 0.40 to approximately 0.70, and even more preferably approximately 0.45 to approximately 0.70. In additional embodiments, the ratio of the length of the hollow tubular element to the total length of the aerosol-generating article is approximately 0.25 to approximately 0.60, preferably from approximately 0.30 to approximately 0.60, with greater preference from approximately 0.40 to approximately 0.60, and even more preferentially from approximately 0.45 to approximately 0.60. As an example, a ratio between a length of the hollow tubular element and a total length of the aerosol generating article may be approximately 0.5, with greater preference from approximately 0.47. Providing a downstream section or hollow tubular element with the ratios listed above maximizes the cooling and aerosol-forming benefits of having a relatively long hollow tubular element while providing sufficient filtration for an aerosol-generating item designed to heat up, not burn up. Furthermore, providing a longer hollow tubular element can advantageously reduce the effective RTD of the downstream section of the aerosol-generating item, which would be primarily defined by the RTD of a nozzle filtration element. The thickness of a peripheral wall (in other words, the wall thickness) of the hollow tubular element can be at least approximately 100 micrometers. The wall thickness of the hollow tubular element can be at least approximately 150 micrometers. The wall thickness of the hollow tubular element can be at least approximately 200 micrometers, preferably at least approximately 250 micrometers, and even more preferably at least approximately 500 micrometers (or 0.5 mm). The wall thickness of the hollow tubular element may be less than or equal to approximately 2 millimeters, preferably less than or equal to approximately 1.5 millimeters, and even more preferably less than or equal to approximately 1.25 mm. The wall thickness of the hollow tubular element may be less than or equal to approximately 1 millimeter. The wall thickness of the hollow tubular element may be less than or equal to approximately 500 micrometers. The wall thickness of the hollow tubular element can be between approximately 100 micrometers and approximately 2 millimeters, preferably between approximately 150 micrometers and approximately 1.5 millimeters, even more preferably between approximately 200 micrometers and approximately 1.25 millimeters. The wall thickness of the hollow tubular element can preferably be approximately 250 micrometers (approximately 0.25 mm). At the same time, keeping the peripheral wall thickness of the hollow tubular element relatively low ensures that the total internal volume of the hollow tubular element, which is available for the aerosol to begin the nucleation process as soon as the aerosol components leave the aerosol-generating substrate bar, and the cross-sectional surface area of ​​the hollow tubular element are effectively maximized, while at the same time ensuring that the hollow tubular element has the necessary structural strength to prevent the collapse of the aerosol-generating item as well as to provide some support to the aerosol-generating substrate bar, and that the RTD of the hollow tubular element is minimized.It is understood that larger cross-sectional surface areas of the hollow tubular element cavity are associated with a reduced aerosol stream velocity along the aerosol-generating element, which is also expected to promote aerosol nucleation. Furthermore, it appears that using a relatively thin hollow tubular element essentially prevents the diffusion of ventilation air before it comes into contact with and mixes with the aerosol stream, which is also understood to further promote nucleation. In practice, by providing more controllable, localized cooling of the vaporized species stream, it is possible to enhance the cooling effect on the formation of new aerosol particles. ocnt?nn / C7n7 / e / Yi The hollow tubular element preferably has an outer diameter that is approximately equal to the outer diameter of the aerosol-generating substrate bar and the outer diameter of the aerosol-generating article. The hollow tubular element can have an outside diameter of between 5 millimeters and 12 millimeters, for example, between 5 millimeters and 10 millimeters or between 6 millimeters and 8 millimeters. In a preferred embodiment, the hollow tubular element has an outside diameter of 7.2 millimeters plus or minus 10 percent. The hollow tubular element may have an internal diameter. Preferably, the hollow tubular element may have a constant internal diameter along its length. However, the internal diameter of the hollow tubular element may vary along its length. The hollow tubular element may have an internal diameter of at least approximately 2 millimeters. For example, the hollow tubular element may have an internal diameter of at least approximately 4 millimeters, at least approximately 5 millimeters, or at least approximately 7 millimeters. Providing a hollow tubular element having an internal diameter as previously established can advantageously provide sufficient stiffness and strength to the hollow tubular element. The hollow tubular element may have an internal diameter of no more than approximately 10 millimeters. For example, the hollow tubular element may have an internal diameter of no more than approximately 9 millimeters, no more than approximately 8 millimeters, or no more than approximately 7.5 millimeters. Providing a hollow tubular element having an internal diameter as previously established can advantageously reduce the suction resistance of the hollow tubular element. The hollow tubular element can have an internal diameter of between approximately 2 millimeters and approximately 10 millimeters, between approximately 4 millimeters and approximately 9 millimeters, between approximately 5 millimeters and approximately 8 millimeters, or between approximately 6 millimeters and approximately 7.5 millimeters. The hollow tubular element may have an outer diameter of approximately 7.1 or 7.2 mm. The hollow tubular element may have an inner diameter of approximately 6.7 mm. The ratio between an internal diameter of the hollow tubular element and the external diameter of the hollow tubular element can be at least approximately 0.8. For example, the ratio between an internal diameter of the hollow tubular element and the external diameter of the hollow tubular element can be at least approximately 0.85, at least approximately 0.9, or at least approximately 0.95. The ratio between an internal diameter of the hollow tubular element and the external diameter of the hollow tubular element may not be greater than approximately 0.99. For example, the ratio between an internal diameter of the hollow tubular element and the external diameter of the hollow tubular element may not be greater than approximately 0.98. The ratio between an internal diameter of the hollow tubular element and the external diameter of the hollow tubular element can be approximately 0.97. Providing a relatively large internal diameter can advantageously reduce the suction resistance of the hollow tubular element and improve the cooling and nucleation of aerosol particles. The lumen or cavity of the hollow tubular element can have any cross-sectional shape. The lumen of the hollow tubular element can have a circular cross-sectional shape. The hollow tubular element may comprise a paper-based material. The hollow tubular element may comprise at least one layer of paper. The paper may be very rigid. The paper may be corrugated paper, such as heat-resistant corrugated paper or corrugated parchment paper. Preferably, the hollow tubular element may comprise cardboard. The hollow tubular element may be a cardboard tube. The hollow tubular element may be formed from cardboard. Advantageously, cardboard is a cost-effective material that provides a balance between being deformable to facilitate insertion of the item into an aerosol generating device and being rigid enough to ensure proper coupling of the item with the device's interior. Therefore, a cardboard tube can provide adequate resistance to deformation or compression during use. The hollow tubular element may be a paper tube. The hollow tubular element may be a tube formed from spirally wound paper. The hollow tubular element may be formed from a plurality of paper layers. The paper may have a basis weight of at least approximately 50 grams per square meter, at least approximately 60 grams per square meter, at least approximately 70 grams per square meter, or at least approximately 90 grams per square meter. ocnt?nn / C7n7 / e / Yi The hollow tubular element may comprise a polymeric material. For example, the hollow tubular element may comprise a polymeric film. The polymeric film may comprise a cellulose film. The hollow tubular element may comprise low-density polyethylene (LDPE) or polyhydroxyalkanoate (PHA) fibers. The hollow tubular element may comprise cellulose acetate tow. When the hollow tubular element comprises cellulose acetate tow, the cellulose acetate tow may have a denier per filament of between approximately 2 and approximately 4 and a total denier of between approximately 25 and approximately 40. In some embodiments, the aerosol-generating article according to the present invention may comprise a ventilation zone at a location along the downstream section. More specifically, in those embodiments where the downstream section comprises a hollow tubular element, the ventilation zone may be provided at a location along the hollow tubular element. As such, a vented cavity is provided downstream of the aerosol-generating substrate bar. This provides several potential technical benefits. First, the inventors have found that one of these ventilated hollow tubular elements provides particularly efficient cooling of the aerosol. Therefore, satisfactory aerosol cooling can be achieved even through a relatively short downstream section. This is especially convenient as it allows for the provision of an aerosol-generating device in which an aerosol-generating substrate (and particularly one containing tobacco) is heated rather than burned, combining satisfactory aerosol delivery with efficient cooling of the aerosol to temperatures desirable for the consumer.Second, the inventors have surprisingly discovered how such rapid cooling of the volatile species released by heating the aerosol-generating substrate promotes enhanced nucleation of the aerosol particles. This effect is particularly noticeable when, as will be described in more detail below, the vent zone is located at a precisely defined position along the length of the hollow tubular element relative to other components of the aerosol-generating article. Indeed, the inventors have found that the beneficial effect of enhanced nucleation is able to significantly counteract the potentially less desirable effects of dilution induced by the introduction of ventilation air. ocrmnn / oznz / R / vi The distance between the ventilation zone and an upstream end of the aerosol-generating article may be at least 25 millimeters. As used herein, the term “distance between the ventilation zone and another element or portion of the aerosol-generating article” refers to a distance measured in the longitudinal direction, that is, in a direction extending along, or parallel to, the cylindrical axis of the aerosol-generating article. Preferably, the distance between the ventilation zone and an upstream end of the aerosol-generating article is at least 26 millimeters. More preferably, the distance between the ventilation zone and an upstream end of the aerosol-generating article is at least 27 millimeters. The distance between the ventilation zone and an upstream end of the aerosol-generating article may be less than or equal to 34 millimeters. Preferably, the distance between the ventilation zone and an upstream end of the aerosol-generating article is less than or equal to 33 millimeters. More preferably, the distance between the ventilation zone and an upstream end of the aerosol-generating article is less than or equal to 31 millimeters. In some embodiments, the distance between the ventilation zone and an upstream end of the aerosol-generating article is 25 millimeters to 34 millimeters, preferably 26 millimeters to 34 millimeters, with greater preference 27 millimeters to 34 millimeters. In other embodiments, the distance between the ventilation zone and an upstream end of the aerosol-generating article is 25 millimeters to 33 millimeters, preferably 26 millimeters to 33 millimeters, with greater preference 27 millimeters to 33 millimeters. In additional embodiments, the distance between the ventilation zone and an upstream end of the aerosol-generating article is 25 millimeters to 31 millimeters, preferably 26 millimeters to 31 millimeters, with greater preference 27 millimeters to 31 millimeters. In some particularly preferred embodiments, the distance between the ventilation zone and an upstream end of the aerosol-generating article is 28 millimeters to 30 millimeters. It has been found that aerosol-generating articles comprising a ventilation zone at a location along the hollow tubular element at a distance from an upstream end of the aerosol-generating article that falls within the intervals described above offer multiple benefits. First, it has been observed that such articles provide particularly satisfactory aerosol supplies to the consumer, particularly where the aerosol-generating substrate comprises tobacco. Without wishing to limit ourselves to theory, the intense cooling caused by ambient air drawn into the cavity of the hollow