Aerosol sampling device

Abstract

The invention relates to an aerosol sampling device (1) comprising: - a duct (3); - a plurality of manifolds (5) in fluid communication with the duct, each manifold extending in a collection direction (A) and comprising a nozzle (7), a tube (9), a filter (10) configured to capture aerosols, and a neck (12) configured to allow a critical flow of fluid in the manifold, each tube having an inlet and an outlet and being rectilinear between the inlet and the outlet; and - a vacuum pump (14) fluidically connected to the manifolds via the duct.

Description

[0001] DESCRIPTION

[0002] TITLE: Aerosol Sampling Device

[0003] DOMAIN

[0004] The invention relates to aerosol sampling systems, in particular for measuring the homogeneity of aerosol concentration in a ventilation duct, especially supermicron aerosols.

[0005] STATE OF THE ART

[0006] Aerosols are solid or liquid particles of a substance or mixture of chemical substances suspended in a gaseous medium. Supermicron aerosols are aerosols with a size greater than or equal to one micron. Their size can reach 100 pm.

[0007] Aerosols are produced primarily in industrial settings. To monitor aerosol emissions, sensors can be installed in ducts, such as industrial exhaust vents or chimneys. These ducts typically have a dimension in a plane transverse to the flow direction that is greater than or equal to 30 cm.

[0008] To assess the homogeneity of aerosol concentration within a duct, various measurement methods exist, including one based on successive sampling within the duct by moving a measuring probe each time. This method measures local aerosol concentration at different locations but at different times.

[0009] Existing methods are unsatisfactory because they either rely on strong assumptions, such as the steady-state nature of aerosol flow and concentration over time, or they produce inaccurate measurements (due, for example, to the use of a sampling system with a bent section that causes aerosol loss). Therefore, there is a need for an aerosol measurement device capable of reliably and simultaneously measuring the concentration at different measurement points within a duct.

[0010] EXPOSED

[0011] One aim of this presentation is to propose an aerosol measurement device capable of reliably and simultaneously measuring the concentration at different measurement points in a flow duct, and in particular an industrial ventilation duct.

[0012] The goal is achieved through an aerosol sampling device comprising: a conduit, several collectors in fluidic communication with the conduit, each collector extending along a collection direction and comprising a nozzle, a tube, a filter configured to capture aerosols, a neck configured to allow critical fluid flow in the collector, each tube having an inlet and an outlet and being straight between the inlet and outlet, and a vacuum pump fidially connected to the collectors via the conduit.

[0013] Such a device is advantageously and optionally complemented by the following features, taken alone or in combination: the collectors are arranged parallel to each other and extend in the same collection direction, each collector comprising successively, in the collection direction, the nozzle, the tube, the filter, and the neck; the device includes, for each collector, a detachable fitting configured to connect or separate the collector and the conduit; all or part of the collectors each include an elbow fitting that fluidly connects the quick-connect fitting and the collector neck; and the conduit is formed of a plurality of sections that can be reversibly attached to each other, each section comprising a portion of a quick-connect fitting. The discussion also relates to an aerosol sampling system comprising a device such as has just been described.

[0014] Such a system is advantageously and optionally complemented by the following various features, taken alone or in combination: the flow duct comprises two outlets, each outlet being configured to receive a portion of the duct, the collectors being placed inside the flow duct so that the collection direction coincides with a principal flow direction of the duct; the system comprises two fixing pieces, each configured to fix a portion of the duct to one of the outlets, one of the fixing pieces being configured to prevent the rotation of the duct relative to the duct; one of the fixing pieces includes an angular reference for positioning the duct relative to the duct at a predetermined angular position around a principal extension direction of the duct; the duct is reversibly fixed to the duct;and the duct also includes an access hatch configured to allow insertion of the conduit and manifolds into the duct.

