WO2012150571A1

WO2012150571A1 - A particle collector apparatus

Info

Publication number: WO2012150571A1
Application number: PCT/IB2012/052227
Authority: WO
Inventors: Malcolm Smith
Original assignee: Malcolm Smith
Priority date: 2011-05-04
Filing date: 2012-05-03
Publication date: 2012-11-08
Also published as: GB2504442A; GB201320498D0; GB2490509A; GB201107328D0; GB2504442B

Abstract

Particle collector apparatus are used to separate particles from an entrained gas. Typically, flow is effected by means of applying a vacuum at one end, where the vacuum is produced by means of a mechanical, reciprocating piston, type vacuum generator. The present invention provides a particle collector apparatus (10), for use in testing medical devices which emit particulates, such as inhalers, comprising a collection vessel (210) having an inlet (230), for connection with the device to be tested, and an outlet (240), and a first vacuum generating unit (10) connected to the outlet, wherein the first vacuum generating unit is powered by of a first vacuum-forming fluid to produce a first at least partial vacuum thereby inducing a flow of a first sample fluid in a first direction through the collection vessel (210) from the inlet to the outlet, wherein the collection vessel is an impactor or an impinger.

Description

A particle collector apparatus

The present invention relates generally to a particle collector apparatus and to a method of collecting particles entrained in a fluid, and finds particular, although not exclusive, utility in the assessment of medical devices such as inhalers.

In this regard, the term inhaler refers to medical devices used by, for example, asthma sufferers for the dispensation and inhalation of pharmaceutical compositions.

In the development of inhalers it is necessary to test their operation. One of the areas requiring testing is the quantification of the different sizes of particles dispensed during use. In one embodiment, particle collection vessels including a series of sieves or filters for collecting particles of differing sizes are used. However, these are not effective as they tend to become blocked very easily and/or merely collect everything rather than different size fractions.

This may be useful in some circumstances where it is necessary to collect the particles of all sizes as they exit the inhalers in use. The particles may be then analysed as required. The collection vessels may be dose collection tubes and may include filters for trapping the particles.

To mimic the effect of use a suction force, or at least a partial vacuum, must be produced at the outlet of the inhaler and the outlet must be fluidly connected to the particle collection vessel.

The suction force is typically produced using a vacuum generator of the pump-type including a reciprocating piston and possibly an air receiver. However, these pumps suffer from mechanical failure, and are noisy and bulky. Furthermore, it is difficult to control the vacuum force effected through the particle collection vessel in a fast and consistent manner leading to disparities in results from several identical tests. This is because as the pumps warm-up their characteristics change over time. For the testing of medical devices such as inhalers certain jurisdictions, such as the FDA in the USA, require strict procedures to be followed such as the requirement for constant and regular fluid flow rates.

It would therefore be desirable to have an improved apparatus and method for testing such inhalers.

In a first aspect, the invention provides a particle collector apparatus, for use in testing medical devices which emit particulates, such as inhalers, comprising a collection vessel having an inlet, for connection with the device to be tested, and an outlet, and a first vacuum generating unit connected to the outlet, wherein the first vacuum generating unit is powered by movement of a first vacuum-forming fluid to produce a first at least partial vacuum thereby inducing a flow of a first sample fluid in a first direction through the collection vessel from the inlet to the outlet, wherein the collection vessel is an impactor or an impinger.

The impactors or impingers may include one or more conduits including array(s) of bends which operate to collect different sized particles as they drop-out of their entrainment by virtue of inertia. The impactors or impingers may operate with different types of fluids such as water and air. The particulates may be initially relatively dry.

In this manner, the vacuum is not generated by apparatus of the type including a reciprocating piston. Rather, the vacuum generating unit of the invention has no moving parts. The vacuum generating unit may be of the type similar to those which comprise a moving flow of a first fluid in a conduit, the conduit having a branch pipe. An at least partial vacuum is created in the branch pipe as the first fluid moves past its junction with the conduit. Such devices may be known as flow amplifiers. One of the characteristics of these devices is that they may effect a relatively large volume flow rate and/or pressure change in the first sample fluid by virtue of only a relatively small change in the pressure and/or volume flow rate of the first vacuum-forming fluid, in a similar manner to an electrical transistor.

Alternatively or additionally, the first vacuum generating unit may rely upon the Coander effect and/or Bernoulli principle in operation to produce the first at least partial vacuum.

The first sample fluid may be drawn through the collection vessel from the inlet to the outlet by a suction force induced by the first at least partial vacuum, and the apparatus may be arranged such that this first sample fluid mixes with the first vacuum-forming fluid in the first vacuum generating unit.

