System for creating a laminar flow of sterile air inside a sterilizable environment and related sterilization method

Abstract

Described is a system (1, 101, 201, 301) for forming a laminar flow of sterile air inside a sterilisable environment, comprising: - a sterilisable chamber (10) having, inside it, a diffuser (2) defining a turbulent zone (11) and a laminar zone (12) of the air; - an air inlet line in the turbulent zone (11) actuated by a first fan (3), located in a ventilation zone at the start of the inlet line and having a sterilisable and sterilising delivery filter (4); - an air outlet line from the laminar zone (12), controlled by a first suction device (6), located in an extraction zone at the end of the outlet line and having an outflow filter (5) which is also sterilisable and sterilising; means (23) for adjusting the speed of the air flow in the inlet line as a function of the air pressure difference between the turbulent zone (11) and the laminar zone (12). The invention also relates to the process for sterilising the system (1, 101, 201, 301).

Description

[0001] System for creating a laminar flow of sterile air inside a sterilizable environment and related sterilization method DESCRIPTION

[0002] Technical field

[0003] This invention relates to a system for forming a laminar flow of sterile air inside a sterilisable environment and to the process for sterilising the system.

[0004] Background art

[0005] A laminar flow of air is a type of movement of the air, determined by the internal friction forces, characterised by a uniform and parallel flow of air, without turbulence or vortices. In a laminar flow, the air particles move in parallel layers, with very little or no mixing between them. This type of flow is the opposite of turbulent flow, where the air mixes and moves in an irregular manner.

[0006] In the laminar flow, unlike the turbulent flow, the infinitesimal layers of fluid flow gently over each other, without any mixing occurring, even at a microscopic level.

[0007] Therefore, in laminar flows, since the air moves in a linear and constant manner, the particles maintain a direct path. The dispersion of the particles is minimised, which is essential for maintaining a clean environment.

[0008] For this reason, having a laminar flow of air is particularly useful in environments where it is necessary to reduce to a minimum the presence of contaminants such as dust, bacteria, and other particles, that is to say, in environments where it is essential to maintain a high level of cleaning and sterility, such as in “clean rooms” in the pharmaceutical industry, in the production of semiconductors and in biotechnology. Clean rooms use laminar flows to maintain extremely low levels of contaminating particles in the air.

[0009] Another application of particular interest is that concerning research laboratories and pharmaceutical production, where laminar flows are used for the preparation of sterile drugs, the handling of cell cultures or other activities which require an environment free of contamination.

[0010] Currently, the Applicant does not know any system for forming a laminar flow inside a sterilisable environment, providing a Sterility Assurance Level (SAL) of 1 O’6. This is in contrast with process chambers where less efficient sanitising or disinfection with gas or sprays is performed and non-sterile HEPA filters are used.

[0011] Summary of the invention

[0012] The aim of the invention is therefore to implement a laminar flow of sterile air in a sterilisable environment which guarantees the safety and reliability of the areas in which critical operations are carried out for health, as well as for scientific research and the pharmaceutical industry.

[0013] In the context of the above-mentioned purpose, an aim of the invention is to sterilise a system for forming a laminar flow of sterile air inside a sterilisable environment, that is, free of microbiological contaminants.

[0014] Another aim of the invention is to form a laminar flow inside a sterilised environment, increasing the safety and operational efficiency, protecting both products and components, and ensuring compliance with industry regulations.

[0015] This purpose, as well as these and other aims which are described in more detail below, are achieved by a system for forming a laminar flow of sterile air in a sterilisable environment, according to the invention, comprising the technical features described in one or more of the appended claims. The dependent claims correspond to possible different embodiments of the invention.

[0016] More specifically, according to a first aspect, this invention relates to a system for forming a laminar flow of sterile air inside a sterilisable environment, which comprises inlet and outlet filters which are sterilisable and sterilising, a chamber which can be sterilised with a diffuser inside it which defines a turbulent zone and a laminar zone of the air, converting a turbulent air flow into the flow of laminar air. At the latter there is the process area inside the sterilisable chamber. For this purpose, the sterilisable chamber is advantageously suitable for containing apparatuses for processing parts, filling or handling sterile objects.

