PARTICULATE COLLECTION SYSTEM AND METHOD

Abstract

A particle concentrator system for the concentration of particulate material is described. The particle concentrator system comprises a prefilter module comprising a first inertial classifier configured to retain a flow in which particles smaller than a predetermined cut point size tend to segregate differentially; and a concentrator module comprising at least one second inertial classifier, and optionally more than one fluidly in series, configured to retain a flow in which particles larger than a predetermined cut point size tend to segregate differentially. The inertial classifiers are preferably virtual impactors. A gas sampler system, a gas sampler, concentrator and collection system, a method for the collection of a sample of aerosolised particulate material using such systems are also described.

Claims

1. A particle concentrator system for the concentration of particulate material comprising: a prefilter module comprising a first inertial classifier configured to receive an inlet gas flow comprising particulate material and configured to divide the inlet flow into a first outlet flow into which particles smaller than a predetermined cut point size tend to segregate differentially and a second outlet flow into which particles larger than a predetermined cut point size tend to segregate differentially, the predetermined cut point size being selected to be at a desired maximum particle size; a concentrator module comprising a second inertial classifier fluidly positioned to receive an inlet flow from the first outlet flow of the first inertial classifier and configured to divide the inlet flow into a first outlet flow into which particles smaller than a predetermined cut point size tend to segregate differentially and a second outlet flow into which particles larger than a predetermined cut point size tend to segregate differentially, the predetermined cut point size being selected to be at or below a desired minimum particle size; an outlet to output the second outlet flow.

2. A particle concentrator system in accordance with claim 1 wherein the concentrator module comprises at least one further inertial classifier, each such further inertial classifier successively fluidly positioned to receive an inlet flow from the second outlet flow of the immediately preceding inertial classifier and configured to divide the inlet flow into a first outlet flow into which particles smaller than a predetermined cut point size tend to segregate differentially and a second outlet flow into which particles larger than a predetermined cut point size tend to segregate differentially, the predetermined cut point size being selected to be at or below a desired minimum particle size; and an outlet to output the second outlet flow of the concentrator module.

3. A particle concentrator system in accordance with claim 2 wherein the concentrator module comprises exactly two inertial classifiers fluidly in series.

4. A particle concentrator system in accordance with claim 1 comprising a pre-filter module comprising a first inertial classifier stage and a concentrator module with at least a second inertial classifier stage and at least one further inertial classifier stage, wherein each stage may comprise multiple discrete fluidly parallel inertial classifiers.

5. A particle concentrator system in accordance with claim 1 wherein each inertial classifier is an impactor.

6. A particle concentrator system in accordance with claim 5 wherein each inertial classifier is a virtual impactor.

7. A particle concentrator system in accordance with claim 6 comprising: a prefilter module comprising a first virtual impactor configured to receive a gas flow comprising particulate material; a concentrator module comprising a second virtual impactor fluidly positioned to receive an inlet flow from the first outlet flow of the first virtual impactor; and at least one further virtual impactor, each such further virtual impactor successively fluidly positioned to receive an inlet flow from the second outlet flow of the immediately preceding virtual impactor; and an outlet to output the second outlet flow of the concentrator module.

8. A particle concentrator system in accordance with claim 7 comprising: a prefilter module comprising a first virtual impactor configured to receive a gas flow comprising particulate material and for example fluidly positioned to receive an inlet flow from the sampler inlet and configured to divide the inlet flow into a first, major outlet flow into which smaller particles tend to segregate differentially and a second, minor outlet flow into which larger particles tend to segregate differentially; a concentrator module comprising: a second virtual impactor fluidly positioned to receive an inlet flow from the first, major outlet flow of the first virtual impactor and configured to divide the inlet flow into a first, major outlet flow into which smaller particles tend to segregate differentially and a second, minor outlet flow into which larger particles tend to segregate differentially; a further virtual impactor fluidly positioned to receive an inlet flow from the second, minor outlet flow of the second virtual impactor and configured to divide the inlet flow into a first, major outlet flow into which smaller particles tend to segregate differentially and a second, minor outlet flow into which larger particles tend to segregate differentially; an outlet to output the second, minor outlet flow of the concentrator module.