[0015] The presentation also relates to a process for collecting aerosols from a stream, the process comprising the following steps: arrangement in the stream of several collectors extending along a collecting direction, pressure reduction in a conduit, generation of a critical flow in each collector, each collector being fluidly connected to the conduit via a neck, isokinetic collection of aerosols from the stream into each collector through a nozzle, straight-line transport in each collector of the aerosols, and capture of the aerosols by a filter in each collector.Such a process is advantageously and optionally complemented by the following different features taken alone or in combination: a measurement of the quantity of aerosols captured by each filter and a measurement of the homogeneity of the aerosols in the flow based on the quantities of aerosols measured; the identification of an optimal measurement point corresponding to a position of the collector providing an optimal measurement of the quantity of aerosols captured, the optimal measurement having a minimum deviation from the other measurements of the quantity of aerosols captured.

[0016] The presentation finally focuses on a method of mounting an aerosol sampling device in a flow duct, as described so far, the method comprising the following steps:

[0017] - opening of two duct connections,

[0018] - opening of an inspection hatch in the duct,

[0019] - Insertion of the conduit into the duct through the access hatch,

[0020] - fixing a section of the conduit at each branch connection,

[0021] - Fluid connection of the conduit to the vacuum pump,

[0022] - Insertion of the collectors into the duct through the access hatch,

[0023] - fixing each collector to the duct, with the collection direction coinciding with the direction of fluid flow in the duct, and

[0024] - airtight closure of the inspection hatch and the connections.

[0025] DESCRIPTION OF THE FIGURES

[0026] Other features and advantages will become apparent from the following description, which is purely illustrative and not limiting, and should be read in conjunction with the accompanying drawings in which: Figure 1 and Figure 2 are schematic representations of an aerosol sampling device; Figure 3 is a schematic representation of a collector of an aerosol sampling device; Figure 4 is a schematic representation of an aerosol sampling system; Figure 5 is a schematic representation of an aerosol sampling method; and Figure 6 is a schematic representation of a method for assembling an aerosol sampling device.

[0027] DETAILED DESCRIPTION OF THE INVENTION

[0028] Aerosol sampling device

[0029] Referring to Figures 1 and 2, an aerosol sampling device 1 comprises a conduit 3. The conduit 3 can be straight, meaning it has an inlet and an outlet and extends in a straight line between the inlet and outlet. The conduit extends in a principal direction B. A principal direction of an object is understood here as the direction in which the object has its maximum dimension. Advantageously, the conduit 3 has a circular cross-section in a plane orthogonal to direction B. The conduit 3 can be formed from a plurality of sections 24 that can be joined together. The sections 24 can be joined reversibly, for example by threading, or conversely, the sections 24 can be welded together. The length of the conduit 24 can thus be adapted to the dimensions of the flow under study by adjusting the number of sections 24 of the conduit 3.

[0030] Device 1 comprises a plurality of collectors 5. Each collector 5 is arranged in a straight line from a nozzle 7 to a neck 12. The nozzle 7 corresponds to an inlet of the collector 5. Referring to Figure 3, each collector has a principal extension direction A, or "collection direction." The collection direction A is oriented from the nozzle 7 to the neck 12.

[0031] The nozzle 7 is located at one free end of a tube 9, which is contained within the collector 5. The tube 9 is straight: it has an inlet and an outlet and extends in a straight line between the inlet and outlet. The tube 9 is a profiled nozzle, beveled at the end. The beveled end of the tube 9 corresponds to the nozzle 7. The nozzle 7 reduces the flow disturbance at the nozzle, in the flow within which the collector is placed. The nozzle also optimizes the aerosol collection efficiency. The tube has a length along the collection direction A that is greater than or equal to 5 cm and less than or equal to 20 cm. This length is advantageously greater than or equal to ten times the diameter of the nozzle.

[0032] The collector 5 includes a filter 10 configured to capture aerosols. The filter

[0033] 10 is attached to tube 9. The collector advantageously includes a grid within it to hold the filter. Tube 9 is located between nozzle 7 and filter 10. The filters have a diameter in a plane orthogonal to the collection direction A that is less than or equal to 25 mm. This relatively small size limits the overall footprint of the collector 5 in a plane orthogonal to the collection direction A. This allows for an increased density of collectors in the device 1. It also prevents excessive obstruction of the flow in a duct, such as an industrial ventilation duct when the device is installed within a duct. Avoiding excessive obstruction of the flow in a duct prevents altering the flow properties.