[0017] The sterilisable chamber is fed by means of at least one sterilised infeed line of the air in the turbulent zone. The inlet line is actuated by ventilation means, such as at least a first fan, which allow the introduction of the sterile air inside the container. Moreover, the inlet line has a sterilising delivery filter, positioned between the fan and the sterilisable chamber, in such a way as to sterilise the flow of air passing through it.

[0018] Advantageously, this delivery filter, as well as sterilising, can also be sterilised and therefore remains sterile during the entire operation of the system.

[0019] The fan and the ventilation means are located in a ventilation zone which defines the start of the inlet line of the air which is introduced into the sterilisable chamber.

[0020] On the other hand, at least one outlet line discharges air from the laminar zone towards the outside. The outlet line is controlled by suction means, for example by at least a first suction device, in such a way as to extract the air from the container.

[0021] The suction device(s) are positioned in an extraction zone which defines the end of the outlet line of the outflowing air.

[0022] The outlet line comprises a sterilising outflow filter, located between the sterilisable chamber and the suction device.

[0023] Advantageously, the outflow filter can also be sterilised, in such a way as to form a sterile barrier around the sterilisable chamber, preventing microbes and bacteria from penetrating inside it through the inlet and outlet lines.

[0024] In order to be able to guarantee a laminar flow of the air, means are provided for adjusting the speed of the flow of air in the inlet line, as a function of the pressure difference of the air between the turbulent zone and the laminar zone.

[0025] The laminar flow is, as mentioned, characterised by layers of fluid which flow parallel to each other without mixing, determined mainly by the internal friction forces and by the pressure gradient. The viscosity, which represents the internal friction, is proportional to the speed of the fluid. Depending on the speed, therefore, the flow becomes turbulent or laminar, with a passage determined by the Reynolds number.

[0026] In effect, given that the quantity of air to be laminated “Q” depends on the contact surface of the diffuser “S’ and on the air speed “v” according to the formula:

[0027] Q=S v for the flow to be laminar, the speed “v” must be between 0.36 and 0.54 m / s. These adjusting means advantageously comprise a differential sensor which controls the air pressure difference between the turbulent zone and the laminar zone. The differential sensor is operatively connected with the ventilation means and modifies the speed of the flow of air in the inlet line according to the data measured, according to the measured value of the pressure difference of the air between the turbulent zone and the laminar zone, in such a way as to guarantee in any case the formation of a laminar flow inside the sterilisable chamber, in the passage of the air from the diffuser, that is, from the turbulent zone to the laminar zone.

[0028] Together with or as an alternative to the differential sensor, it is possible to install a flow rate regulator, mounted in the inlet line between the ventilation means and the delivery filter. The device ensures that the flow has a flow rate such as to satisfy the laminar requirements.

[0029] In practice, if the differential sensor acts on the speed “v” to modify it so as to have a predetermined flow rate “Q”, the flow rate regulator acts directly on the flow rate “Q” without the need to check the pressure inside the sterilisable chamber.

[0030] At the same time, advantageously, a pressure sensor is installed for the air flowing out from the laminar zone which, communicating with the suction means, regulates the flow of the air flowing out from the sterilisable chamber.

[0031] In other words, the pressure sensor is operatively connected with the first suction device for modifying the speed of the air outlet line, in such a way as to guarantee that the pressure recorded by the pressure sensor is always at a predetermined value.

[0032] Depending on the type of production, that is to say, the process in progress in the sterilisable chamber, the predetermined value may be greater or less than the outside pressure.

[0033] Such a system therefore allows the formation of a laminar flow in a sterilisable environment.

[0034] In order to overcome the possible head losses of the delivery and outflow filters, the Applicants have advantageously prepared a series of lines for inlet of the air in the turbulent zone, mounted in parallel, and as many lines for the outlet of the air from the laminar zone, which are also positioned in parallel, in such a way as to form batteries of delivery and outflow filters.

[0035] The infeed lines of the series are all actuated by a respective fan, preferably together with an auxiliary fan, and each have a respective sterilising and sterilisable delivery filter. In the same way, each outlet line is controlled by a respective suction device and has a relative sterilising and sterilisable outflow filter.