9. A particle concentrator system in accordance with claim 6 wherein successive virtual impactors comprising the prefilter virtual impactor and the concentrator virtual impactor(s) form a planar array.

10. A particle concentrator system in accordance with claim 9 wherein the successive virtual impactors making up the planar array are compactly associated together in a planar formation extending fluidly from an inlet into a prefilter module at the edge of the planar formation to an outlet from the concentrator module towards the centre of the planar formation.

11. (canceled)

12. A particle concentrator system in accordance with claim 10 wherein the planar formation has a circular shape, wherein the successive virtual impactors making up the planar array are concentrically associated together in a planar formation extending fluidly from an inlet to a prefilter module at the edge of the circle to an outlet of the concentrator module towards the centre of the circle.

13. (canceled)

14. A particle concentrator system in accordance with claim 10 wherein the planar formation comprises a plurality of sectors extending fluidly from an inlet into a prefilter module at the edge of the planar formation to an outlet from the concentrator module towards the centre of the planar formation.

15. (canceled)

16. A particle concentrator system in accordance with claim 1 wherein the concentrator system comprises a planar formation with a circular shape divided into a plurality of fluidly discrete sectors angularly arrayed about the circumference, each sector comprising, successively in fluid series, the prefilter module and the concentrator module, extending fluidly from an inlet into a prefilter module at the circumferential edge of the planar formation to an outlet from the concentrator module towards the centre of the circle.

17-19. (canceled)

20. A particle concentrator system in accordance with claim 1 wherein successive inertial classifiers are sized to reflect the differential flow volumes, a downstream classifier being smaller than an upstream one.

21. A gas sampler system for the collection and concentration of particulate material comprising: a sampler inlet for example provided in a sampler inlet module to receive a gas flow comprising particulate material; a particle concentrator system in accordance with any preceding claim; wherein the prefilter module is fluidly positioned to receive an inlet flow from the sampler inlet.

22. A gas sampler, concentrator and collection system for the concentration of particulate material and collection of the same into a suitable buffer solution comprises: a system in accordance with claim 21; a collection module positioned fluidly to receive the output of the concentrator module and capture the particles into an aqueous liquid buffer.

23. A system in accordance with claim 22 wherein the collection module comprises a wet-wall cyclone.

24. A system in accordance with claim 23 wherein the collection module further comprises a misting chamber upstream of the wet-wall cyclone including a misting device configured to add water droplets to the output of the concentrator module.

25. A method for the collection of a sample of particulate material comprising: receiving an inlet gas flow comprising particulate material; causing the gas flow to pass through a prefilter module comprising a first inertial classifier fluidly positioned to receive the inlet flow and configured to divide the inlet flow into a first outlet flow into which smaller particles tend to segregate differentially and a second outlet flow into which larger particles tend to segregate differentially; causing the first outlet flow to pass through a second inertial classifier configured to divide the inlet flow into a first outlet flow into which smaller particles tend to segregate differentially and a second outlet flow into which larger particles tend to segregate differentially; optionally causing the second outlet flow of the second inertial classifier to pass through at least one further inertial classifier fluidly positioned to receive an inlet flow from the and configured to divide the inlet flow into a first outlet flow into which smaller particles tend to segregate differentially and a second outlet flow into which larger particles tend to segregate differentially.

26. The method of claim 25 wherein each inertial classifier is a virtual impactor, and the method comprises: receiving a gas flow comprising particulate material; causing the gas flow to pass through a prefilter module comprising a first virtual impactor; causing the first outlet flow of the first virtual impactor to pass through a second virtual impactor; causing the second outlet flow of the first virtual impactor to pass through at least one further virtual impactor; outputting the minor outlet flow of the second or further virtual impactor.

27. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0075] The invention will now be described by way of example only with reference to FIGS. 1 to 10 of the accompanying drawings, in which:

[0076] FIG. 1 is a schematic view of the principles of a sampling and collection system in accordance with an embodiment of the invention;

[0077] FIG. 2 shows in more detail a possible arrangement of pre-filter and concentrator virtual impactors for use with the sampling and collection system of FIG. 1;

[0078] FIGS. 3 and 4 illustrate the adaptation of a system in accordance with the invention for deployment in the field, for example mounted on a vehicle;

[0079] FIG. 5 shows a planar pre-filter and concentrator formation with an alternative arrangement of virtual impactors suitable for use in a sampling and collection system;

[0080] FIGS. 6 and 7 show alternative compact planar formation geometries of virtual impactors suitable for use with a sampling and collection system;

[0081] FIGS. 8 to 10 show an inlet module particularly adapted for use on a moving vehicle;

[0082] FIG. 11 shows an example collection module.

DETAILED DESCRIPTION

[0083] The concept of the invention in its broadest aspects is of a system and method for the collection of airborne and for example aerosolised particulate material, for example for the collection of an air sample. The concept of the invention in its extended aspect comprises the use of such an air sampling system and collection and method as part of a system and method for the analysis of such airborne particulate material.

[0084] An analysis system and method in accordance with an embodiment of the invention, and applying an air sampling and collection system and method in accordance with an embodiment of the invention, is described.

[0085] The invention finds particular applicability to the collection and optionally further the analysis of biological samples, and for example the collection of genetic material and optionally further the analysis of genetic material by sequencing, and the illustrated embodiment is configured for such collection and analysis by way of example.

[0086] FIG. 1 is a schematic illustration of an air sampler and particulate collector that includes a concentrator system in accordance with an embodiment of the invention.

[0087] The air sampler in the illustrated embodiment may be considered as comprising three sub-systems each with a different function. These are an inlet, a pre-filter and particulate concentrator, and a collector.

[0088] The particle size range of interest in the illustrated embodiment is 0.4 μm to 10 μm, the respirable range. Therefore, the air sampler technology must retain particles within that range.

[0089] A suitable inlet arrangement may be provided through which air may be drawn into the illustrated prefilter and concentrator. The inlet may include a physical filter upstream of the prefilter module to remove larger particles from the system altogether before they are drawn into the prefilter module, In an example case, the inlet filter stops particles of size greater than 2 mm getting into the pre-filter.

[0090] The inlet sub-system captures and channels air from the sensor's local environment to the concentrator and collector. In the illustrated FIG. 1 representation, a simple unidirectional opening into the pre-filter is shown. In practice, more structured inlet modules providing for the particular dynamics of collection in particular scenarios, such as those discussed below, are likely to be more appropriate.

[0091] The inlet may be structured to stops large debris entering the system. For example a physical inlet filter may be used. In the FIG. 1 embodiment a simple cover is envisaged to be mounted above the pre-filter. Around its circumference is a 2 mm fine wire mesh to allow air to enter but not larger particulates.

[0092] Some embodiments may rely on forced airflow to collect particles. In that case a vacuum pump is used to pull air through the sampler to maintain a pressure differential between the pre-filter and outlet. The vacuum pump remains on the clean side of the collector such that the pump remains uncontaminated and no particles of interest are lost on impellor blades. In a case where a system is mounted on a vehicle or the like, when the vehicle is in motion, air can be collected by using a duct that uses the inherent air flow generated by the moving vehicle.

[0093] There is a desire to maximise on the amount of air that is sampled within a 30 s period. As the limit of detection (sensitivity) for the sensor is estimated to be 0.1 PPL (target) or 0.5 PPL (threshold), the more air that is sampled in any period should result in a higher recovery and yield of pathogenic microbes.

[0094] This is the particular role of the ‘Pre-filter and Particle Concentrator’ which in the embodiment uses the series of virtual impactors shown.

[0095] The pre-filter and concentrator system comprises three successively arrayed virtual impactors of a generally conventional design, respectively being a pre-filter stage comprising a first virtual impactor configured to receive airborne particulate material, a first concentrator stage comprising a second virtual impactor fluidly positioned to receive an inlet flow from the major outlet flow of the first virtual impactor, and a second concentrator stage comprising a further virtual impactor fluidly positioned to receive an inlet flow from the minor outlet flow of the second virtual impactor, and is configured to output the minor outlet flow of the concentrator module to a collector.