tubular element in the ventilation zone is understood to accelerate the condensation of aerosol former droplets (e.g., glycerin) that have been released from the aerosol-generating substrate upon heating. In turn, the volatilized nicotine and organic acids similarly released from the tobacco substrate accumulate on the newly formed aerosol former droplets and subsequently combine into nicotine salts. Consequently, the overall ratio of aerosol particle phase to aerosol gas phase can be improved compared to existing aerosol-generating devices. Positioning the venting zone upstream of the aerosol-generating article, as described above, advantageously reduces the flight time of the vaporized nicotine before the nicotine particles reach the aerosol former droplets. At the same time, this positioning of the venting zone upstream of the aerosol-generating article ensures sufficient time and space for nicotine accumulation and nicotine salt formation to occur to a significant degree before the aerosol stream reaches the consumer's mouth. The ventilation zone typically comprises a plurality of perforations through the peripheral wall of the hollow tubular element. Preferably, the ventilation zone comprises at least one circumferential row of perforations. In some embodiments, the ventilation zone may comprise two circumferential rows of perforations. For example, the perforations may be formed in a line during the manufacture of the aerosol-generating article. Preferably, each circumferential row of perforations comprises from 8 to 30 perforations. An aerosol-generating article according to the present invention may have a ventilation level of at least approximately 2 percent. The term “vent level” is used throughout this specification to indicate a volume ratio between the airflow admitted into the aerosol-generating article through the vent zone (vent airflow) and the sum of the aerosol airflow and the vent airflow. The higher the vent level, the greater the dilution of the aerosol delivered to the consumer. The aerosol-generating article preferably has a vent level of at least 5 percent, more preferably at least 10 percent, and even more preferably at least 12 percent or at least 15 percent. An aerosol-generating article according to the present invention may have a ventilation level of up to approximately 90 percent. Preferably, an aerosol-generating article according to the present invention has a ventilation level of less than or equal to 80 percent, more preferably less than or equal to 70 percent, still more preferably less than or equal to 60 percent, with the lowest preference greater than or equal to 50 percent. Therefore, an aerosol-generating article according to the present invention may have a ventilation level of 2% to 90%, preferably 5% to 90%, more preferably 10% to 90%, and even more preferably 15% to 90%. An aerosol-generating article according to the present invention may have a ventilation level of 2% to 80%, preferably 5% to 80%, more preferably 10% to 80%, and even more preferably 15% to 80%. An aerosol-generating article according to the present invention may have a ventilation level of 2% to 70%, preferably 5% to 70%, more preferably 10% to 70%, and even more preferably 15% to 70%.An aerosol-generating article according to the present invention may have a ventilation level of 2% to 60%, preferably 5% to 60%, more preferably 10% to 60%, and even more preferably 15% to 60%. An aerosol-generating article according to the present invention may have a ventilation level of 2% to 50%, preferably 5% to 50%, more preferably 10% to 50%, and even more preferably 15% to 50%. The aerosol-generating article preferably has a ventilation level of 30% or less, preferably 25% or less, more preferably 20% or less, and even more preferably 18% or less. In some embodiments, the aerosol-generating article has a ventilation level of 10 to 30 percent, preferably 12 to 30 percent, with a higher preference of 15 to 30 percent. In other embodiments, the aerosol-generating article has a ventilation level of 10 to 25 percent, preferably 12 to 25 percent, with a higher preference of 15 to 25 percent. In further embodiments, the aerosol-generating article has a ventilation level of 10 to 20 percent, preferably 12 to 20 percent, with a higher preference of 15 to 20 percent. In particularly preferred embodiments, the aerosol-generating article has a ventilation level of 10 to 18 percent, preferably 12 to 18 percent, with a higher preference of 15 to 18 percent. ocrmnn / oznz / R / vi Without intending to impose any theory, the inventors have found that the temperature drop caused by the entry of cooler outside air into the hollow tubular element through the ventilation zone can have an advantageous effect on the nucleation and growth of aerosol particles. The formation of an aerosol from a gaseous mixture containing several chemical species depends on a delicate interplay between nucleation, evaporation, and condensation, as well as coalescence, while also explaining variations in concentration fields, temperature, and vapor velocity. The so-called classical theory of nucleation is based on the assumption that a fraction of the molecules in the gas phase are large enough to remain coherent for a long time with a sufficient probability (e.g., a probability of half). These molecules represent a kind of critical threshold molecule cluster among transient molecular aggregates, meaning that, on average, smaller molecule clusters are likely to disintegrate fairly quickly in the gas phase, while larger clusters are likely to grow.This critical cluster is identified as the key nucleation nucleus from which droplets are expected to grow due to the condensation of vapor molecules. Naive droplets that have just nucleated are assumed to emerge with a certain original diameter and can then grow by several orders of magnitude. This is facilitated and can be enhanced by rapid cooling of the surrounding vapor, which induces condensation. In this regard, it is important to note that evaporation and condensation are two sides of the same mechanism, namely gas-liquid mass transfer. While evaporation refers to the net mass transfer from the liquid droplets to the gas phase, condensation is the net mass transfer from the gas phase to the droplet phase. Evaporation (or condensation) will cause the droplets to shrink (or grow), but it will not change the number of droplets. In this scenario, which can be further complicated by coalescence phenomena, temperature and cooling rate can play a critical role in determining how the system responds. In general, different cooling rates can lead to significantly different temporal behaviors with respect to liquid phase (droplet) formation because the nucleation process is typically nonlinear. Without adhering strictly to theory, it is hypothesized that cooling can cause a rapid increase in droplet concentration, followed by a sharp, short-lived increase in droplet growth (nucleation burst). This nucleation burst would appear to be more significant at lower temperatures. Furthermore, it would seem that higher cooling rates may favor an earlier onset of nucleation.Conversely, a reduction in the cooling rate would appear to have a favorable effect on the final size that the aerosol droplets eventually reach. Therefore, the rapid cooling induced by the intake of outside air into the hollow tubular element through the ventilation zone can be advantageously used to promote the nucleation and growth of aerosol droplets. However, at the same time, the intake of outside air into the hollow tubular element has the immediate drawback of diluting the aerosol stream delivered to the consumer. The inventors have surprisingly discovered how the beneficial effect of enhanced nucleation promoted by the rapid cooling induced by the introduction of ventilation air into the article is able to significantly counteract the less desirable effects of dilution. As such, satisfactory aerosol delivery values ​​are consistently achieved with aerosol-generating articles according to the invention. The inventors have also surprisingly found that the dilution effect on the aerosol, which can be assessed by measuring, in particular, the effect on the delivery of the aerosol former (e.g., glycerol) included in the aerosol-generating substrate, is advantageously minimized when the ventilation level is within the ranges described above. In particular, ventilation levels between 10 percent and 20 percent, and even more preferably between 12 and 18 percent, have been found to lead to particularly satisfactory glycerol delivery values. This is particularly advantageous with short aerosol-generating articles, such as those where the length of the aerosol-generating substrate bar is less than approximately 40 millimeters, preferably less than 30 millimeters, even more preferably less than 25 millimeters, and particularly preferably less than 20 millimeters, or where the overall length of the aerosol-generating article is less than approximately 70 millimeters, preferably less than approximately 60 millimeters, even more preferably less than 50 millimeters. As will be appreciated, in such aerosol-generating articles, there is typically little time and space for the aerosol to form and for the aerosol particle phase to be available for delivery to the consumer, and therefore the benefits of enhanced nucleation described above are felt particularly significantly. ocnt?nn / C7n7 / e / Yi Furthermore, because the ventilated hollow tubular element does not substantially contribute to the overall RTD of the aerosol-generating article, in aerosol-generating articles according to the invention, the overall RTD of the article can be advantageously adjusted by adjusting the length and density of the aerosol-generating substrate bar or the length and optionally the length and density of any segment of filter material forming part of the downstream section, such as a nozzle element, or the length and density of a segment of filter material provided upstream of the aerosol-generating substrate and the susceptor element. Therefore, aerosol-generating articles with a predetermined RTD can be consistently and accurately manufactured so that satisfactory RTD levels can be provided to the consumer even in the presence of ventilation. The distance between the vent zone and a downstream end of the aerosol-generating substrate bar may be at least 4 mm, 6 mm, or 8 mm. Preferably, the distance between the vent zone and a downstream end of the aerosol-generating substrate bar is at least 9 mm. More preferably, the distance between the vent zone and a downstream end of the aerosol-generating substrate bar is at least 10 mm. The distance between the vent zone and a downstream end of the aerosol-generating substrate bar is preferably less than 17 millimeters. More preferably, the distance between the vent zone and a downstream end of the aerosol-generating substrate bar is less than 16 millimeters. Even more preferably, the distance between the vent zone and a downstream end of the aerosol-generating substrate bar is less than 16 millimeters. In particularly preferred embodiments, the distance between the vent zone and a downstream end of the aerosol-generating substrate bar is less than 15 millimeters. In some embodiments, the distance between the ventilation zone and a downstream end of the aerosol-generating substrate bar is 4 to 17 millimeters, preferably 7 to 17 millimeters, with a higher preference of 10 to 17 millimeters. In other embodiments, the distance between the ventilation zone and a downstream end of the aerosol-generating substrate bar is 8 to 6 millimeters, preferably 9 to 16 millimeters, with a higher preference of 10 to 16 millimeters. In additional embodiments, the distance between the ventilation zone and a downstream end of the aerosol-generating substrate bar is 8 to 15 millimeters, preferably 9 to 15 millimeters, with a higher preference of 10 to 15 millimeters.As an example, the distance between the vent zone and a downstream end of the aerosol-generating substrate bar can be 10 to 14 millimeters, preferably 10 to 13 millimeters, with 10 to 12 millimeters being the most preferred. Positioning the vent zone within the ranges described above has the benefit of generally ensuring that, during use, the vent zone is just outside the heating device when the aerosol-generating item is inserted. Additionally, positioning the vent zone within the ranges described above has been found to advantageously improve aerosol nucleation, formation, and delivery. The distance between the ventilation zone and a downstream end of the hollow tubular element may be at least 3 millimeters. Preferably, the distance between the ventilation zone and a downstream end of the hollow tubular element is at least 5 millimeters. More preferably, the distance between the ventilation zone and a downstream end of the hollow tubular element is at least 7 millimeters. The distance between the ventilation zone and a downstream end of the hollow tubular element is preferably less than or equal to 14 millimeters. More preferably, the distance between the ventilation zone and a downstream end of the hollow tubular element is less than or equal to 12 millimeters. Even more preferably, the distance between the ventilation zone and a downstream end of the hollow tubular element is less than or equal to 10 millimeters. In some embodiments, the distance between the ventilation zone and a downstream end of the hollow tubular element is 3 to 14 millimeters, preferably 5 to 14 millimeters, with a higher preference for 7 to 14 millimeters. In additional embodiments, the distance between the