[0036] Another technical problem which the Applicants have overcome is linked to the temperature of the air flowing out from the sterilisable chamber, which cannot exceed a predetermined threshold value, of approximately 80°C, beyond which the suction device would be compromised.

[0037] For this purpose, means have been provided for controlling the temperature of the air flowing out from the lamination zone, that is to say, along the outlet line, in such a way that the air which arrives at the extraction zone (and which passes through the first suction device) has a temperature less than the predetermined threshold value.

[0038] These means may be alternative to each other even if a configuration in which they are present together is not excluded.

[0039] According to a first solution, the control means comprise the injection of compressed air along the injection line, between the fan and the delivery filter, at a pressure such as to overcome the pressure of the delivery filter and of the outflow filter and, at the same time, the discharge outside of the air flowing out before it can reach the suction device by means of a bypass type connection, positioned along the outlet line downstream of the outflow filter, that is to say, between the outflow filter and the suction device, in such a way that the quantity of excess air is expelled.

[0040] In this way, the hot air escapes from the bypass preventing the arrival in the extraction zone.

[0041] A variant comprises the use of a cooling battery, that is to say, a so-called “cooler” mounted along the outlet line, between the outflow filter and the extraction zone. The cooling battery has a coil which cools the hot air arriving from the lamination zone to a temperature which will be below the predetermined threshold value.

[0042] In another embodiment, the control means comprise a conduit for injecting compressed air, positioned downstream of the outflow filter along the outlet line, before the extraction zone, which may introduce into the outlet line predetermined quantities of compressed air to be mixed with the air flowing out from the lamination zone. Both the quantity and the temperature of the air introduced in the outlet line are such that the mixture of air obtained has a temperature below the predetermined threshold value.

[0043] Patent protection is also required for a method for sterilising a system for forming a laminar flow of sterile air wherein the laminar flow of sterile air comes from a sterilisable and sterilising filter.

[0044] The above-mentioned method comprises the following steps. The fans and suction devices are disconnected from the respective air lines (inlet and outlet), thus isolating the ventilation and aspiration zones from the rest of the system.

[0045] A part of the inlet line, downstream of the ventilation zone but before the sterilisable chamber, which comprises the delivery filter, is therefore isolated from the rest of the system, in such a way as to have a first portion and a second portion of the system hermetically separated from each other: the first portion of the system will comprise the sterilisable and sterilising delivery filter and a part of the inlet line, the second portion of the system will comprise the other part of the inlet line, the sterilisable chamber, the outflow filter, which is also sterilisable and sterilising, and the outlet line (up to the extraction zone).

[0046] Sterilising steam is injected, at high pressure, in the first portion of the system, preferably upstream of the delivery filter.

[0047] After sterilising the first portion, other high pressure steam is injected in the second portion of the system, preferably inside the sterilisable chamber, so as to sterilise the remaining part of the inlet line, the inside of the sterilisable chamber, the outlet line and the outflow filter.

[0048] The communication between the first and second portions of the system is restored, and the previously insulated ventilation and suction zones are reconnected.

[0049] Description of the drawings

[0050] Further features and advantages of the invention are more apparent in the detailed description below, with reference to a preferred, non-limiting embodiment of the system for forming a laminar flow of sterile air in a sterilisable environment, illustrated by way of example and without limiting the scope of the invention, with the aid of the accompanying drawings, in which:

[0051] Figure 1 schematically shows a first embodiment of the system 1 for forming a laminar flow of sterile air inside a sterilisable environment, according to the invention;

[0052] Figure 2 schematically shows another embodiment of the system 101 , with an injection conduit 107 of compressed air and a connection 108 for discharging outside the air flowing out from the lamination zone, for controlling the temperature of the air along the outlet line;

[0053] Figure 3 shows a variant of the system 201 , wherein there is a cooling battery 209 for adjusting the temperature of the air along the outlet line;

[0054] Figure 4 schematically shows a further variant of the system 301 , wherein the means for controlling the temperature of the air flowing out from the laminar zone 12 comprise a conduit 307 for injecting compressed air;

[0055] Figure 5A schematically illustrates the first step of sterilising the system 1 , with a double filtering system, wherein superheated steam is injected into the first portion of the system 1 ;

[0056] Figure 5B schematically illustrates the second step of sterilising the system 1 of Figure 5A, wherein superheated steam is injected into the second portion of the system 1 .