[0096] The main advantages of virtual impactors for particle sizing and concentration can be summarised as follows: [0097] High collection efficiency for small particle sizes (bellow 1 mm) compared to conventional impactors and other sampling equipment. [0098] Operation at low pressure drop, leading to lower running costs and power consumption. [0099] Sharp cut-off characteristics (smaller amounts of particles around a cut-off point enter the next stage)

[0100] Using the same technology for both operations, (sizing particles and flow concentration), is most cost effective as the design and manufacturing is in principle the same. Successive progressively smaller stages are fluidly linked together in line.

[0101] The pre-filter and particulate concentrator sub-system serves to select a desired particle size range and concentrate the sample to increase the number of particles in a given volume of air. The pre-filter and particulate concentrator sub-module of the embodiment serves to select this particle size range and to concentrate it to a nominal design mode of concentrating particles within 2400 litres of air into 49 litres of air. This is intended to reduce the amount of time that is needed to collect enough genomic material to run the sequencer.

[0102] The pre-filter ensures that outside air enters the system and removes any particles above 10 μm. The concentrator increases the amount of biomolecules that are present in any given volume of air and the collector transfers them from their airborne phase into an aqueous phase. There are two collectors and they are used for 30 seconds every 60 seconds. After a 30 second collection period, a valve diverts air to the other collector and back again another 30 seconds later. This enables continuous collection of material.

[0103] In the example embodiment, the ‘Pre-Filter’ takes in contaminated air at a rate of 4800 l/min. The minor flow removes particles over 10 μm in size, at a flow rate of 480 l/min. The sub 10 μm particles continue onto the stage 1 concentrator at a flow rate of 4320 l/min.

[0104] Stage 1 of the concentrator receives the sub 10 μm particles from the ‘Pre-Filter’ stage. The major flow of stage 1, containing no particles flows at a rate of 3770 l/min. The sub 10 μm particles continue to ‘Stage 2’ at a flow rate of 550 l/min.

[0105] Stage 2 of the concentrator receives the sub 10 micron particles from ‘Stage 1’. The major flow of stage 2, containing no particles, flows at a rate of 453 l/min. The sub 10 μm particles exit through the minor flow of stage 2, stage 2 at a flow rate of 97 l/min. The particles exiting Stage 2 are channelled to the collector.

[0106] The collector sub-system captures the particles into a liquid buffer so that they can be further processed downstream.

[0107] In the embodiment two collectors are alternately used. The collectors preferably use a wet cyclone technology to capture the concentrated sample. The main downsides of a wet cyclone collector is the susceptibility of the buffer to evaporate. This leads to higher levels of losses. Another potential issue and cause of loss is the re-aerosolization of buffer/biological material. As a consequence, the system that has been designed to use a scrubbing mist to increase capture efficiencies by having the droplets agglomerating onto the particulates to increase their effective size, making it easier for them to be captured. The mist may be injected into the collector. Additionally or alternatively a scrubber mist may be injected into the first stage flow concentration virtual impactor.

[0108] An additional benefit of using this technique is that the mist continually replenishes the collection buffer. Any residue that may usually build up on the collector walls is continually washed.

[0109] It will be appreciated that these advantages accrue, and the concept of a scrubber mist is therefore applicable, across the range of possible collector and concentrator technologies, and not merely in the embodiment illustrated in FIG. 1.

[0110] FIG. 2 shows in more detail a possible arrangement of virtual impactor for use with the sampling and collection system of FIG. 1.

[0111] The design makes use of multiple flow channels comprising slits arranged in circular arcs instead of straight lines. The circular arrangement means that the impactor/particle filter can be mounted in-line within a circular duct. This avoids problems of changing from a circular inlet duct to a square impactor duct and back to a circular outlet. Moreover, with the pre-filter in the horizontal orientation and with it being circular, collection efficiencies may be less affected by the direction of air that passes over it.