[0034] 11. It is possible to associate different tubes with a filter, corresponding to different diameters. This makes it easier to achieve an isokinetic sampling regime. In device 1, all the collectors 5 advantageously have tubes and nozzles of the same dimensions.

[0035] The collector 5 includes a neck 12 which corresponds to a local reduction in the cross-section of the collector 5 in a plane orthogonal to the collection direction A. The neck 12 is fixed downstream of the filter 10, relative to the collection direction. The filter 10 is located between the tube 9 and the neck 12.

[0036] The reduction in cross-section is sufficient to allow critical fluid flow in the collector. This result can be achieved, in particular, by reducing the pressure on the downstream side of the neck relative to the collection direction A, i.e., on the side of the neck not connected to filter 10. The neck 12 can operate on the principle of critical orifices: as soon as the pressure difference between the upstream and downstream sides of the neck exceeds a predetermined threshold value associated with the neck, this ensures that the airflow through the neck remains constant regardless of the pressure differential between its upstream and downstream sides.

[0037] Each collector includes successively in the collection direction A the nozzle, the tube, the filter and the neck.

[0038] Each manifold 5 is fluidically connected to the conduit 3 in a detachable manner. This means that the inside of the manifold 5 is in communication with the inside of the conduit 3. In other words, a fluid can flow continuously from the inside of the manifold 5 into the inside of the conduit 3. The connection between the manifold 5 and the conduit 3 is sealed so that a fluid passing from the inside of the manifold 5 into the inside of the conduit 3 cannot leak outwards. The device includes a detachable fitting configured to connect or disconnect the manifold and the conduit.

[0039] The use of a detachable fitting between the manifold 5 and the conduit 3 limits the intrusion of the device 1 into a duct. This could be a ventilation duct, particularly an industrial ventilation duct. In the prior art, many aerosol sampling probes are bulky and cannot pass through conventional openings such as an access hatch. The detachable fitting allows the conduit and then the manifolds 5 to pass through, thus reducing the need to create openings in the duct specifically for aerosol measurements. The fitting can advantageously be a quick-connect fitting 16. A quick-connect fitting 16 allows two pressurized fluid lines to be joined. It comprises a male part 16A and a female part 16B that can be easily attached to or separated from each other, i.e., with one hand.A quick-connect fitting is also known by its English name. The manifold can be attached to one part of a fitting, either the male part 16A or the female part 16B, and the other part of the fitting, either the female part 16B or the male part 16A, is attached to the conduit 3.

[0040] The manifold 5 can be directly attached to the part of the fitting 16, i.e. the collar 12 is attached to the part of the fitting 16.

[0041] Alternatively, and with reference to Figure 2, the collector 5 may include an elbow fitting 18 located between the collar 12 and the quick-connect fitting 16. The elbow fitting 18 comprises an upstream arm 20 directly attached to the collar 12 and a downstream arm 22 directly attached to the quick-connect fitting 16. The upstream arm 20 is straight and has a principal extension direction oriented along the collection direction A. The downstream arm 22 is straight and has a principal extension direction not oriented along the collection direction A. For example, the downstream arm 22 is oriented, along a direction C, orthogonally to the collection direction A and to the principal extension direction B of the conduit 3. The downstream arm 22 is then directly attached to one part of the fitting 16, while the second part of the fitting is attached to the conduit 3.Device 1 may include two elbow fittings having the same upstream arm length but different downstream arm lengths. The upstream arm 20 and the downstream arm 22 may be removably attached to each other, for example, by threading. Alternatively, the upstream arm 20 and the downstream arm 22 may form a single piece, which may, for example, be obtained by bending a fluidic conduit channel. At least some of the sections 24 of the conduit 3 may include a portion of a quick-connect fitting. The sections may be arranged at different angular orientations so that the quick-connect fittings attached to two sections extend from the conduit 3 in different directions. The collectors 5 of Device 1 may be arranged parallel to each other to define a single collection direction A. Preferably, the nozzles are positioned in the same plane orthogonal to the collection direction A.When using manifolds without elbow fittings, the nozzles will be aligned parallel to the main extension direction B of the duct 3. When using manifolds with and without elbow fittings, the nozzles will be distributed in a plane orthogonal to the collection direction A. In this option, if the elbow fittings all have the same downstream arm length, the nozzles will be distributed in the plane along a maximum of three axes parallel to the main extension direction B of the duct 3. Also in this option, and if the elbow fittings have a variable downstream arm length, the nozzles can be distributed in the plane along more than three axes.