[0057] Detailed description

[0058] The above-mentioned drawings show a preferred embodiment of a system for forming a laminar flow of sterile air inside a sterilisable environment, according to the invention, which is identified in its entirety with the numeral 1 and which comprises a sterilisable chamber 10 which, inside it, has a diffuser 2, for example made of stainless steel, which defines a turbulent zone 1 1 and a laminar zone 12 of the air inside the sterilisable chamber 10. At the laminar zone 12 there is the process area, that is to say, the operating zone which is necessarily sterile.

[0059] The sterilisable chamber 10 is fed by an inlet line of the air which starts from a ventilation zone, where a first fan 3 (Figure 1 ) and / or 3a (Figures 5A and 5B) is mounted and, if necessary, an auxiliary fan 3’ (Figures 2-4), and ends inside the sterilisable chamber 10 through a respective outlet in the turbulent zone 1 1 .

[0060] The air entering is rendered sterile by a sterilisable delivery filter 4 interposed between the ventilation zone and the sterilisable chamber 10. On the other hand, there is an outlet line of the air which starts from another outlet of the sterilisable chamber 10 defined at the laminar zone 12, and leads towards an external discharge moved by suction means (a suction device 6 and / or 6a and, if necessary, an auxiliary suction device 6’), installed in an extraction zone.

[0061] In other words, the inlet line leads from the ventilation zone, where the ventilation means (the fans 3 and / or 3a and, if necessary, the auxiliary fan 3’) are located to the sterilisable chamber 10, close to its outlet inside the turbulent zone 12; the outlet line extends from the outlet of the sterilisable chamber 10 (located in the laminar zone 1 1 ) to the extraction zone, where the suction means (the suction devices 6 and / or 6a and, if necessary, the auxiliary suction device 6’) are mounted.

[0062] An outflow filter 5, which is also sterilisable and sterilising, is positioned between the sterilisable chamber 10 and the extraction zone.

[0063] The sterile air flowing out passes from an outflow filter 5, which is also sterilisable and interposed between the sterilisable chamber 10 and the extraction zone.

[0064] The delivery filter 4 and the outflow filter 5, both of a diaphragm and hydrophobic type, sterilise the flow of air passing through them, in practice forming a sterile barrier around the sterilisable chamber 10.

[0065] The system comprises the installation of a differential sensor 23 for controlling the air pressure difference between the turbulent zone 1 1 and the laminar zone 12.

[0066] The air must have a speed such as to guarantee that the laminar flow is created inside the sterilisable chamber 10, when the turbulent air passes from the turbulent zone 11 to the laminar zone 12 passing through the diffuser 2.

[0067] For this purpose, the differential sensor 23 is operatively connected with the first fan 3 (and / or 3a and / or the auxiliary fan 3’) in such a way that, depending on the value of the air pressure difference between the turbulent zone 1 1 and the laminar zone 12, the speed of the air inlet line is modified, to guarantee laminar flow speeds of between 0.36m / s and 0.54m / s.

[0068] In the proximity of the outlet of the air flowing from the turbulent zone 12, on the other hand, a pressure sensor 26 has been installed which constantly measures the pressure of the air before it enters the outlet line.

[0069] In order avoid the backflow of the air from the outside to the inside, which could adversely affect the laminar nature of the flow of air in the laminar area 12 and could put at risk the sterility of the sterilisable chamber 10, it is necessary that the pressure of the air in the process chamber is at a predetermined value.

[0070] Therefore, the pressure sensor 26, which is operatively connected with the first suction device 6 (and / or 6a and / or the auxiliary suction device 6’), controls the speed of the air outlet line and the modification when appropriate, in such a way as to guarantee that the pressure recorded by the pressure sensor 26 is always at a predetermined value, which may be greater than or less than the external pressure, depending on the industrial process operated in the sterilisable chamber 10.

[0071] The connections between the sensor means 23 and 26 and the respective fan 3 and suction device 6 are shown in the accompanying drawings with broken lines.