ventilation zone and a downstream end of the hollow tubular element is 3 to 12 millimeters, preferably 5 to 12 millimeters, with a higher preference for 7 to 12 millimeters. In other embodiments, the distance between the ventilation zone and a downstream end of the hollow tubular element is 3 to 10 millimeters, preferably 5 to 10 millimeters, with a higher preference for 7 to 10 millimeters. ocnt?nn / C7n7 / e / Yi Positioning the vent zone downstream of the hollow tubular element within the intervals described above generally ensures that, during use, the vent zone is just outside the heating device when the aerosol-generating item is inserted. Additionally, positioning the vent zone downstream of the hollow tubular element within the intervals described above has been found to advantageously lead to the formation and delivery of a comparatively more homogeneous aerosol. The distance between the ventilation zone and a downstream end of the aerosol-generating article may be at least 10 millimeters. Preferably, the distance between the ventilation zone and a downstream end of the aerosol-generating article is at least 12 millimeters. More preferably, the distance between the ventilation zone and a downstream end of the aerosol-generating article is at least 15 millimeters. The distance between the ventilation zone and a downstream end of the aerosol-generating article is preferably less than or equal to 21 millimeters. More preferably, the distance between the ventilation zone and a downstream end of the aerosol-generating article is less than or equal to 19 millimeters. Even more preferably, the distance between the ventilation zone and a downstream end of the aerosol-generating article is less than or equal to 17 millimeters. In some embodiments, the distance between the ventilation zone and a downstream end of the aerosol-generating article is 10 to 21 millimeters, preferably 12 to 21 millimeters, and more preferably 15 to 21 millimeters. In additional embodiments, the distance between the ventilation zone and a downstream end of the aerosol-generating article is 10 to 19 millimeters, preferably 12 to 19 millimeters, and more preferably 15 to 19 millimeters. In further embodiments, the distance between the ventilation zone and a downstream end of the aerosol-generating article is 10 to 17 millimeters, preferably 12 to 17 millimeters, and more preferably 15 to 17 millimeters. Positioning the vent zone at a distance from one end downstream of the aerosol-generating article within the intervals described above generally ensures that, during use, when the aerosol-generating article is partially received into the heating device, a portion of the article extending outside the heating device is long enough for the consumer to comfortably hold the article between their lips. At the same time, evidence suggests that if the length of the portion of the aerosol-generating article extending outside the heating device is greater, it may become easy to inadvertently and inconveniently bend the article, which could impair the aerosol delivery or the intended use of the article. As described herein, the downstream section may comprise a nozzle element. The nozzle element may extend from a downstream end of the downstream section. The nozzle element may be located at the downstream end of the aerosol-generating article. The downstream end of the nozzle element may define the downstream end of the aerosol-generating article. The nozzle element may be provided downstream of the aerosol-generating substrate bar. The nozzle element may extend the entire length of the aerosol-generating article to one end of the mouthpiece. The nozzle element may comprise at least one nozzle filter segment formed from a fibrous filter material. The nozzle element may be located downstream of a hollow tubular element, as described above. The nozzle element may extend between the hollow tubular element and the downstream end of the aerosol-generating article. The nozzle element may be provided immediately downstream of the hollow tubular element. In other words, the nozzle element may abut a downstream end of the hollow tubular element. The nozzle element may define a downstream end of the downstream section of the aerosol-generating article. The parameters or characteristics described in relation to the nozzle element as a whole can equally be applied to a nozzle filter segment of the nozzle element. The fibrous filter material can be used to filter the aerosol generated from the aerosol-generating substrate. Suitable fibrous filter materials would be known to those skilled in the art. Particularly preferably, at least one nozzle filter segment comprises a cellulose acetate filter segment made of cellulose acetate tow. In certain preferred embodiments, the nozzle element consists of a single nozzle filter segment. In alternative embodiments, the nozzle element includes two or more axially aligned nozzle filter segments in an adjacent end-to-end relationship to each other. ocnt?nn / C7n7 / e / Yi In certain embodiments of the invention, the downstream section may comprise a mouth-side end cavity at the downstream end of the nozzle element as described above. The mouth-side end cavity may be defined by another hollow tubular element provided at the downstream end of the nozzle. Alternatively, the mouth-side end cavity may be defined by an outer envelope of the aerosol-generating article, wherein the outer envelope extends in a downstream direction from (or beyond) the nozzle element. The nozzle element may optionally comprise a flavoring, which may be provided in any suitable form. For example, the nozzle element may comprise one or more capsules, beads, or granules of a flavoring, or one or more flavor-loaded threads or filaments. Preferably, the nozzle element, or the nozzle filter segment thereof, has a low particle filtration efficiency. Preferably, the nozzle element is enclosed by a cap shroud. Preferably, the nozzle element is not vented so that air does not enter the aerosol-generating article along the nozzle element. The nozzle element is preferably connected to one or more of the upstream adjacent components of the aerosol generating article by means of a tip wrap. The nozzle element preferably has an outside diameter that is approximately equal to the outside diameter of the aerosol-generating article. The diameter of a nozzle element (or nozzle filter segment) may be essentially the same as the outside diameter of the hollow tubular element. As mentioned in this description, the outside diameter of the hollow tubular element may be approximately 7.2 mm, plus or minus 10 percent. The nozzle element diameter can be between approximately 5 mm and approximately 10 mm. The nozzle element diameter can be between approximately 6 mm and approximately 8 mm. The nozzle element diameter can be between approximately 7 mm and approximately 8 mm. The nozzle element diameter can be approximately 7.2 mm, plus or minus 10 percent. The nozzle element diameter can be approximately 7.25 mm, plus or minus 10 percent. Unless otherwise specified, the resistance to suction (RTD) of a component or aerosol-generating article is measured in accordance with ISO 6565-2015. RTD refers to the pressure required to force air through the entire length of a component. The terms “pressure drop” or “resistance to suction” of a component or article may also refer to “resistance to suction.” Such terms generally refer to measurements in accordance with ISO 6565-2015 that are normally carried out under test at a volumetric flow rate of approximately 17.5 milliliters per second at the outlet or downstream end of the measured component at a temperature of approximately 22 degrees Celsius, a pressure of approximately 101 kPa (approximately 760 Torr), and a relative humidity of approximately 60%. The resistance to suction (RTD) of the downstream section can be at least approximately 0 mm H2O. The RTD of the downstream section can be at least approximately 3 mm H2O. The RTD of the downstream section can be at least approximately 6 mm H2O. The RTD of the downstream section cannot be greater than approximately 12 mm H2O. The RTD of the downstream section cannot be greater than approximately 11 mm H2O. The RTD of the downstream section cannot be greater than approximately 10 mm H2O. The suction resistance of the downstream section may be greater than or equal to approximately 0 mm H2O and less than approximately 12 mm H2O. Preferably, the suction resistance of the downstream section may be greater than or equal to approximately 3 mm H2O and less than approximately 12 mm H2O. The suction resistance of the downstream section may be greater than or equal to approximately 0 mm H2O and less than approximately 11 mm H2O. Even more preferably, the suction resistance of the downstream section may be greater than or equal to approximately 3 mm H2O and less than approximately 11 mm H2O. Even more preferably, the suction resistance of the downstream section may be greater than or equal to approximately 6 mm H2O and less than approximately 10 mm H2O. Preferably, the suction resistance of the downstream section may be approximately 8 mm H2O. The resistance to suction (RTD) characteristics of the downstream section can be attributed wholly or primarily to the RTD characteristics of the nozzle element in the downstream section. In other words, the RTD of the nozzle element in the downstream section can completely define the RTD of the downstream section. The resistance to suction (RTD) of the nozzle element can be at least approximately 0 mm H2O. The RTD of the nozzle element can be at least approximately 3 mm H2O. The RTD of the nozzle element can be at least approximately 6 mm H2O. The RTD of the nozzle element may not be greater than approximately 12 mm H2O. The RTD of the nozzle element may not be greater than approximately 11 mm H2O. The RTD of the nozzle element may not be greater than approximately 10 mm H2O. The suction resistance of the nozzle element may be greater than or equal to approximately 0 mm H2O and less than approximately 12 mm H2O. Preferably, the suction resistance of the nozzle element may be greater than or equal to approximately 3 mm H2O and less than approximately 12 mm H2O. The suction resistance of the nozzle element may be greater than or equal to approximately 0 mm H2O and less than approximately 11 mm H2O. Even more preferably, the suction resistance of the nozzle element may be greater than or equal to approximately 3 mm H2O and less than approximately 11 mm H2O. Even more preferably, the suction resistance of the nozzle element may be greater than or equal to approximately 6 mm H2O and less than approximately 10 mm H2O. Preferably, the suction resistance of the nozzle element may be approximately 8 mm H2O. As mentioned previously, the nozzle element, or nozzle filter segment, can be made of a fibrous material. It can also be made of a porous material, a biodegradable material, or a cellulose material such as cellulose acetate. For example, a nozzle element can be formed from a bundle of cellulose acetate fibers with a denier per filament of approximately 10 to 15. Another example is a nozzle element formed from relatively low-density cellulose acetate tow, such as cellulose acetate tow comprising fibers of approximately 12 denier per filament. The nozzle element may be made of a polylactic acid-based material. The nozzle element may be made of a bioplastic material, preferably a starch-based bioplastic material. The nozzle element may be manufactured by injection molding or extrusion. Bioplastic-based materials are advantageous because they are capable of providing nozzle element structures that are simple and inexpensive to manufacture with a particular and complex cross-sectional profile, which may comprise a plurality of relatively large airflow channels extending through the nozzle element material, providing suitable RTD characteristics. The nozzle element can be formed from a sheet of suitable material that has been curled, pleated, gathered, woven, or folded into an element defining a plurality of longitudinally extending channels. Such a sheet of suitable material can be made of paper, cardboard, a polymer such as polylactic acid, or any other paper-based or cellulose-based material or bioplastic material. A cross-sectional profile of such a nozzle element can show the channels as being randomly oriented. The nozzle element can be formed in any other suitable way. For example, the nozzle element can be formed from an assembly of longitudinally extending tubes. The longitudinally extending tubes can be formed from polylactic acid. The nozzle element can be formed by extrusion, molding, rolling, injection, or crushing of a suitable material. Therefore, a low pressure drop (or RTD) from an upstream end of the nozzle element to a downstream end of the nozzle element is preferred. The nozzle element length may be at least approximately 3 mm. The nozzle element length may be at least approximately 5 mm. The nozzle element length may be equal to or less than approximately 11 mm. The nozzle element length may be equal to or less than approximately 9 mm. The nozzle element length may be between approximately 3 mm and approximately 11 mm. The nozzle element length may be between approximately 5 mm and approximately 9 mm. Preferably, the nozzle element length may be approximately 7 mm. The ratio of a nozzle element length to a downstream section length may be less than or equal to approximately 0.55. Preferably, the ratio of a nozzle element length to a downstream section length may be less than or equal to approximately 0.45. More preferably, the ratio of a