The first fluid may be compressed air. It may have a pressure of approximately 6 bar. Accordingly, the source of energy for operating the vacuum generating unit may be provided in reusable gas bottles and/or an air receiver filled by a compressor. The release of the compressed air from its source may be by means of a relatively small and easily electrically controllable regulator valve.

The apparatus may include a controller arranged to monitor the flow rate of the first sample fluid exiting the collection vessel and variably adjust, as necessary, the pressure and/or volume flow rate of the first vacuum-forming fluid through the first vacuum generating unit so as to maintain the flow rate and/or pressure of the first sample fluid at a predetermined value.

In this way the suction force created by the first vacuum generating unit may be finely controlled in that the flow of first vacuum-forming fluid (possibly from the source of compressed gas) may be throttled or otherwise regulated to produce a consistent volume flow rate and/or pressure. The controller may be a flow regulator.

The apparatus may comprise a second vacuum generating unit powered by movement of a second vacuum-forming fluid to produce a second at least partial vacuum thereby inducing a flow of a second sample fluid in a second direction through the collection vessel, wherein the second direction is substantially opposite to the first direction. Various valves may be included to isolate one or both of the two vacuum generating units from the collection vessel.

The two vacuum generating units may be connected in series or parallel.

The controller may be arranged to monitor the flow rate of the second sample fluid entering the collection vessel and variably adjust, as necessary, the pressure and/or volume flow rate of fluid through the second vacuum generating unit so as to maintain the flow rate and/or pressure of the second sample fluid at a predetermined amount.

The apparatus may comprise one or more flow meters for measuring the rate of flow of the first and/or second sample fluid(s). The flow meter(s) may be arranged downstream of the collection vessel thus not impeding the flow of fluid into the inlet of the collection vessel.

The apparatus may comprise one or more pressure gauges for measuring the pressure of the first and/or second vacuum-forming fluid(s).

The various pressure gauge and flow meters may be connected to the controller.

The apparatus may comprise an exhaust fluid trap for trapping the fluid exiting the collection vessel. This fluid may be the first and second fluids mixed together. The trap may be a water trap although other types are contemplated.

The apparatus may include an automatically controllable valve for controlling the pressure in the collection vessel such that a leak test is performable on the collection vessel. In this way, the inlet to the collection vessel may be blocked and the vacuum generating unit used to create a vacuum in the collection vessel. The valve may then be used to isolate the collection vessel from the vacuum generating unit and a pressure gauge used to determine if there is a leak in the collection vessel. The controller may be arranged to undertake this leak test automatically.

The apparatus may include medical device holding and moving equipment for variously holding the exit of the medical device in front of the inlet of the collection vessel, activating the medical device to emit particulates, shaking the medical device, and removing the medical device away from the inlet of the collection vessel, wherein the medical device holding and moving equipment is arranged to cooperate with collection vessels having various inlet positions.

In this way collection vessels with inlets at different heights may be accommodated.

Although the apparatus has been described for use with medical devices it will be understood by the skilled person that it could be used with other devices such as scuba diving equipment.

In a second aspect, the invention provides a particle collector apparatus, for use in testing medical devices which emit particulates, such as inhalers, comprising a collection vessel having an inlet, for connection with the device to be tested, and an outlet, and a first vacuum generating unit connected to the outlet, wherein the first vacuum generating unit is powered by movement of a first vacuum-forming fluid to produce a first at least partial vacuum thereby inducing a flow of a first sample fluid in a first direction through the collection vessel from the inlet to the outlet, wherein the collection vessel is one or more of an impactor, an impinger, a dose collection tube, or any other collection means for collecting and possibly separating the particles into fractions. The fractions may be based upon any one of size, weight and density of the particles.

In a third aspect, the invention provides a method of collecting particles entrained in a first sample fluid comprising the steps of providing apparatus according to either of the first or second aspects, providing a source of particles in fluid connection with the inlet of the collection vessel, providing a first vacuum-forming fluid, controlling the flow of the first vacuum-forming fluid through the first vacuum generating unit thereby inducing a flow of a first sample fluid through the collection vessel thus sucking in particles from the source of particles.

The first vacuum-forming fluid may be compressed air. The first sample fluid may be air. The method may involve the mixing of the two fluids together due to the operation of the vacuum generating unit.

The method may further comprise the steps of providing a second vacuum generating unit, connecting it to the collection vessel, and controlling the first and second vacuum generating units to provide a flow of fluid through the collection vessel which alternates in direction thereby to simulate breathing.