[0072] In order have a sufficient power, use is made of one or more auxiliary fans 3’, mounted in line with the first fan 3 in the ventilation zone, and / or one or more auxiliary suction devices 6’, similarly installed in line with the first suction device 6 in the extraction zone.

[0073] In order to contain the head losses of the delivery filter 4 and outflow filter 5, the assembly of delivery filters 4 and 4a and outflow filters 5 and 5a is provided in parallel, as shown in Figures 5A and 5B.

[0074] In this case, a series of air inlet lines are formed in the turbulent zone 1 1 , each operated by a relative fan 3 and 3a with respective delivery filter 4 and 4a, which are both sterile and sterilising, and a series of lines for outlet of the air from the laminar zone 12, each controlled by a respective suction device 6 and 6a and equipped with the corresponding outflow filter 5 and 5a, which are both sterile and sterilising.

[0075] The series of inlet and outlet lines and the respective fans 3 and 3a and suction devices 6 and 6a operate in a coordinated fashion, each with the same principle described above and based on the control of the flow speed served both by the differential sensor 23 and by the pressure sensor 26.

[0076] For adjusting the temperature of the air flowing out from the laminar zone 12, means are provided for controlling the temperature of the air flow. These control means, which are located along the outlet line upstream of the extraction zone, ensure that the air which passes through the first suction device 6 (or 6a and / or 6’) has a temperature less than a predetermined threshold value, for example 80°C, above which the suction device 6 (6a, 6’) could be damaged.

[0077] Figure 2 illustrates a first diagram, in which the control means comprise an injection conduit 107 for introducing compressed air into the inlet line. The injection conduit 107 is positioned upstream of the delivery filter 4, between the ventilation zone and the delivery filter 4 and is designed to introduce compressed air into the inlet line at a pressure such as to overcome the pressure of the delivery filter 4 and of the outflow filter 5. Moreover, on the opposite side, in the outlet line, a connection 108 is prepared, located between the outflow filter 5 and the extraction zone, which allows the discharge of the air flowing out from the lamination zone 12 to the outside of the system, in such a way that the quantity of hot air in excess is expelled so as to bring the temperature of the air at the outlet below the predetermined threshold value.

[0078] Another solution, shown in Figure 3, comprises installing, along the outlet line, a cooling battery 209 for cooling the air flowing out from the lamination zone 12 to a temperature at least below the predetermined threshold value. The cooling battery 209, equipped with a suitable coil, is interposed between the outflow filter 5 and the extraction zone.

[0079] With reference to Figure 4, a third variant of the control means is that in which a conduit 307 is mounted for injecting compressed air, positioned - along the outlet line - between the outflow filter 5 and the extraction zone. The injection conduit 307 allows small portions of compressed air to be introduced in the air flow flowing out, at a suitable temperature for mediating the temperature of the air intended for the extraction zone.

[0080] In other words, compressed air is introduced into the outline line through the injection conduit 307 to be mixed with the air flowing out from the lamination zone 12, in a quantity and at a temperature such that the mixture of air obtained is below the predetermined threshold value.

[0081] For the sterilisation of the system 1 (101 , 201 , 301 ) the ventilation zone and the extraction zone are firstly isolated from the rest of the system.

[0082] In this regard, as shown in Figures 5A and 5B, the inlet valves R1 and outlet valves P4 are closed, located in the air inlet line and in the outlet line. The inlet valve R1 is interposed, in each inlet line, between the ventilation zone and the delivery filter 4 (4a); the outlet valve P4 is, in each outlet line, between the outflow filter 5 (5a) and the extraction zone.

[0083] In that way, the ventilation means (3, 3a, 3’) and the suction means (6, 6a, 6’) are disconnected from their corresponding air inlet and outlet lines.

[0084] With reference to Figure 5A, a part of the inlet line, comprising the delivery filter 4 (4a), is also isolated from the rest of the system 1 (101 , 201 , 301 ) acting on the double valve systems consisting of the valves P2 and P3, respectively first and second valve, positioned one after another in the inlet lines, between the delivery filter 4 (4a) and the sterilisable chamber 10.