nozzle element length to a downstream section length may be less than or equal to approximately 0.35. Even more preferably, the ratio of a nozzle element length to a downstream section length may be less than or equal to approximately 0.25. The ratio of a nozzle element length to a downstream section length may be at least approximately 0.05. Preferably, the ratio of a nozzle element length to a downstream section length may be at least approximately 0.10. More preferably, the ratio of a nozzle element length to a downstream section length may be at least approximately 0.15. Even more preferably, the ratio of a nozzle element length to a downstream section length may be at least approximately 0.20. In some embodiments, the ratio of the nozzle element length to the downstream section length is approximately 0.05 to approximately 0.55, preferably approximately 0.10 to approximately 0.55, more preferably approximately 0.15 to approximately 0.55, and even more preferably approximately 0.20 to approximately 0.55. In other embodiments, the ratio of the nozzle element length to the downstream section length is approximately 0.05 to approximately 0.45, preferably approximately 0.10 to approximately 0.45, more preferably approximately 0.15 to approximately 0.45, and even more preferably approximately 0.20 to approximately 0.45. In additional embodiments, the ratio of the nozzle element length to the downstream section length is approximately 0.05 to approximately 0.35, preferably approximately 0.10 to approximately 0.35, with greater preference from approximately 0.15 to approximately 0.35, and even more preferentially from approximately 0.20 to approximately 0.35. As an example, a ratio between a nozzle element length and a downstream section length may preferably be between approximately 0.20 and approximately 0.25, with greater preference a ratio between a nozzle element length and a downstream section length may be approximately 0.25. The ratio of the nozzle element length to the total length of the aerosol-generating article may be less than or equal to approximately 0.40. Preferably, the ratio of the nozzle element length to the total length of the aerosol-generating article may be less than or equal to approximately 0.30. More preferably, the ratio of the nozzle element length to the total length of the aerosol-generating article may be less than or equal to approximately 0.25. Still more preferably, the ratio of the nozzle element length to the total length of the aerosol-generating article may be less than or equal to approximately 0.20. ocrmnn / cznz / R / vi The ratio of the nozzle element length to the total length of the aerosol-generating article may be at least approximately 0.05. Preferably, the ratio of the nozzle element length to the total length of the aerosol-generating article may be at least approximately 0.07. More preferably, the ratio of the nozzle element length to the total length of the aerosol-generating article may be at least approximately 0.10. Even more preferably, the ratio of the nozzle element length to the total length of the aerosol-generating article may be at least approximately 0.15. In some embodiments, the ratio of the nozzle element length to the total length of the aerosol-generating article is approximately 0.05 to approximately 0.40, preferably approximately 0.07 to approximately 0.40, more preferably approximately 0.10 to approximately 0.40, and even more preferably approximately 0.15 to approximately 0.40. In other embodiments, the ratio of the nozzle element length to the total length of the aerosol-generating article is approximately 0.05 to approximately 0.30, preferably approximately 0.07 to approximately 0.30, more preferably approximately 0.10 to approximately 0.30, and even more preferably approximately 0.15 to approximately 0.30. In additional embodiments, the ratio of the nozzle element length to the total length of the aerosol-generating article is approximately 0.05 to approximately 0.25, preferably from approximately 0.07 to approximately 0.25, with greater preference from approximately 0.10 to approximately 0.25, and even more preferentially from approximately 0.15 to approximately 0.25. For example, a ratio between a nozzle element length and a total length of the aerosol generating article may be between approximately 0.15 and approximately 0.20, with greater preference from approximately 0.16. In embodiments where the downstream section comprises a hollow tubular element and a nozzle element, the ratio of the length of the hollow tubular element to the length of the nozzle element may be at least approximately 1.25. In other words, the length of the hollow tubular element may be equivalent to approximately 125% of the nozzle length. The ratio of the length of the hollow tubular element to the length of the nozzle element may be at least approximately 1.5. The ratio of the length of the hollow tubular element to the length of the nozzle element may be at least approximately 2. The ratio of the length of the hollow tubular element to the length of the nozzle element may be equal to or less than approximately 8.5. The ratio of the length of the hollow tubular element to the length of the nozzle element may be equal to or less than approximately 6. The ratio of the length of the hollow tubular element to the length of the nozzle element may be equal to or less than approximately 4. The ratio of the length of the hollow tubular element to the length of the nozzle element can be between approximately 1.25 and approximately 8.5. The ratio of the length of the hollow tubular element to the length of the nozzle element can be between approximately 1.5 and approximately 6. The ratio of the length of the hollow tubular element to the length of the nozzle element can be between approximately 2 and approximately 4. Preferably, the ratio of the length of the hollow tubular element to the length of the nozzle element can be approximately 3. In such a modality, the length of the hollow tubular element is approximately 21 mm and the length of the nozzle element is approximately 7 mm. The aerosol generating item can have a total length of approximately 35 millimeters to approximately 100 millimeters. Preferably, the overall length of an aerosol-generating article according to the invention is at least approximately 38 millimeters. More preferably, the overall length of an aerosol-generating article according to the invention is at least approximately 40 millimeters. Even more preferably, the overall length of an aerosol-generating article according to the invention is at least approximately 42 millimeters. The overall length of an aerosol-generating article according to the invention is preferably less than or equal to 70 millimeters. More preferably, the overall length of an aerosol-generating article according to the invention is preferably less than or equal to 60 millimeters. Even more preferably, the overall length of an aerosol-generating article according to the invention is preferably less than or equal to 50 millimeters. In some embodiments, the overall length of the aerosol-generating article is preferably from approximately 38 millimeters to approximately 70 millimeters, more preferably from approximately 40 millimeters to approximately 70 millimeters, and even more preferably from approximately 42 millimeters to approximately 70 millimeters. In other embodiments, the overall length of the aerosol-generating article is preferably from approximately 38 millimeters to approximately 60 millimeters, more preferably from approximately 40 millimeters to approximately 60 millimeters, and even more preferably from approximately 42 millimeters to approximately 60 millimeters.In other embodiments, the total length of the aerosol-generating article is preferably from approximately 38 millimeters to approximately 50 millimeters, more preferably from approximately 40 millimeters to approximately 50 millimeters, and still more preferably from approximately 42 millimeters to approximately 50 millimeters. In one illustrative embodiment, the total length of the aerosol-generating article is approximately 45 millimeters. The aerosol-generating article has an outer diameter of at least 5 millimeters. Preferably, the aerosol-generating article has an outer diameter of at least 6 millimeters. More preferably, the aerosol-generating article has an outer diameter of at least 7 millimeters. Preferably, the aerosol-generating article has an external diameter less than or equal to approximately 12 millimeters. More preferably, the aerosol-generating article has an external diameter less than or equal to approximately 10 millimeters. Even more preferably, the aerosol-generating article has an external diameter less than or equal to approximately 8 millimeters. In some embodiments, the aerosol-generating article has an external diameter of approximately 5 millimeters to approximately 12 millimeters, preferably approximately 6 millimeters to approximately 12 millimeters, with a greater preference of approximately 7 millimeters to approximately 12 millimeters. In other embodiments, the aerosol-generating article has an external diameter of approximately 5 millimeters to approximately 10 millimeters, preferably approximately 6 millimeters to approximately 10 millimeters, with a greater preference of approximately 7 millimeters to approximately 10 millimeters. In other embodiments, the aerosol-generating article has an external diameter of approximately 5 millimeters to approximately 8 millimeters, preferably approximately 6 millimeters to approximately 8 millimeters, with a greater preference of approximately 7 millimeters to approximately 8 millimeters. ocrmnn / oznz / R / vi The external diameter of the aerosol-generating article may be essentially constant along its entire length. Alternatively, different portions of the aerosol-generating article may have different external diameters. In particularly preferred embodiments, one or more of the components of the aerosol generating article are individually enclosed by their own wrapper. In one embodiment, the aerosol-generating substrate bar and the nozzle element are individually wrapped. The upstream element, the aerosol-generating substrate bar, and the hollow tubular element are combined with an outer wrapper. Subsequently, they are combined with the nozzle element, which has its own wrapper, by means of nozzle paper. Preferably, at least one of the components of the aerosol-generating article is wrapped in a hydrophobic wrapper. The term “hydrophobic” refers to a surface that exhibits water-repellent properties. A useful way to determine this is by measuring the water contact angle. The “water contact angle” is the angle, conventionally measured through the liquid, where a liquid / vapor interface meets a solid surface. It quantifies the wettability of a solid surface by a liquid using Young’s equation. Hydrophobicity, or water contact angle, is determined using the TAPPI T558 test method, and the result is presented as an interfacial contact angle, reported in degrees, and can range from near zero to nearly 180 degrees. In preferred embodiments, the hydrophobic wrapping includes a paper layer that has a water contact angle of approximately 30 degrees or more, and preferably approximately 35 degrees or more, or approximately 40 degrees or more, or approximately 45 degrees or more. For example, the paper layer may comprise PVOH (polyvinyl alcohol) or silicon. The PVOH may be applied to the paper layer as a surface coating, or the paper layer may comprise a surface treatment comprising PVOH or silicon. In a particularly preferred embodiment, an aerosol generating article according to the present invention comprises, in a linear sequential arrangement, an upstream element, an aerosol generating substrate bar located immediately downstream of the upstream element, a hollow tubular element located immediately downstream of the aerosol generating substrate bar, a nozzle element located immediately downstream of the aerosol cooling element, and one or more outer sheaths combining the upstream element, the aerosol generating substrate bar, the hollow tubular element, and the nozzle element. The upstream element defines an upstream section of the aerosol generating article. The hollow tubular element and the nozzle element form a downstream section of the aerosol generating article. The aerosol-generating substrate bar may be adjacent to the upstream element. The hollow tubular element may be adjacent to the aerosol-generating substrate bar. The nozzle element may be adjacent to the hollow tubular element. Preferably, the hollow tubular element is adjacent to the aerosol-generating substrate bar, and the nozzle element is adjacent to the hollow tubular element. The aerosol generating article has an essentially cylindrical shape and an external diameter of approximately 7.23 millimeters. The upstream element that defines the upstream section has a length of 5 millimeters, the aerosol generating element bar has a length of 12 millimeters, the hollow tubular element has a length of 21 millimeters, and the nozzle element has a length of 7 millimeters. Thus, the length of the downstream section is 28 mm, and the total length of the aerosol generating element is approximately 45 millimeters. Therefore, the combined length of the hollow tubular element and the nozzle element is 28 mm. The upstream element has the form of a hollow cellulose acetate tow plug wrapped in a rigid plug wrapper. The aerosol-generating substrate stick comprises at least one of the aerosol-generating substrate types described above, and preferably a shredded tobacco