[0042] The use of elbow fittings allows a wider choice in the positions of the measurement points, i.e. the collector nozzles.

[0043] A support bar can be used to keep the manifolds parallel to each other.

[0044] Finally, device 1 includes a vacuum pump 14 fluidly connected to the manifolds 5 via conduit 3. The vacuum pump 14 is connected to one end of conduit 3. The other end of conduit 3 is hermetically sealed.

[0045] The pump is sized according to the number of collectors, the material of the filters used (paper or polypropylene for example) and the diameter of the collectors and the conduit.

[0046] There is thus a fluidic connection between the pump, the conduit, the quick fittings when present, then for each manifold 5, the neck 12, the filter 10, the tube 9 and finally the nozzle 7.

[0047] Aerosol sampling system

[0048] With reference to Figure 4, an aerosol sampling system 26 comprises a sampling device 1 as described so far. A system 26 includes a flow duct 27, the conduit 3 of the device 1 being attached to the flow duct. The flow duct has a principal flow direction E corresponding to the direction of fluid flow through the duct when the duct is used to transport a fluid.

[0049] In a plane orthogonal to direction E, the sheath can have a circular, square, or rectangular cross-section.

[0050] Advantageously, direction B of conduit 3 is orthogonal to direction E.

[0051] The collectors 5 are advantageously placed inside the duct so that the collection direction A coincides with the main flow direction E of the duct.

[0052] The duct 27 may include two branches 30 and 31 which are each configured to receive a portion of the conduit 3. The branches are inspection chambers or openings in the wall of the duct 27 and which allow communication between the inside and outside of the duct 27.

[0053] For example, connections 30 and 31 are "pneuro-op" type fluid connection connections. This is a standardized type of connection used in pneumatic and vacuum systems, designed according to specifications established by the European Committee of Pneumatic Equipment Manufacturers (PNEUROP). The hose can, for example, be drilled with two holes, and each hole is then covered by a pneurop connection, defining a branch with a diameter chosen from standard sizes.

[0054] The diameter of these branches can be chosen to be large enough to allow the conduit 3 to pass through. The diameter of branch 30, 31 can also be chosen to be small enough to prevent the conduit 3 from passing through when the collectors 5 are mounted on the conduit 3.

[0055] The conduit 3 can thus be held to the duct 27 by two portions of the conduit which can be located at the two ends of the conduit. The axis B of the conduit 3 can be oriented horizontally, vertically, or in any direction orthogonal to the flow direction E. The branches 30 and 31 can be located opposite each other in the duct 27; for example, they are aligned with each other along the main extension direction B of the conduit 3.

[0056] The system 26 may further include fasteners 32 for attaching the conduit 3 to the drainage duct 27. For example, they may attach the portion of the conduit passing through a branch of the duct to that branch. The fasteners may include an inner wall fitted to the dimensions of the conduit 3 and an outer wall fitted to the branch 30. The outer wall of the fasteners may conform to standard "pneuro-type" dimensions. The fasteners may include gaskets and clamping rings to ensure a secure and watertight connection between the conduit 3 and the duct 27.

[0057] Conduit 3 is advantageously fixed reversibly to sheath 27. This is the case, for example, when using seals and clamping rings separate from the other system components. Such seals and rings also allow for a watertight seal at the branch connections, even in the absence of conduit. Simply place a seal and a plug against each branch connection and secure the assembly with a clamping ring.

[0058] Optionally, one of the fixing parts 32 may include an angular reference for placing the conduit 3 relative to the duct 27 at a predetermined angular position around a main direction B of conduit extension.