[0085] In this way, there is a first portion and a second portion of the system 1 (101 , 201 , 301 ) which are hermetically separated from each other.

[0086] The first portion, which leads from the inlet valve P1 to the double valve P2- P3, comprises a part of the inlet line and the delivery filter 4 (4a).

[0087] The second portion, which leads from the double valve P2-P3 to the outlet valve P4, comprises a part of the inlet line (from the double valve P2-P3 to the sterilisable chamber 10), the sterilisable chamber 10 itself, obviously included inside, the outflow filter 5 (5a) and the outlet line up to the outlet valve P4.

[0088] After also closing the second valve P3 leaving the first valve P2 open, saturated sterilising steam is injected in the first portion of the system 1 (101 , 201 , 301 ) by means of an injector 7 (7a) positioned upstream of the delivery filter 4 (4a). For collecting the condensate, preferably continuously, each inlet line comprises a special tank V, preferably connected to the double valve P2-P3 (Figure 5A).

[0089] Upon completion of the sterilisation of the first portion, the first valve P2 is closed and the second valve P3 is opened, saturated steam is injected in the second portion of the system 1 (101 , 201 , 301 ), by means of a conduit 17, inside the sterilisable chamber 10. In this way it is possible to sterilise the remaining part of the inlet line, from point P2 to the sterilisable chamber 10, the inside of the sterilisable chamber 10, the outflow filter 5 (5a) and the outlet line up to point P4. In this case, too, for each outlet line there is the tank V for collecting the condensate, preferably connected to point P4 (Figure 5B).

[0090] Obviously, the stretch of the inlet line between the valves P2 and P3 will be subjected to a double sterilisation. The sterilisation superposition is useful to ensure that no point in this stretch remains uncovered.

[0091] Once the sterilisation has been completed, the first and second portions of the system 1 (101 , 201 , 301 ) are placed in communication acting on the double valve P2-P3 and, subsequently, the ventilation and suction zones are also reconnected to the rest of the system acting on the valves positioned at the inlet valve P1 and the outlet valve P4.

[0092] From the above description it may be seen how the invention achieves the preset purpose and aims and in particular it should be noted that a system is made for forming a laminar flow of sterile air inside a sterilisable environment, which guarantees a high standard of reliability in areas intended for sterile processes.

[0093] In particular, the formation of an aseptic barrier around the sterilisable chamber, in which sterile products are to be processed, obtained thanks to the use of sterile filters instead of conventional HEPA filters, and the easy adjustment of the laminar flow, create an environment free of microbiological contaminants.

[0094] Another advantage of the invention is the possibility of sterilising a system for forming such a laminar flow of sterile air in a simple and fast manner.

[0095] Last but not least, a sterile laminar flow is formed through a system, according to the invention, inside a controlled and contamination-free environment, increasing safety and operating efficiency, protecting both products and components, and ensuring compliance with industry regulations.

[0096] The invention can be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all the details of the invention may be substituted by other technically equivalent elements.

[0097] In practice, the materials used, as well as the dimensions, may be of any type, depending on requirements, provided that they are consistent with their production purposes.