material. In a preferred embodiment, the aerosol-generating substrate stick comprises 150 milligrams of a shredded tobacco material comprising 13 percent to 18 percent by weight of glycerol. In more detail, the hollow tubular element is shaped like a cardboard tube and has an internal diameter of approximately 6.7 millimeters. Thus, the thickness of a peripheral wall of the hollow tubular element is approximately 0.25 millimeters. A ventilation zone is provided comprising a circumferential row of openings along the hollow tubular element at 12 millimeters from an upstream end of the hollow tubular element and 29 millimeters from an upstream end of the upstream element (or upstream end of the aerosol generating article). The nozzle is shaped like a segment of low-density cellulose acetate filter. As discussed above, this description also refers to an aerosol generating system comprising an aerosol generating device having a distal end and a mouth-side end. The aerosol generating device may comprise a body. The body or housing of the aerosol generating device may define a device cavity for detachably receiving the aerosol generating article at the mouth-side end of the device. The aerosol generating device may comprise a heating element or heater for heating the aerosol generating substrate when the aerosol generating article is received within the device cavity. The device cavity may be referred to as the heating chamber of the aerosol-generating device. The device cavity may extend from a distal end to a mouth-side, or proximal, end. The distal end of the device cavity may be a closed end, and the mouth-side, or proximal, end may be an open end. An aerosol-generating item may be inserted into the device cavity, or heating chamber, through the open end of the cavity. The device cavity may be cylindrical to accommodate the shape of an aerosol-generating item. The expression “received within” can refer to the fact that a component or element is received wholly or partially within another component or element. For example, the expression “the aerosol-generating article is received within the device cavity” refers to the aerosol-generating article being received wholly or partially within the device cavity of the aerosol-generating article. When the aerosol-generating article is received within the device cavity, it may be adjacent to the distal end of the cavity. The distal end of the device cavity may be defined by an end wall. The length of the device cavity can be between approximately 10 mm and approximately 50 mm. The length of the device cavity can be between approximately 20 mm and approximately 40 mm. The length of the device cavity can be between approximately 25 mm and approximately 30 mm. The length of the device cavity (or heating chamber) may be equal to or greater than the length of the aerosol-generating substrate bar. The length of the device cavity may be equal to or greater than the combined length of the upstream section or element and the aerosol-generating substrate bar. The length of the device cavity may be such that the downstream section, or a portion thereof, is configured to protrude from the device cavity when the aerosol-generating article is received within the device cavity. The length of the device cavity may be such that a portion of the downstream section (such as the hollow tubular element or nozzle element) is configured to protrude from the device cavity when the aerosol-generating article is received within the device cavity.The length of the device cavity may be such that a portion of the downstream section (such as the hollow tubular element or nozzle element) is configured to be received within the device cavity when the aerosol-generating article is received within the device cavity. At least 25 percent of the downstream section length may be inserted or received within the device cavity when the aerosol-generating article is received within the device. At least 30 percent of the downstream section length may be inserted or received within the device cavity when the aerosol-generating article is received within the device. At least 30 percent of the length of the hollow tubular element may be inserted into or received within the device cavity when the aerosol-generating article is received within the device. At least 40 percent of the length of the hollow tubular element may be inserted into or received within the device cavity when the aerosol-generating article is received within the device. At least 50 percent of the length of the hollow tubular element may be inserted into or received within the device cavity when the aerosol-generating article is received within the device. Various lengths of the hollow tubular element are described in more detail within this description. Optimizing the quantity or length of the item inserted into the aerosol generating device can improve the item's resistance to inadvertently falling out during use. Specifically, during heating of the aerosol generating substrate, the substrate may shrink, reducing its external diameter and thus lessening the extent to which the inserted portion of the item can frictionally engage with the device cavity. The inserted portion of the item, or the portion of the item designed to fit within the device cavity, may be the same length as the device cavity itself. ocrmnn / oznz / R / vi Preferably, the length of the device cavity is between approximately 25 mm and approximately 29 mm. More preferably, the length of the device cavity is between approximately 26 mm and approximately 29 mm. Even more preferably, the length of the device cavity is approximately 27 mm or approximately 28 mm. Preferably, the combined length of the upstream section (or element) and the inserted portion of the downstream section or hollow tubular element is equivalent to between approximately 80 percent and approximately 120 percent of the length of the protruding portion of the aerosol-generating article.The inserted portion of the downstream section, hollow tubular element, or aerosol-generating article refers to the portion of the downstream section, hollow tubular element, or aerosol-generating article that is configured to be positioned within the device cavity when the aerosol-generating article is received therein. The protruding portion of the aerosol-generating article refers to the article that is configured to be positioned outside the device cavity, or protrude from the device, when the aerosol-generating article is received therein. The inventors have found that this relationship minimizes the risk of accidental displacement of the article from the device during use, particularly after possible shrinkage of the article during use.The portion of the aerosol-generating article configured to be inserted into the device is preferably longer than the portion of the aerosol-generating article configured to protrude from the device, when the aerosol-generating article is received inside the aerosol-generating device. The diameter of the device cavity can be between approximately 4 mm and approximately 10 mm. The diameter of the device cavity can be between approximately 5 mm and approximately 9 mm. The diameter of the device cavity can be between approximately 6 mm and approximately 8 mm. The diameter of the device cavity can be between approximately 7 mm and approximately 8 mm. The diameter of the device cavity can be between approximately 7 mm and approximately 7.5 mm. The diameter of the device cavity can be essentially equal to or larger than the diameter of the aerosol-generating item. Alternatively, the device cavity diameter can be the same as the aerosol-generating item's diameter to ensure a tight fit. The device cavity may be configured to establish a tight fit with an aerosol-generating article received within the device cavity. A tight fit may refer to a snug fit. The aerosol-generating device may comprise a peripheral wall. Such a peripheral wall may define the device cavity, or heating chamber. The peripheral wall defining the device cavity may be configured to mate with an aerosol-generating article received within the device cavity in a tight-fitting manner, such that there is essentially no gap or void between the peripheral wall defining the device cavity and the aerosol-generating article when it is received within the device. Such a tight fit can establish an airtight seal or configuration between the device cavity and an aerosol-generating item received therein. With such an airtight configuration, there would essentially be no empty space or gap between the peripheral wall that defines the device cavity and the aerosol-generating item for air to flow through. The airtight fit with an aerosol-generating article can be set along the entire length of the device cavity or along a portion of the length of the device cavity. The aerosol-generating device may include an airflow channel extending between a channel inlet and a channel outlet. This airflow channel may be configured to establish continuous communication between the interior of the device cavity and the exterior of the aerosol-generating device. The airflow channel of the aerosol-generating device may be defined within the device housing to allow continuous communication between the interior of the device cavity and the exterior of the aerosol-generating device. When an aerosol-generating item is received within the device cavity, the airflow channel may be configured to provide airflow within the item to deliver generated aerosol to a user who inhales from the mouth end of the item. The airflow channel of the aerosol-generating device can be defined within, or by, the peripheral wall of the aerosol-generating device housing. In other words, the airflow channel of the aerosol-generating device can be defined within the thickness of the peripheral wall, by the inner surface of the peripheral wall, or a combination of both. The airflow channel can be partially defined by the inner surface of the peripheral wall and partially defined within the thickness of the peripheral wall. The inner surface of the peripheral wall defines a peripheral boundary of the device cavity. ocnt?nn / C7n7 / e / Yi The airflow channel of the aerosol-generating device may extend from an inlet located at the mouth-side, or proximal, end of the aerosol-generating device to an outlet located away from the mouth-side end of the device. The airflow channel may extend along a direction parallel to the longitudinal axis of the aerosol-generating device. The heater can be any suitable type of heater. Preferably, in the present invention, the heater is an external heater. Preferably, the heater can externally heat the aerosol-generating item as it is received within the aerosol-generating device. Such an external heater can surround the aerosol-generating item as it is inserted into or received within the aerosol-generating device. In some embodiments, the heater is arranged to heat the external surface of the aerosol-generating substrate. In other embodiments, the heater is arranged to be inserted into an aerosol-generating substrate when the substrate is received within the cavity. The heater may be placed inside the heating device cavity or chamber. The heater may comprise at least one heating element. The at least one heating element may be any suitable type of heating element. In some embodiments, the device comprises only one heating element. In some embodiments, the device comprises a plurality of heating elements. The heater may comprise at least one resistive heating element. Preferably, the heater comprises a plurality of resistive heating elements. Preferably, the resistive heating elements are electrically connected in a parallel arrangement. Advantageously, providing a plurality of resistive heating elements electrically connected in a parallel arrangement can facilitate the supply of the desired electrical power to the heater while reducing or minimizing the voltage required to supply the desired electrical power.Advantageously, reducing or minimizing the voltage required to operate the heater can make it easier to reduce or minimize the physical size of the power supply. Suitable materials for forming at least one resistive heating element include, but are not limited to: semiconductors such as doped ceramics, electrically conductive ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys, and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals.Examples of suitable metal alloys include stainless steel, nickel, cobalt, chromium, aluminum, titanium, zirconium, hafnium, niobium, molybdenum, tantalum, tungsten, tin, gallium, manganese, and iron containing nickel-based alloys and superalloys, iron, cobalt, stainless steel, Timetal®, and iron, manganese, and aluminum-based alloys. In some embodiments, the at least one resistive heating element comprises one or more stamped portions of electrically resistive material, such as stainless steel. Alternatively, the at least one resistive heating element may comprise a heating filament or wire, for example, a wire of Ni-Cr (Nickel-Chromium), platinum, tungsten, or alloy. In some embodiments, the at least one heating element comprises an electrical insulation substrate, wherein at least one resistive heating element is provided on the electrical insulation substrate. The electrical insulation substrate may comprise any suitable material. For example, the electrical insulation substrate may comprise one or more of the following: paper, glass, ceramic, anodized metal, coated metal, and polyimide. The ceramic may comprise mica, alumina (Al₂O₃), or zirconia (ZrO₂). Preferably, the electrical insulation substrate has a thermal