In this way the test may more closely simulate actual use of an inhaler in that a user may not always just suck through it but may also breathe in and out through it.

In a fourth aspect, the invention provides a medical device particle collector apparatus comprising a collection vessel having an inlet, for connection with the device to be tested, and an outlet, and a first vacuum generating unit connected to the outlet, wherein the first vacuum generating unit is powered by movement of a first vacuum-forming fluid to produce a first at least partial vacuum thereby inducing a flow of a first sample fluid in a first direction through the collection vessel from the inlet to the outlet, wherein the collection vessel is an impactor or an impinger. The various embodiments described above with regard to the first aspect apply equally to this forth aspect. The medical device may be an inhaler.

It will be understood by the skilled person that such equipment allows for far better testing of inhalers and other such inhalation equipment in that it is more controllable, consistent, quieter in use and also relatively less expensive.

The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

Figure 1 is a cross-section of a vacuum generating unit according to one embodiment of the invention

Figure 2 is a schematic plan of one particle collection apparatus; and

Figure 3 is a schematic plan of another particle collection apparatus.

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Similarly, it is to be noticed that the term “connected”, used in the description, should not be interpreted as being restricted to direct connections only. Thus, the scope of the expression “a device A connected to a device B” should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means. “Connected” may mean that two or more elements are either in direct physical or electrical contact, or that two or more elements are not in direct contact with each other but yet still co-operate or interact with each other.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may refer to different embodiments. Furthermore, the particular features, structures or characteristics of any embodiment or aspect of the invention may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form yet further embodiments, as will be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practised without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

In the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

The invention will now be described by a detailed description of several embodiments of the invention. It is clear that other embodiments of the invention can be configured according to the knowledge of persons skilled in the art without departing from the true spirit or technical teaching of the invention, the invention being limited only by the terms of the appended claims.

In Figure 1 a cross-section of a vacuum generating unit 10 is depicted. It is of the type sold by Vaccon Company, Inc. as a material conveying pump.

The pump 10 comprises a cylindrical body 20 having a bore comprising a central section 80 which has a substantially constant diameter, an inlet 90 having a bore which increases in diameter from the constant diameter of the central section to the axial end of the cylindrical body 20, and an outlet 100 also having a bore which increases in diameter from the constant diameter of the central section to the opposite axial end of the body 20.

A second cylindrical body 30 is provided immediately radially outside of the body 20 in the form of a ring, at a point approximately one-third of the axial length of the body 20 from one axial end thereof.

This second cylindrical body has an orifice 40 which leads into an inner annulus 50 provided as a hollow chamber in the form of ring within the cylindrical body 20. This annulus 50 is connected to the central section of the bore of the body 20 by an array of passages 60. These passages are arranged such that their axial lengths are at an angle of approximately 45 degrees to the longitudinal axis of the body 20. They open into the central bore 80.

In use, compressed fluid, such as air, is directed into the orifice 40 in the direction as shown. It is forced (by its relatively high pressure) into the annulus 50 and thus via the passages 60 into the central section of the body 20.

Due to the Coander effect as the air passes from the passages into the central bore 80 its speed increases. The air then passes out of the unit 10 via the outlet 100 in the direction shown.

Due to the arrangement of the passages 60 the air forms into a corkscrew rotating as it progresses down the bore 20 to the outlet 100.

The Bernoulli effect of decreased pressure with increased speed ensures that a lower pressure is produced at the inlet 90 of the unit 10. This may be considered to be a vacuum, or a partial vacuum, or merely an area of reduced pressure. However, it produces a sucking effect at the inlet 90 which may be utilised as described below.

In Figure 2, a particle collection apparatus (or inhaler testing apparatus) 200 is shown. It includes a particle collection vessel 210 comprising an inlet 230 at the top and an outlet 240 at the base. The vessel includes collection means for collecting various sizes of particles such that after use the different size fractions may be quantified.

Aimed into the inlet 230 of the vessel 210 is an inhaler 410. The inhaler is held by an apparatus 400 which comprises a base, an upright telescopic arm for height adjustment, and a means of activating the inhaler (not shown). The apparatus 400 allows the inhaler to be activated, moved towards the inlet 230, moved away from the inlet 230, shaken and have a variable operating position (height/angle adjustment). In one embodiment, rather than the inhaler 410 being moved away and towards the inlet 230, the particle collection apparatus is moved towards and away from the inhaler and equipment to achieve this is provided (not shown).