[0059] Optionally, one of the fixing pieces 32 can be used to prevent the duct 3 from rotating relative to the sheath 27, and in particular its rotation around the main extension direction B of the duct 3. For example, one of the pieces may have an inner wall intended to be in contact with the duct 3, this inner wall having a non-circular cross-section, for example, a square or hexagonal shape. This shape limits the rotation. Advantageously, the outer wall of the duct, intended to be in contact with the inner wall of the fixing piece, may have a non-circular cross-section corresponding to the shape of the inner wall.These options respectively ensure on the one hand that the correct angular position of the device 1 inside the duct 27 is ensured, and in particular that the collection direction A coincides with the main direction E of fluid flow in the duct, and on the other hand that the correct angular position of the device is maintained.

[0060] I inside the sheath 27 during the study.

[0061] The duct 27 may include an inspection hatch 28 configured to allow the introduction into the duct of the conduit 3 on one side and the collectors 5 on the other. In other words, it is possible to introduce into the duct 27 through the inspection hatch 28: the conduit 3 without the collectors 5; and the collectors 5 without the conduit 3.

[0062] It is common for a duct 27 to include one or more inspection hatches, so the described device does not require dismantling the duct to perform aerosol measurements. The straight conduit 3, on the one hand, and the manifolds 5, which are also straight, do not require a large inspection hatch to be inserted into the duct 27. The inspection hatch can advantageously have dimensions of 100 mm x 200 mm, which are small enough not to unduly disrupt the flow in the duct and large enough to allow an arm and a manifold 5 to pass through the inspection hatch.

[0063] Aerosol sampling method

[0064] A sampling device as presented so far allows for the implementation of a P process for sampling aerosols in a flow.

[0065] With reference to Figure 5, we will present a method for implementing this process.

[0066] In a first step S1, several collectors 5 extending along a collection direction are placed in the flow. Advantageously, all the collectors are placed parallel to each other and define a single collection direction A. This collection direction advantageously corresponds to the principal flow direction E. In a second step S2, the pressure in the conduit 3 is reduced. For example, the vacuum pump 14, fluidly connected to the conduit 3, is activated. One end of the conduit 3 is fluidly connected to the vacuum pump 14, while the other end is hermetically sealed.

[0067] In a third step S3, a critical flow is generated in each collector 5, each collector being fluidly connected to the conduit 3 via the neck 12. The critical flow is obtained when the pressure difference between the upstream and downstream of the neck is greater than a predetermined threshold value.

[0068] In a fourth step S4, aerosols are isokinetically drawn from the flow in each collector through nozzle 7. The nozzle and tube diameters are adjusted to meet the isokinetic requirement. Prior to implementing process P, the operator can, depending on the average flow velocity, adjust the nozzle and tube diameters to meet the isokinetic requirement.

[0069] In a fifth step S5, aerosols are transported in a straight line into each collector. This transport takes place inside the straight tube 9 from its inlet, i.e. the nozzle 7, to its outlet located upstream of the filter 10. The straight nature of the tube between the nozzle and the filter helps to limit the deposition of aerosols, in particular supermicron aerosols, in the collector 5 before they are captured by the filter.

[0070] During a sixth stage S6, the filter captures aerosols in each collector.

[0071] The device comprises multiple collectors, each with its own filter. These multiple collectors correspond to multiple aerosol sampling points within a flowing fluid. The device allows for the simultaneous collection of several aerosol samples and the study of aerosol homogeneity within the flowing fluid.

[0072] Advantageously, during a seventh step (S7), the quantity of aerosols captured by each filter can be measured, and the overall homogeneity of the aerosols in the flow can be assessed based on the measured quantities. Determining an average quantity of captured aerosols and a standard deviation of the captured quantities allows, for example, this homogeneity to be characterized. This measurement requires first stopping the pump, removing the manifolds, and disassembling the filters. Each filter is then used in a measurement protocol that determines the quantity of aerosols captured by the filter.