conductivity less than or equal to approximately 40 watts per meter Kelvin, preferably less than or equal to approximately 20 watts per meter Kelvin, and ideally less than or equal to approximately 2 watts per meter Kelvin. The heater may comprise a heating element consisting of a rigid electrical insulation substrate with one or more electrically conductive tracks or wire disposed on its surface. The size and shape of the electrical insulation substrate may allow it to be inserted directly into an aerosol-generating substrate. If the electrical insulation substrate is not sufficiently rigid, the heating element may include additional reinforcing means. A current may be passed through one or more electrically conductive tracks to heat the heating element and the aerosol-generating substrate. In some embodiments, the heater comprises an inductive heating arrangement. The inductive heating arrangement may comprise an inductor coil and a power supply configured to provide a high-frequency oscillating current to the inductor coil. As used herein, a high-frequency oscillating current means an oscillating current having a frequency between approximately 500 kHz and approximately 30 MHz. The heater may advantageously comprise a DC / AC inverter for converting a DC current supplied by a DC power supply into alternating current. The inductor coil may be arranged to generate a high-frequency oscillating electromagnetic field upon receiving a high-frequency oscillating current from the power supply. The inductor coil may be arranged to generate a high-frequency oscillating electromagnetic field within the cavity of the device.In some embodiments, the inductor coil may essentially enclose the device cavity. The inductor coil may extend at least partially along the length of the device cavity. The heater may comprise an inductive heating element. The inductive heating element may be a susceptor element. As used herein, the term susceptor element refers to an element comprising a material capable of converting electromagnetic energy into heat. When a susceptor element is placed in an alternating electromagnetic field, the susceptor heats up. The heating of the susceptor element may result from at least one of the hysteresis losses and eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material. A susceptor element may be arranged such that, when the aerosol-generating article is received into the cavity of the aerosol-generating device, the oscillating electromagnetic field generated by the inductor coil induces a current in the susceptor element, causing it to heat up. In these embodiments, the aerosol-generating device is preferably capable of generating a fluctuating electromagnetic field having a magnetic field strength (field strength H) of between 1 and 5 kiloamperes per meter (kA-m), preferably between 2 and 3 kA / m, for example, approximately 2.5 kA / m. The electrically operated aerosol-generating device is preferably capable of generating a fluctuating electromagnetic field having a frequency of between 1 and 30 MHz, for example, between 1 and 10 MHz, or between 5 and 7 MHz. In these embodiments, the susceptor element is preferably located in contact with the aerosol-forming substrate. In some embodiments, a susceptor element is located in the aerosol-generating device. In these embodiments, the susceptor element may be located in the cavity. The aerosol-generating device may comprise only one susceptor element. The aerosol-generating device may comprise a plurality of susceptor elements. In some embodiments, the susceptor element is preferably arranged to heat the external surface of the aerosol-forming substrate. The susceptor element may comprise any suitable material. The susceptor element may be formed from any material that can be induction heated to a temperature sufficient to release volatile compounds from the aerosol-forming substrate. Suitable materials for the elongated susceptor element include graphite, molybdenum, silicon carbide, stainless steels, niobium, aluminum, nickel, nickel-containing compounds, titanium, and compounds of metallic materials. Some susceptor elements comprise a metal or carbon. Advantageously, the susceptor element may comprise or consist of a ferromagnetic material, for example, ferritic iron, a ferromagnetic alloy such as ferromagnetic steel or stainless steel, ferromagnetic particles, and ferrite. A suitable susceptor element may be made of, or comprise, aluminum.The susceptor element preferably comprises more than approximately 5 percent, preferably more than approximately 20 percent, and more preferably more than approximately 50 percent or more than approximately 90 percent of ferromagnetic or paramagnetic materials. Some elongated susceptor elements can be heated to a temperature exceeding approximately 250 degrees Celsius. The susceptor element may comprise a non-metallic core with a metallic layer disposed on the non-metallic core. For example, the susceptor element may comprise metallic tracks formed on an external surface of a ceramic core or substrate. In some embodiments, the aerosol generating device may comprise at least one resistive heating element and at least one inductive heating element. In some embodiments, the aerosol generating device may comprise a combination of resistive heating elements and inductive heating elements. During use, the heater can be controlled to operate within a defined temperature range, below a maximum operating temperature. An operating temperature range of approximately 150°C to approximately 300°C is preferred in the heating chamber (or device cavity). The heater's operating temperature range can be between approximately 150°C and approximately 250°C. ocnt?nn / C7n7 / e / Yi Preferably, the operating temperature range of the heater may be between approximately 150 degrees Celsius and approximately 200 degrees Celsius. More preferably, the operating temperature range of the heater may be between approximately 180 degrees Celsius and approximately 200 degrees Celsius. In particular, it has been found that optimal and consistent aerosol delivery can be achieved when using an aerosol generating device with an external heater having an operating temperature range between approximately 180 degrees Celsius and approximately 200 degrees Celsius, with aerosol generating items having a relatively low RTD (e.g., with a downstream RTD cross-section of less than 15 mm H2O), as mentioned in this description. In embodiments where the aerosol-generating article comprises a vent zone located along the downstream section or hollow tubular element, the vent zone may be arranged to be exposed when the aerosol-generating article is received within the device cavity. Therefore, the length of the device cavity or heating chamber may be less than the distance from the upstream end of the aerosol-generating article to a vent zone located along the downstream section. In other words, when the aerosol-generating article is received within the aerosol-generating device, the distance between the vent zone and the upstream end of the upstream element may be greater than the length of the heating chamber. When the item is received inside the device cavity, the vent area may be located at least 0.5 mm away (downstream of the item) from the mouth-side end (or mouth-side end face) of the device cavity or the device itself. When the item is received inside the device cavity, the vent area may be located at least 1 mm away (downstream of the item) from the mouth-side end (or mouth-side end face) of the device cavity or the device itself. When the item is received inside the device cavity, the vent area may be located at least 2 mm away (downstream of the item) from the mouth-side end (or mouth-side end face) of the device cavity or the device itself. Preferably, the ratio between the distance between the ventilation zone and the upstream end of the upstream element and the length of the heating chamber is approximately 1.03 to approximately 1.13. This positioning of the vent zone ensures that the vent zone is not occluded within the cavity of the device itself, while minimizing the risk of occlusion by a user's lips or hands, as the vent zone is located in the most upstream position of the downstream end of the article as reasonably possible without being occluded within the cavity of the device. The aerosol-generating device may include a power supply. The power supply may be a DC power supply. In some embodiments, the power supply is a battery. The power supply may be a nickel-metal hydride battery, a nickel-cadmium battery, or a lithium-based battery, for example, a lithium-cobalt, lithium-iron-phosphate, or lithium-polymer battery. However, in some embodiments, the power supply may be another form of charge storage device, such as a capacitor. The power supply may require recharging and may have a capacity that allows for the storage of sufficient energy for one or more user operations, for example, one or more aerosol-generating experiences.For example, the power supply may have sufficient capacity to allow continuous heating of an aerosol-generating substrate for a period of approximately six minutes, which corresponds to the typical time it takes to smoke a conventional cigarette, or for a period that is a multiple of six minutes. In another example, the power supply may have sufficient capacity to allow a predetermined number of puffs or discrete activations of the heater. The following is a non-exhaustive list of non-limiting examples. One or more of the features in these examples may be combined with one or more features of another example, modality, or aspect described herein. EJ1. An aerosol generating article comprising: an aerosol generating substrate bar; and a downstream section disposed downstream of the aerosol generating substrate bar, the downstream section comprising at least one hollow tubular element. EJ2. An aerosol generating article according to example EJ1, further comprising an upstream section provided upstream of the aerosol generating substrate bar, the upstream section comprising at least one upstream element. EJ3. An aerosol generating article in accordance with example EJ2, wherein the upstream element has a length of between 2 millimeters and 8 millimeters. ocnt?nn / C7n7 / e / Yi EJ4. An aerosol generating article in accordance with example EJ2 or EJ3, wherein the upstream element is formed by a hollow tubular segment defining a longitudinal cavity that provides an unrestricted flow channel. EJ5. An aerosol generating article in accordance with example EJ4, wherein the longitudinal cavity of the hollow tubular segment has a diameter of at least 5 millimeters. EJ6. An aerosol generating article in accordance with Example EJ4 or EJ5, wherein the hollow tubular segment has a wall thickness of less than 1 millimeter. EJ7. An aerosol generating article in accordance with any of Examples EJ2 to EJ6, wherein the upstream element has a suction resistance (RTD) of less than 2 mm H2O. EJ8. An aerosol generating article in accordance with any of Examples EJ2 to EJ7, wherein an upstream end of the upstream element defines an upstream end of the aerosol generating article. EJ9. An aerosol generating article in accordance with any of the foregoing examples, further comprising a ventilation zone. EJ10. An aerosol generating article in accordance with Example EX9, wherein the venting zone is provided at a location along the hollow tubular element of the downstream section. EJ11. An aerosol generating article in accordance with Example EJ9 or EJ10, wherein the ventilation zone is provided at a distance of between 26 millimeters and 33 millimeters from the upstream end of the article. EJ12. An aerosol generating article in accordance with Example EJ9 or EJ10, wherein the ventilation zone is provided at a distance of between 27 millimeters and 31 millimeters from the upstream end of the article. EP3. An aerosol generating article in accordance with any of Examples EJ9 to EJ12, wherein the ventilation zone is provided at a distance of between 12 millimeters and 20 millimeters from the downstream end of the article. EJ14. An aerosol generating article in accordance with any of Examples EJ9 to EJ13, wherein the venting zone is provided at least 10 millimeters downstream of the downstream end of the aerosol generating substrate bar. ocrmnn / cznz / R / vi EJ15. An aerosol generating article in accordance with any of the foregoing examples, wherein the hollow tubular element of the downstream section has a length of between 17 millimeters and 25 millimeters. EJ16. An aerosol generating article in accordance with any of the foregoing examples, wherein the hollow tubular element of the downstream section has an internal volume of at least 300 cubic millimeters. EJ17. An aerosol generating article in accordance with any of the above examples, wherein the aerosol generating substrate rod has a length of between 8 millimeters and 16 millimeters. EJ18. An aerosol generating article in accordance with any of the above examples, wherein the aerosol generating substrate rod has a resistance to suction (RTD) of between 4 mmHiO and 10 mm H2O. EP9. An aerosol generating article in accordance with any of the foregoing examples, wherein the aerosol generating substrate comprises a shredded tobacco material. EJ20. An aerosol-generating article in accordance with Example EJ19, wherein the shredded tobacco material has an average density of between 150 milligrams per cubic centimeter and 500 milligrams per cubic centimeter. EJ21. An aerosol-generating article in accordance with any of the foregoing examples, wherein the aerosol-generating substrate comprises