[0112] The exhaust outlet channels are tapered according to the amount of air passing through them (i.e. bigger towards the outside of the device). The tapering of the outlets is intended to help obtain an even distribution of airspeed across the whole device, i.e. the same speed of air enters the outer slits as enters the inner slits.

[0113] Once collected in the wet cyclone of FIG. 1, the buffer is collected in a collection vessel before being pumped into the ‘wet lab’ process.

[0114] The concept of the invention in its extended aspect includes elements of the ‘wet lab’ process.

[0115] Example elements of this ‘wet lab’ process, and of subsequent data processing, include, without limitation, the following.

[0116] Cell Concentrator

[0117] Once the sample has been collected and the particulates are suspended in a liquid buffer, it is then injected into the first module of the pipeline, the cell concentrator. Given the volume of liquid that is required to agglomerate the particulates present in 2400 litres of air, nominally between 10 and 45 mL depending on the collection technology. Two main technologies were identified as suitable to be implemented into the biosensing system.

[0118] The first utilises filters of sub-micron pore size to retain biomolecules whilst letting water pass through. It is a very well established methodology, commonly used in laboratories.

[0119] The second uses Dielectrophoresis (DEP)-based cell capture, which utilises metal electrodes and electric fields to capture biomolecules. DEP is also very well established for specifically capturing biomolecules (i.e. one specific type out of a mixed population) suspended in a liquid medium, however it has not commonly been used or developed to handle a metagenomic sample to capture the entire range of molecules within it. Its attractiveness comes from being automation-friendly, its low cost of fabrication and utilisation, which doesn't require consumables or complex elution procedures, and that it can potentially be reused indefinitely. Furthermore, DEP can be fine-tuned to target bacteria, viruses, DNA and RNA, making implementation of a metagenomic pipeline theoretically easier.

[0120] Analysis of Liquid

[0121] Following the high concentration of biomolecules in the liquid buffer, there are numerous techniques to analyse for on the presence of microbes of interest. Such techniques can be used to report the presence, or lack of, of target items.

[0122] As it is collected, data may be reported to a central system for example over a distributed network. In preferred embodiments, the system and method of the invention is adapted to be performed in the field using portable apparatus, and in particular using vehicle mounted apparatus. Multiple such portable apparatus distributed across an area such as an urban area and connected to a control centre for example by a distributed network might provide an effective system for the real time sensing of airborne biohazards and other hazards.

[0123] A system to be used in such an application might for example have the system components compactly associated with together in portable manner, and for example adapted to be mounted on a vehicle.

[0124] An embodiment of a compact and portable sampler suitable for deployment in the field and for example for vehicle mounting is shown in FIG. 3 and a schematic of a more complete modular system is in FIG. 4.

[0125] The air sampler module 1 contains the following sub-modules: Air inlet; Pre-filter; Airborne particulate concentration; Collector. In use on a vehicle, the air sampler module is roof-mounted to maximise sample collection, and is connected via an umbilical connection to an analysis module 2 and an automation hardware data processing module 3. These last two may be protected in the centre of vehicle structure, convenient for maintenance access. A ruggedized chassis module may house the analysis cartridge and automation hardware and data processing module.

[0126] The analysis cartridge module contains the following hardware sub-modules: Cell concentrator; Bio sensor; Reagent storage.

[0127] The automation hardware and data processing module contains the following sub-modules: Fluidic hardware such as automated syringe pumps, valves and control gear Power supplies and other power management systems Computer and associated data collection devices

[0128] In the embodiment illustrated in FIG. 2, the successive virtual impactors are arrayed vertically, with generally longitudinal flow paths between them. Other arrangements may be considered without departing from the principles of the invention that the prefilter and concentrator modules comprise, and the prefilter and concentrator functions are provided by, successive inertial classifiers, for example being successive virtual impactors. For example, inertial classifiers in a radial array, or hybrid of radial and longitudinal or other arrangement may be considered.