[0073] Even more advantageously, during an eighth step S8, an optimal measurement point can be identified corresponding to a collector position that provides an optimal measurement of the amount of aerosols captured. The optimal measurement is the amount of aerosols measured that differs least from the amounts of aerosols measured by the other collectors. For example, the optimal measurement is the one closest to the average amount of aerosols captured.

[0074] It should be noted that, depending on the initial set of measurements, a second set of measurements with more collectors may be necessary. This may be the case, in particular, if the quantities of aerosols captured show significant inhomogeneity.

[0075] In this case, it is possible to remove the duct and manifolds and add new manifolds to device 1. The 24 sections that make up duct 3 can be replaced with shorter sections, each incorporating a portion of a quick-connect fitting. New manifolds may include an elbow fitting, possibly with a variable-length downstream arm, to ensure that the nozzles are not all aligned in the same direction. This configuration allows for more precise measurement of aerosol homogeneity within the flow.

[0076] Method for mounting an aerosol sampling device in a drainage duct

[0077] A sampling system as presented so far can be mounted according to a process Q, the implementation of which we will present with reference to Figure 6. During a first step El, two access ports 30 and 31 are opened in the duct 27. The access ports are inspection ports or openings in the wall of the duct 27 and which allow communication between the inside and outside of the duct 27.

[0078] In a second step E2, an inspection hatch 28 is opened in the duct 27. The inspection hatch is advantageously located downstream of the manifold nozzles once they are installed. Ideally, the hatch is positioned far enough from the nozzle 7 so as not to disrupt the fluid flow at the nozzle 7. The hatch 28 can be placed upstream of the branch connections 30, 31, at the same level, or even downstream. The hatch 28 is positioned close enough to the conduit 3 to allow access to the quick-connect fittings and to attach the manifolds 5 to the conduit 3.

[0079] It should be noted that drainage ducts typically include an access hatch and parallel branch connections, including standard branch connections conforming to the "Pneurop" standard. If this is not the case, it is necessary to drill through the duct to create two branch connections and at least one access hatch. Depending on the accessibility inside the duct, one access hatch may be sufficient for installation, but it may be necessary to drill several hatches.

[0080] In a third step E3, the conduit 3 is inserted into the duct 27 through the access hatch 28. The conduit 3 is pre-assembled before this step. A configuration of the sections 24 is chosen based on the measurement points deemed necessary. The sections 24 are then assembled to form the conduit 3.

[0081] In a fourth step E4, a portion of the conduit 3 is attached to each branch 30, 31. For example, one end of the conduit 3 is inserted into the first branch. This first end could be the end subsequently connected to the vacuum pump 14; the first branch could, for instance, be located opposite the inspection hatch. Then, the second end of the conduit 3 is inserted into the second branch. The fastening components are then mounted on the branches to secure the conduit 3. In a fifth step E5, the conduit 3 is fluidly connected to the vacuum pump 14.

[0082] During a sixth step E6, the collectors 5 are inserted into the duct 27 through the inspection hatch 32.

[0083] The manifolds 5 are assembled prior to this step E6. If necessary, elbow fittings are added to the manifolds 5. The manifolds 5 are not attached to the conduit 3 before being inserted into the duct. The conduit 3 and the manifolds 5 are installed independently.

[0084] In a seventh step E7, each collector 5 is fixed to the conduit 3 so that the collection direction coincides with the fluid flow direction in the duct. Quick-connect fittings, due to their simplicity, allow this fixing to be carried out through the inspection hatch. For example, the female part is fixed directly to the collector, while the male part is fixed directly to the conduit 3. It should be noted that if one of the fixing parts includes an angular reference, it is then possible to position the conduit relative to the duct at a predetermined angular position around a principal extension direction of the conduit, an angular position which, for example, allows the collection direction to be aligned with the fluid flow direction in the duct.

[0085] During an eighth step E8, the inspection hatch 28 and the connections 30, 31 are sealed.

[0086] The sampling system is thus ready to be used, for example according to the previously described process P.

[0087] It should be noted that the sampling device does not require the dismantling of the sheath 27 in order to be able to take a sample of aerosols and moreover a measurement of the homogeneity of the quantities of aerosols captured.