one or more aerosol formers and wherein the aerosol former content in the aerosol-generating substrate is between 10 percent and 20 percent by weight, on a dry weight basis. EJ22. An aerosol generating article according to Example EJ19, wherein the aerosol former comprises one or more glycerin and propylene glycol. EJ23. An aerosol generating article in accordance with any of the foregoing examples, wherein the aerosol generating substrate comprises tobacco scraps. EJ24. An aerosol generating article in accordance with any of the foregoing examples, wherein the downstream section further comprises a nozzle element. EJ25. An aerosol generating article according to Example EJ24, wherein the nozzle element comprises at least one nozzle filter segment formed from a fibrous filter material. EJ26. An aerosol generating article in accordance with Example EJ24 or EJ25, wherein the length of the nozzle element is between 3 millimeters and 11 millimeters. ocnt?nn / C7n7 / e / Yi EJ27. An aerosol generating article in accordance with any of Examples EJ24 to EJ26, wherein the nozzle element has a suction resistance (RTD) of between 4 mmHiO and 11 mmHiO. EJ28. An aerosol generating article in accordance with any of Examples EJ24 to EJ27, wherein the combined length of the hollow tubular element and the nozzle element of the downstream section is between 24 millimeters and 32 millimeters. EJ29. An aerosol generating article in accordance with any of the foregoing examples, wherein the resistance to suction (RTD) of the article is between 20 mm H2O and 22 mm H2O. EJ30. An aerosol generating article in accordance with any of the foregoing examples, wherein the outside diameter of the article is essentially uniform along its length. EJ31. An aerosol-generating article in accordance with any of the foregoing examples, wherein the ventilation level of the aerosol-generating article is from 10 percent to 30 percent. EJ32. An aerosol-generating article in accordance with any of the foregoing examples, wherein a EJ33. An aerosol generating system comprising an aerosol generating article in accordance with any of the above examples and an aerosol generating device comprising a heating chamber for receiving the aerosol generating article and at least one heating element provided in or around the periphery of the heating chamber. The invention will now be further described with reference to the drawings in the accompanying Figures, where: Figure 1 shows a schematic side perspective view of an aerosol generating article according to one embodiment of the invention; Figure 2 shows a schematic side section view of the aerosol generating article according to one embodiment of the invention; and Figure 3 shows a schematic side section view of the aerosol generating system comprising an aerosol generating article according to an embodiment of the invention and an aerosol generating device. The aerosol-generating article 10 shown in Figure 1 comprises an aerosol-generating substrate bar 12 and a downstream section 14 located downstream of the aerosol-generating substrate bar 12. The aerosol-generating article 10 thus extends from an upstream or distal end 16—essentially coinciding with an upstream end of the bar 12—to a downstream or mouth-side end 18, coinciding with a downstream end of the downstream section 14. The downstream section 14 comprises a hollow tubular element 20 and a nozzle element 50. The aerosol generator item 10 has a total length of approximately 45 millimeters and an external diameter of approximately 7.2 mm. The aerosol-generating substrate stick 12 comprises a shredded tobacco material. The aerosol-generating substrate stick 12 comprises 150 milligrams of a shredded tobacco material comprising 13 to 16 percent by weight of glycerin. The density of the aerosol-generating substrate is approximately 300 mg per cubic centimeter. The RTD of the aerosol-generating substrate stick 12 is between approximately 6 and 8 mm H2O. The aerosol-generating substrate stick 12 is individually wrapped by a cap wrapper (not shown). The cap wrapper (not shown) enclosing the aerosol-generating substrate stick comprises a non-porous paper having a basis weight of approximately 25 grams per square meter (g / m2) and a thickness of approximately 40 micrometers. The hollow tubular element 20 is located immediately downstream of the aerosol generating substrate bar 12; the hollow tubular element 20 is aligned longitudinally with the bar 12. The upstream end of the hollow tubular element 20 abuts the downstream end of the aerosol generating substrate bar 12. The hollow tubular element 20 defines a hollow section of the aerosol-generating article 10. The hollow tubular element does not substantially contribute to the overall RTD of the aerosol-generating article. In more detail, the RTD of the hollow tubular element 20 is approximately 0 mm H2O. As shown in Figure 2, the hollow tubular element 20 is provided in the form of a hollow cylindrical tube made of cardboard. The hollow tubular element 20 defines an internal cavity 22 that extends from an upstream end of the hollow tubular element 20 to a downstream end of the hollow tubular element 20. The internal cavity 22 is essentially empty, and therefore, essentially unrestricted airflow is permitted along the internal cavity 22. The hollow tubular element 20 does not essentially contribute to the overall RTD of the aerosol-generating article 10. The hollow tubular element 20 has a length of approximately 21 millimeters, an outer diameter of approximately 7.2 millimeters, and an inner diameter of approximately 6.7 millimeters. Thus, the thickness of a peripheral wall of the hollow tubular element 20 is approximately 0.25 millimeters. The aerosol-generating article 10 comprises a vent zone 30 disposed at a location along the hollow tubular element 20. More specifically, the vent zone 30 is provided approximately 16 mm from the downstream end 18 of article 10. The vent zone 30 is provided approximately 12 mm downstream from the downstream end of the bar 12 of the aerosol-generating substrate. The vent zone 30 is provided approximately 9 mm upstream from the upstream end of the nozzle element 50. The vent zone 30 comprises a circumferential row of openings or perforations that circumscribe the hollow tubular element 20. The perforations of the vent zone 30 extend through the wall of the hollow tubular element 20 to allow fluid to enter the internal cavity 22 from outside article 10.The ventilation level of aerosol generating item 10 is approximately 16 percent. On an aerosol-generating substrate bar 12 and a downstream section 14 at a location downstream of bar 12, the aerosol-generating article 100 comprises an upstream section 40 at a location upstream of bar 12. As such, the aerosol-generating article 100 extends from a distal end 16 that essentially coincides with an upstream end of the upstream section 40 to a mouth-side or downstream end 18 that essentially coincides with a downstream end of the downstream section 14. The upstream section 40 comprises an upstream element 42 located immediately upstream of the aerosol-generating substrate bar 12. The upstream element 42 is longitudinally aligned with the bar 12. The downstream end of the upstream element 42 abuts the upstream end of the aerosol-generating substrate bar 12. The upstream element 42 is provided in the form of a hollow cylindrical plug of cellulose acetate tow having a wall thickness of approximately 1 mm and defining an internal cavity 23. The upstream element 42 has a length of approximately 5 mm. An external diameter of the upstream element 42 is approximately 7.1 mm. An internal diameter of the upstream element 42 is approximately 5.1 mm. Nozzle element 50 extends from the downstream end of the hollow tubular element 20 to the downstream or mouth end of the aerosol generating article 10. Nozzle element 50 is approximately 7 mm long. The outside diameter of nozzle element 50 is approximately 7.2 mm. Nozzle element 50 comprises a low-density cellulose acetate filter segment. The RTD of nozzle element 50 is approximately 8 mm H2O. Nozzle element 50 can be individually wrapped by a cap wrapper (not shown). As shown in Figures 1 and 2, Article 10 comprises an upstream enclosure 44 that circumscribes the upstream element 42, the aerosol-generating substrate 12, and the hollow tubular element 20. The vent zone 30 may also comprise a circumferential row of perforations provided in the upstream enclosure 44. The perforations in the upstream enclosure 44 overlap the perforations provided in the hollow tubular element 20. Accordingly, the upstream enclosure 44 covers the perforations of the vent zone 30 provided in the hollow tubular element 20. Article 10 further comprises a tip wrap 52 that encloses the hollow tubular element 20 and the nozzle element 50. The tip wrap 52 covers the portion of the upstream wrap 44 that covers the hollow tubular element 20. In this way, the tip wrap 52 effectively connects the nozzle element 50 to the other components of Article 10. The width of the tip wrap 52 is approximately 26 mm. In addition, the ventilation zone 30 may comprise a circumferential row of perforations provided in the tip wrap 52. The perforations in the tip wrap 52 overlap the perforations provided in the hollow tubular element 20 and the upstream wrap 44. Consequently, the tip wrap 52 covers the perforations of the ventilation zone 30 provided in the hollow tubular element 20 and the upstream wrap 44. Figure 3 illustrates an aerosol generating system 100 comprising an illustrative aerosol generating device 1 and the aerosol generating article 10, equivalent to that shown in Figures 1 and 2. Figure 3 illustrates a mouth-side end portion downstream of the aerosol generating device 1 where the device cavity is defined and the aerosol generating article 10 can be received. The aerosol generating device 1 comprises a housing (or body) 4, extending between a mouth-side end 2 and a distal end (not shown). The housing 4 comprises a peripheral wall 6. The peripheral wall 6 defines a device cavity for receiving an aerosol generating article 10. The device cavity is defined by a closed distal end and an open mouth-side end.The mouth-side end of the device cavity is located at the mouth-side end of the aerosol generating device 1. The aerosol generating item 10 is configured to be received through the mouth-side end of the device cavity and is configured to abut a closed end of the device cavity. An airflow channel of the device 5 is defined within the peripheral wall 6. The airflow channel 5 extends between an inlet 7 located at the mouth end of the aerosol-generating device 1 and the closed end of the device cavity. Air can enter the aerosol-generating substrate 12 through an opening (not shown) provided at the closed end of the device cavity, ensuring continuous communication between the airflow channel 5 and the aerosol-generating substrate 12. The aerosol generating device 1 further comprises a heater (not shown) and a power source (not shown) for supplying power to the heater. A controller (not shown) is also provided for controlling the power supply to the heater. The heater is configured to heat the aerosol generating article 10 in a controlled manner during use, when the aerosol generating article 1 is received into the device 1. The heater is preferably arranged to externally heat the aerosol generating substrate 12 for optimal aerosol generation. The ventilation zone 30 is arranged to be exposed when the aerosol generating article 10 is received into the aerosol generating device 1. In the embodiment shown in Figure 3, the cavity of the device defined by the peripheral wall 6 is 28 mm long.When item 10 is received into the device cavity, the upstream section 40, the aerosol-generating substrate bar 12, and an upstream portion of the hollow tubular element 20 are received into the device cavity. This upstream portion of the hollow tubular element 20 is 11 mm long. Consequently, approximately 28 mm of item 10 is received into device 1, and approximately 17 mm of item 10 is located outside of device 1. In other words, approximately 17 mm of item 10 protrudes from device 1 when item 10 is received into it. This length PL of item 10 protruding from device 1 is shown in Figure 3. As a result, the vent zone 30 is advantageously located outside device 1 when article 10 is inserted into device 1. When the device cavity is 28 mm long, the vent zone 30 is located 1 mm downstream of the end on the side of the mouth 2 of device 1 when article 10 is received inside device 1. For the purposes of this description and the appended claims, unless otherwise stated, all numbers expressing quantities, percentages, etc., are to be understood as modified in all cases by the term approximately. Furthermore, all intervals include the maximum and minimum points described and include any intermediate intervals therein, which may or may not be specifically listed in this description. In this context, therefore, a number A is understood to be A ± 10% of A.Within this context, a number A may be considered to include numerical values ​​that are within the general standard error for the measurement of the property that modifies the number A. The number A, in some cases as used in the appended claims, may deviate by the percentages listed above, provided that the amount by which A deviates does not materially affect the basic and novel feature(s) of the claimed invention. Furthermore, all intervals include the maximum and minimum points described and include any intermediate intervals therein, which may or may not be specifically listed in this description.