[0129] Moreover, in the embodiment illustrated in FIG. 2, the successive virtual impactors are illustrated as clearly discrete modules performing the respective prefilter and concentrator stage 1 and stage 2 functions. A single compound module adapted to include multiple stages is also encompassed by the principles of the invention.

[0130] Alternative embodiments with adaptations as above for possible more compact operation are shown in FIGS. 5 and 6.

[0131] FIG. 5 shows an example of such a compact concentrator system.

[0132] Fundamentally, the fluid processes in this compact concentrator system, and fluid processes and structures in the successive impactor stages, are equivalent to those of the more conventional virtual impactors illustrated in FIG. 2. As in FIG. 2 the system has a prefilter stage comprising a first virtual impactor configured to receive airborne particulate material, a first concentrator stage comprising a second virtual impactor fluidly positioned to receive an inlet flow from the major outlet flow of the first virtual impactor, and a second concentrator stage comprising a further virtual impactor fluidly positioned to receive an inlet flow from the minor outlet flow of the second virtual impactor, and is configured to output the minor outlet flow of the concentrator module to a collector.

[0133] However the example compact concentrator system illustrates a number of general design principles each of which may alone or in combination be advantageous in a pre-filter and concentrator of the invention in some operational situations, for example where compactness is required and/or for deployment in the field, including:

the development of a planar array of successive impactors;
the combination of the pre-filter and inertial classifier function into a single compact pre-filter and concentrator unit or segment;
the provision of a plurality of these units or segments fluidly in parallel;
the provision of a plurality of these units or segments arranged compactly together radially.
the provision of a system with 360 degree inlet flow.

[0134] As can be seen in FIG. 5A the pre-filter and concentrator formation is conformed as a planar circular disc with 12 fluidly discrete units comprising arrangements of prefilter, first concentrator and second concentrator, each comprising a 30 degree segment of the disc. The virtual impactors making up the pre-filter stage are outermost, the virtual impactors making up the first concentrator stage are next inward, and the virtual impactors making up the second concentrator stage are closest to the centre.

[0135] The discs are themselves a sandwich of three layers to create the channels that route the exhausts away from each individual virtual impactor. The wall sections help reduce the turbulence in the flow between the stages as well as provide a means of getting the exhaust air from the top of the concentrator ring to the bottom.

[0136] FIG. 5B shows the flow pattern through an individual segment and through the virtual impactors making up the successive stages therein.

[0137] In the illustrated embodiment, the segment fluidly discrete, with the prefilter stage fluidly connected in series to first and second successive concentrator stages. Other more complex arrangements could be readily envisaged without departing from the principles of the invention in which respective stages are divided different numbers of sectors and/or different numbers of impactors in a sector are provided at each stage, with more complex mixed serial and parallel fluid connections between them.

[0138] FIGS. 6 and 7 show in simple schematic alternative geometries of compact planar pre-filter and concentrator formations again made up of multiple pre-filter and concentrator units or segments and also how the formation may be incorporated into a more complete collection system.

[0139] FIG. 6 shows an alternative square planar geometry pre-filter and concentrator formation, with the illustrated embodiment containing four units or segments covering four quadrants of the sampler, in a suitable enclosure.

[0140] This embodiment contains enclosure 21, four impactors 22, manifolds between the impactors 23 and a central collector 24, fans and ducting 25 and a pumping mechanism 26.

[0141] Other preferred features or advantages offered by these more compact arrangements embodiment include:

the inlet is built into the enclosure;
the arrangement maximises space—air collection to volume ratio;
manifolds separate each impactor, serving both sides;
enables removal of much ducting, valving and throttling to balance flow;
the size of the overall unit may be reduced significantly.

[0142] FIG. 7 illustrates schematically some possible further alternative features for such a compact sampler.

[0143] The key design difference that can be seen in the FIG. 6 embodiment is that the impactors 32 are curved and placed inside a circular inlet and enclosure 31. The individual impactors are separated by suitably curved manifolds 33, with no dead space in between. The impactors and manifolds allow collection of the air at a central, single collector 34 which can then output to the latter stages of the air sampler. The remaining downstream components of the sampler are in the housing 35.