[0088] It should also be noted that in the absence of the device, the spigots 30 and 31 can be hermetically sealed, for example by using for each spigot, a sealing gasket, a plug and a hose clamp.

Claims

DEMANDS 1. Aerosol sampling device (1) comprising: a conduit (3), several collectors (5) in fluidic communication with the conduit (3), each collector (5) extending along a collecting direction (A) and comprising a nozzle (7), a tube (9), a filter (10) configured to capture aerosols, a neck (12) configured to permit critical fluid flow into the collector (5), each tube (9) having an inlet and an outlet and being straight between the inlet and outlet, for each collector a detachable fitting (16) configured to connect or separate the collector (5) and the conduit (3), and a vacuum pump (14) fiducially connected to the collectors (5) via the conduit (3).

2. Aerosol collection device according to claim 1 in which the collectors (5) are arranged parallel to each other and extend along the same collection direction (A), each collector comprising successively in the collection direction the nozzle (7), the tube (9), the filter (10) and the neck (12).

3. Aerosol sampling device according to any one of claims 1 and 2, wherein all or part of the collectors each comprise an elbow fitting (18) which fluidly connects the quick fitting (16) and the neck (12) of the collector (5).

4. Aerosol sampling device according to any one of claims 1 to 3 in which the conduit (3) is formed of a plurality of sections (24) reversibly attachable to each other, each section (24) comprising a part (16B) of a quick coupling (16).

5. Aerosol sampling system (26) comprising a device (1) according to any one of claims 1 to 4 and a flow duct (27), the conduit (3) being fixed to the flow duct (27).

6. Aerosol sampling system according to claim 5, wherein the flow duct (27) comprises two ports (30, 31), each port (30, 31) being configured to receive a portion of the conduit (3), the collectors (5) being placed inside the flow duct so that the collection direction (A) coincides with a main flow direction (E) of the duct.

7. System according to claim 6 comprising two fixing pieces (32) each configured to fix a portion of the conduit to one of the spigots, one of the fixing pieces being configured to block the rotation of the conduit relative to the sheath.

8. System according to claim 7 wherein one of the fixing parts includes an angular reference for placing the conduit relative to the sheath at a predetermined angular position around a principal extension direction (E) of the conduit.

9. Aerosol sampling system according to any one of claims 5 to 8, wherein the conduit is reversibly fixed to the sheath (27).

10. Aerosol sampling system according to any one of claims 5 to 9, wherein the sheath further comprises an inspection hatch (28) configured to permit insertion into the sheath of the duct and collectors.

11. A method for collecting aerosols from a stream, the method comprising the following steps: connecting several collectors (5) to a conduit (3) by means of a detachable fitting (16), arranging in the stream the several collectors (5) extending along a collecting direction (A), reducing the pressure in the conduit (3), generating a critical flow in each collector (5), each collector being fluidly connected to the conduit (3) via a neck (12), isokinetic collection of aerosols from the stream into each collector (5) through a nozzle (7), straight-line transport in each collector of the aerosols, and capture of the aerosols by a filter (10) in each collector.

12. A method according to claim 11 comprising a measurement of the quantity of aerosols captured by each filter and a measurement of the homogeneity of the aerosols in the flow based on the quantities of aerosols measured.

13. Method according to claim 12 further comprising the identification of an optimal measurement point corresponding to a position of the collector providing an optimal measurement of the quantity of aerosols captured, the optimal measurement having a minimum deviation from other measurements of the quantity of aerosols captured.

14. Method of mounting in a flow duct (27) an aerosol sampling device (1) according to any one of claims 1 to 4, the method comprising the following steps: - opening of two spigots (30, 31) in the duct, - opening of an inspection hatch (28) in the duct, - Insertion of the conduit into the duct through the access hatch, - fixing a section of the conduit at each branch connection, - fluid connection of the conduit (3) to the vacuum pump (14), - insertion of the collectors (5) into the duct through the inspection hatch, - fixing each collector to the conduit (3), the collection direction (A) being the same as the flow direction (E) of the fluid in the duct, and - airtight closure of the inspection hatch and the connections.

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