The outlet 240 is connected to the inlet of a vacuum generating unit 10 by a pipe 250. The outlet 100 of the vacuum generating unit 10 is connected to a fluid trap 270. This trap is optional and may comprise water for trapping gases or particles which have not been caught within the particle collection vessel.

The vacuum generating unit, or flow amplifier, 10 is powered by compressed air fed from a source of compressed air 290. This source is connected via a regulator 295.

A flow meter 285 is shown monitoring the rate of flow flowing between the particle collection vessel 210 and the vacuum generating unit 10. Another flow meter 300 is shown monitoring the rate of flow of compressed air flowing into the vacuum generating unit 10 from the source of compressed air 290. Either or both of these

flow meters

285, 300 are optional and may alternatively or additionally comprise of pressure gauges.

A controller 280 is provided for controlling the apparatus 200. It is connected to the

meters

285, 300, the source of compressed gas 290 and the regulator 295 regulating the flow of compressed gas from the source 290 to the vacuum generating unit 10. It is also connected to a motorised valve 298.

The controller 280 may include a CPU and/or be connected to a computer. In this way, the apparatus 20 may be controlled such that a consistent suction force (or reduced pressure) is applied to the outlet of the particle collection vessel 210 such that, in use, the inhaler 410, or other such subject for testing, may be connected to the inlet 230 and have air or other fluids pulled through it.

This control may be effected by way of a feedback loop control, in that the regulator 295 is substantially constantly controlled to adjust the pressure/volume flow rate of compressed gas from the source 290 in response to the measured pressure/flow rate of the air exiting the collection vessel 210.

A leak test may be conducted by blocking the inlet 230, opening the motorised valve 298, activating the flow amplifier 10 to create at least a partial vacuum in the vessel 210, closing the valve 298 and monitoring the pressure gauge 285. If there is a leak the pressure will increase over time. The controller 280 may undertake this test automatically and provide an indication as to whether or not a leak is present (a leak being defined by predefined conditions).

Figure 3 shows a variation of the apparatus in Figure 2. The apparatus 201 includes all the same equipment, viz. the particle collection vessel 210, a vacuum generating unit 10, a gas trap 270, a controller 280, a source of compressed air 290, a flow regulator 295 and flow

meters

285, 300. Accordingly, one way of operation involves the flow of compressed air A’ from the source of compressed air 290 to the vacuum generating unit 10 such that it pulls air or other fluid A through the particle collection vessel 210 (via its inlet 230 and outlet 240) and directs it out of its outlet mixed with the compressed air A’.

However, the apparatus 201 also includes a second vacuum generating unit 10b. This unit 10b is arranged in reverse in that its outlet is connected to the outlet 240 of the particle collection vessel 210 rather than its inlet.

The pipe 250, or other form of connection, from the outlet 240 of the particle collection vessel 210 still leads to the inlet of the first vacuum generating unit 10 but it now includes a branch 252 to the outlet of the second vacuum generating unit 10b. Furthermore, two

valves

253, 254 are located in the

pipes

251, 252 leading from the branch to the inlet of the first vacuum generating unit 10 and the outlet of the second generating unit 10b respectively.

The second vacuum generating unit 10b is powered by the source of compressed air 290 in the same way as the first vacuum generating unit 10. This flow of compressed air is controlled by a regulator 296 which is in turn operated by the controller 280.

To operate the apparatus 201 such that instead of air being pulled through the particle collection vessel 210 by the first vacuum generating unit 10, air is pushed through it from the second vacuum generating unit 10b, the valve 253 leading to the first vacuum generating unit 10 is closed and the valve 254 leading to the second vacuum generating unit 10b is opened.

At the same time the flow A’ of compressed air to the first vacuum generating unit 10 is stopped and the flow B’ to the second vacuum generating unit 10b is started.

In this way the first vacuum generating unit 10 ceases to pull air A or other fluid through the particle collection vessel 201 and instead air B is sucked in through the inlet of the second vacuum generating unit 10b and pushed into the outlet 240 of the particle collection vessel 210, such that a mixture of compressed air B’ and the air B sucked in moves through the particle collection vessel 210 from its outlet 240 to its inlet 230 in a reverse direction to that described with reference to Figure 2.

If this direction is then reversed again by supplying compressed air to the first vacuum generating unit 10 and stopping it to the second vacuum generating unit 10b (along with the opening and closing of the relevant valves 253, 254) then the initial direction may be reproduced again.

A continuous repetition of these two states or directions of flow may simulate breathing cycles to more closely mimic actual use by a person.

Although Figure 3 shows the two

vacuum generating devices

10, 10b in parallel it will be understood that they could be arranged in series with the same effect.