Claims

CLAIMS1 ) A system (1 , 101 , 201 , 301 ) for forming a laminar flow of sterile air inside a sterilisable environment, comprising: a sterilisable chamber (10) having, inside it, a diffuser (2) defining a turbulent zone (11 ) and a laminar zone (12) of the air; an air inlet line in the turbulent zone (11 ) actuated by a first fan (3), located in a ventilation zone at the start of the inlet line and having a sterilising sterilisable delivery filter (4); an air outlet line from the laminar zone (12), controlled by a first suction device (6), located in an extraction zone at the end of the outlet line and having a sterilising outflow filter (5); means (23) for adjusting the speed of the air flow in the laminar zone (12).2) The cycle (1 , 101 , 201 , 301 ) according to claim 1 , comprising a sensor (26) of the pressure of the air of the laminar zone (12); said pressure sensor (26) being operatively connected with the first suction device (6) for modifying the speed of the air outlet line in such a way as to guarantee that the pressure of the laminar zone (12) recorded by said pressure sensor (26) is always at a predetermined value.3) The cycle (1 , 101 , 201 , 301 ) according to claim 1 or 2, comprising an auxiliary fan (3’) mounted in line with the first fan (3) in the ventilation zone, and / or an auxiliary suction device (6’) mounted in line with the first suction device (6) in the extraction zone.4) The cycle (1 , 101 , 201 , 301 ) according to any one of claims 1 to 3, comprising: a series of air inlet lines in the turbulent zone (11 ), each actuated by a respective fan (3, 3a) and having a relative sterilising delivery filter (4, 4a); and a series of air outlet lines from the laminar zone (12), each controlled by arespective suction device (6, 6a) and having a relative sterilising outflow filter (5, 5a).5) The cycle (101 ) according to any one of claims 1 to 4, wherein said adjusting means (23) comprise a differential sensor (23) for detecting the air pressure difference between the turbulent zone (11 ) and the laminar zone (12); said differential sensor (23) being operatively connected with the first fan (3) in such a way that, depending on the value of the air pressure difference between the turbulent zone (1 1 ) and the laminar zone (12), the speed of the air in the laminar zone (12) is modified.6) The cycle (101 ) according to any one of claims 1 to 4, wherein said adjusting means (23) comprise a regulator of the flow rate of the air in the inlet line operatively connected with the first fan (3), in such a way as to modify the speed of the air in the laminar zone (12).7) The system (101 ) according to any one of claims 1 to 4, comprising means (107, 108, 209, 307) for controlling the temperature of the air flowing out from the laminar zone (12), along the outlet line, in such a way that the air which passes through the first suction device (6) has a temperature less than a predetermined threshold value.8) The system (101 ) according to claim 7, wherein said control means (107, 108, 209, 307) comprise: a conduit (107) for injecting compressed air, positioned, along the injection line, upstream of the delivery filter (4) suitable for introducing compressed air into the inlet line at a pressure such as to overcome the pressure of the delivery filter (4) and of the outflow filter (5); a connection (108), located along the outlet line, for discharging to the outside the air flowing out from the lamination zone (12), downstream of theoutflow filter (5), in such a way that the excess quantity of air is expelled in order to bring the temperature of the air flowing out below the predetermined threshold value.9) The system (201 ) according to claim 7, wherein said control means (107, 108, 209, 307) comprise, along the outlet line, a cooling battery (209) for cooling the air flowing out from the laminar zone (12), downstream of the outflow filter (5), below the predetermined threshold value.10) The system (301 ) according to claim 7, wherein said control means (107, 108, 209, 307) comprise a conduit (307) for injecting compressed air, positioned downstream of the outflow filter (5) along the outlet line and suitable for introducing in the outline line compressed air to be mixed with the air coming out from the laminar zone (12), with a quantity and at a temperature such that the mixture of air obtained is below the predetermined threshold value.1 1 ) A method for sterilising the system (1 , 101 , 201 , 301 ) according to any one of claims 1 to 10 for forming a laminar flow of sterile air coming from the sterilisable and sterilising delivery filter (4, 4a), comprising the steps consisting in:- isolating the ventilation zone and the extraction zone from the rest of the system, disconnecting fans (3, 3’) and suction devices (6, 6) respectively from the air inlet line towards the turbulent zone (11 ) of the sterilisable chamber (10) and from the outlet line air coming out from the laminar zone (12) of the sterilisable chamber (10),- isolating a part of the inlet line comprising the delivery filter (4, 4a), from the rest of the system (1 , 101 , 201 , 301 ), in such a way as to have a first portion and a second portion of the system (1 , 101 , 201 , 301 ) which are hermetically separated from each other,- injecting sterilising steam in the first portion of the system (1 , 101 , 201 ,301 ), preferably upstream of the delivery filter (4, 4a) and, upon completion of the sterilising of the first portion, injecting sterilising steam in the second portion of the system (1 , 101 , 201 , 301 ), preferably inside the sterilisable chamber (10), so as to sterilise the remaining part of the inlet line, the inside of the sterilisable chamber (10), the outlet line and the outflow filter (5, 5a) which can be sterilised, and preferably sterilising,- putting into communication the first and the second portion of the system (1 , 101 , 201 , 301 ).

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