Claims

1. An aerosol generating article comprising: an aerosol generating substrate bar having a length of between 8 mm and 16 mm; an upstream element provided upstream of the aerosol generating substrate bar, the upstream element having an outside diameter of between 6 mm and 8 mm; a nozzle element provided downstream of the aerosol generating substrate bar; and a hollow tubular element provided between the aerosol generating substrate bar and the nozzle element, wherein an internal volume defined by the hollow tubular element is at least 300 cubic millimeters; wherein a combined length of the hollow tubular element and the nozzle element is between 24 mm and 32 mm.

2. An aerosol generating article according to claim 1, wherein the upstream element has a length of between 2 mm and 8 mm.

3. An aerosol generating article according to any of the preceding claims, wherein the hollow tubular element is adjacent to the nozzle element.

4. An aerosol generating article according to any of the preceding claims, wherein the wall thickness of the hollow tubular element is at least 100 micrometers.

5. An aerosol generating article according to any of the preceding claims, wherein the wall thickness of the hollow tubular element is not greater than 2 mm.

6. An aerosol generating article according to any of the preceding claims, wherein the hollow tubular element consists of a continuous hollow tubular segment.

7. An aerosol generating article according to any of the preceding claims, wherein the length of the hollow tubular element is at least 15 mm.

8. An aerosol generating article according to any of the preceding claims, wherein the length of the hollow tubular element is between 17 mm and 25 mm.

9. An aerosol generating article according to any of the preceding claims, wherein the aerosol generating substrate comprises one or more aerosol formers and wherein the aerosol former content in the aerosol forming substrate is at least 10 percent by weight, on a dry weight basis.

10. An aerosol generating article according to any of the preceding claims, wherein the aerosol generating substrate comprises a shredded tobacco material.

11. An aerosol generating article according to claim 10, wherein the shredded tobacco material has a density of 150 milligrams per cubic centimeter to 500 milligrams per cubic centimeter.

12. An aerosol generating article according to any of the preceding claims, wherein the length of the nozzle element is between 3 mm and 11 mm.

13. An aerosol generating article according to any of the preceding claims, wherein the length of the aerosol generating substrate rod is between 10 mm and 14 mm.

14. An aerosol generating system comprising an aerosol generating article according to any preceding claim and an aerosol generating device comprising a heating chamber for receiving the aerosol generating article and at least one heating element provided in or around the periphery of the heating chamber.

15. An aerosol generating system according to claim 14, wherein, when the aerosol generating article is received within the aerosol generating device, at least 10 mm of the hollow tubular element is located within the heating chamber.