In Figure 3, the controller 280 is shown connected to the various items of equipment by

dotted lines

281, 282, 283, 284, 286, 287 288. These indicate control lines which may be electrical, mechanical, direct and/or indirect as will be understood by a person familiar with such technology.

In this regard, although a controller 280 is shown it is possible that the apparatus be controlled manually or semi-manually.

Figures 2 and 3 depict particle collection vessels of the type known as impactors. It is contemplated that these may be replaced or added to with other types of collection means such as impingers or dose collection tubes. More than one type of particle collector may be connected to the apparatus at one time.

Although shown as separate items the collection vessel and vacuum generating unit(s) may be integral with one another.

Claims

A particle collector apparatus, for use in testing medical devices which emit particulates, such as inhalers, comprising a collection vessel having an inlet, for connection with the device to be tested, and an outlet, and a first vacuum generating unit connected to the outlet, wherein the first vacuum generating unit is powered by movement of a first vacuum-forming fluid to produce a first at least partial vacuum thereby inducing a flow of a first sample fluid in a first direction through the collection vessel from the inlet to the outlet, wherein the collection vessel is an impactor or an impinger.
The apparatus of claim 1, wherein the first sample fluid is drawn through the collection vessel from the inlet to the outlet by a suction force induced by the first at least partial vacuum, and the apparatus is arranged such that this first sample fluid mixes with the first vacuum-forming fluid in the first vacuum generating unit.
The apparatus of either one of claims 1 and 2, wherein the first vacuum generating unit relies upon the Coander effect and/or Bernoulli principle in operation to produce the first at least partial vacuum.
The apparatus of any preceding claim, wherein the first vacuum-forming fluid is compressed air.
The apparatus of any preceding claim, including a controller arranged to monitor the flow rate of the first sample fluid exiting the collection vessel and variably adjust, as necessary, the pressure and/or volume flow rate of the first vacuum-forming fluid through the first vacuum generating unit so as to maintain the flow rate and/or pressure of the first sample fluid at a predetermined value.
The apparatus of any preceding claim, comprising a second vacuum generating unit powered by movement of a second vacuum-forming fluid to produce a second at least partial vacuum thereby inducing a flow of a second sample fluid in a second direction through the collection vessel, wherein the second direction is substantially opposite to the first direction.
The apparatus of claim 6, wherein the controller is arranged to monitor the flow rate of the second sample fluid entering the collection vessel and variably adjust, as necessary, the pressure and/or volume flow rate of fluid through the second vacuum generating unit so as to maintain the flow rate and/or pressure of the second sample fluid at a predetermined amount.
The apparatus of either one of claims 6, and 7 when dependent directly on claim 6, comprising one or more flow meters for measuring the rate of flow of the second sample fluid.
The apparatus of any one of claims 6 to 8, when dependent or indirectly directly on claim 6, comprising one or more pressure gauges for measuring the pressure of the second vacuum-forming fluid.
The apparatus of any preceding claim, comprising one or more flow meters for measuring the rate of flow of the first sample fluid.
The apparatus of any preceding claim, comprising one or more pressure gauges for measuring the pressure of the first vacuum-forming fluid.
The apparatus of any preceding claim, comprising an exhaust fluid trap for trapping the fluid exiting the collection vessel.
The apparatus of any preceding claim including an automatically controllable valve for controlling the pressure in the collection vessel such that a leak test is performable on the collection vessel.
The apparatus of claim 13, when directly or indirectly dependent on claim 5, wherein the controller is arranged to perform a leak test on the collection vessel.
The apparatus of any preceding claim including medical device holding and moving equipment for variously holding the exit of the medical device in front of the inlet of the collection vessel, activating the medical device to emit particulates, shaking the medical device, and removing the medical device away from the inlet of the collection vessel, wherein the medical device holding and moving equipment is arranged to cooperate with collection vessels having various inlet positions.
A method of collecting particles entrained in a first sample fluid comprising the steps of providing apparatus according to any one of claims 1 to 15, providing a source of particles in fluid connection with the inlet of the collection vessel, providing a first vacuum-forming fluid, controlling the flow of the first vacuum-forming fluid through the first vacuum generating unit thereby inducing a flow of a first sample fluid through the collection vessel thus sucking in particles from the source of particles.
The method of claim 16, further comprising the steps of providing a second vacuum generating unit according to claim 6, connecting it to the collection vessel, and controlling the first and second vacuum generating units to provide a flow of fluid through the collection vessel which alternates in direction thereby to simulate breathing.