[0144] Advantages of the curved impactor design include that the air sees the same cross sectional area (the system is omnidirectional) and that a large surface area is created in a compact design.

[0145] The simple inlet presented in FIG. 3 is not necessarily optimized for use in all scenarios on a moving vehicle, and alternative optimizations are discussed with reference to FIGS. 8 to 10.

[0146] The principal challenge is to make sure that there is no pressure differential into the air sampler with differing wind speeds/directions.

[0147] Significant challenges have had to be overcome to keep the full 360-degree collection capability as well as direct as much of the PM.sub.10 particle matter into the air collector without significant particulate deposits on the inside of the inlet. Initial investigations showed that a simple dome with a slit was capable of preventing the larger particulate matter from being drawn into the air collector without affecting the transfer of PM.sub.10. However, when an airflow was introduced representative of the airflow over a moving vehicle, the simulation showed that the airflow caused a significant pressure difference between the leading and trailing faces of the collector. The pressure difference was significant enough to over-drive the concentrators on the leading face and suck air out through the collectors on the trailing faces. This approach is not always capable of normalizing the airflow around the air collector sufficiently to allow it to function correctly.

[0148] An alternative inlet module design giving improved functionality having regard to such configurations, and particularly adapted for use with the example compact unit of FIG. 5, is shown in FIGS. 8 and 9.

[0149] The inlet uses six inlet scoops to create a tangential air flow around the outside of the air collector to normalise the flow through all twelve of the pre-filter and concentrator segments. FIG. 8 shows a cross section view of the new inlet design with the six scoops located in the top of the dome over the air collector (housing only shown) with an aerodynamic cowling to cover the exhaust pipes.

[0150] The inlet scoops produce a cyclic airflow in the chamber above the air collector which moves down and out to the air collector inlets. This approach both normalises the pressure distribution around the air collector as well as reduces turbulence and particle deposition on the air collector and the inside of the inlet. In a stationary setting the air collector draws the air in through all six of the inlet scoops and collects a true full 360-degree sample. As the airflow around the inlet is increased the air that makes it into the inlet becomes increasingly biased towards the scoops on the leading face, but the air collector is still able to function correctly and sample the air inside the inlet using all segments.

[0151] FIG. 9 shows the directional bias created by the airflow around the inlet. It can be seen that at low speeds (≤4 m/s) there is a maximum of 26% reduction and 23% increase in the flow through the scoops compared to when stationary. At these low speeds the inlet is more biased towards the left with a lower mass flow rate through the 2 right scoops. Despite this bias it is still capable of collecting a 360-degree sample with 26% of the sample coming from the right (scoops 2 and 3) and 39% coming from the left (scoops 5 and 6). At higher speeds 8 m/s) the bias is more towards the front left and rear with the maximum mass flow rate reduction of 56% (compared to stationary) being observed on the right. At these higher speeds the inlet still collects from all directions with 19% of the sample coming from the right and 36% from the left. At high speed (14 m/s) the sample is biased to the front and rear as air has just started to be drawn out of the side scoops. Despite the reversed flow in two of the scoops the inlet still collects 9% of the sample from the right and 21% from the left. It is possible that changing the direction of the airflow by about 15-degrees may significantly change the degree of the directional bias however this needs further investigation. The current design favours the left-hand side when presented with an airflow however this could be used to reduce the amount of vehicle emissions collected. By changing the direction of the scoops this bias could be swapped to the right-hand side (for left hand drive vehicles). On busy streets a larger proportion of the sample could be collected from the side with less traffic resulting in less deposition of material and less non-biological matter in the sample.

[0152] Investigations into particle transfer efficiency have shown that in stationary conditions the current design should achieve a 96.1% transfer efficiency for all PM.sub.10 particulate, which increases up to 99.5% for PM.sub.25, from the environment to the air collector. As the airflow is increased to 14 m/s (31 miles per hour) the PM.sub.10 transfer efficiency drops to 63.4% and the PM.sub.2.5 transfer efficiency drops to 88.5%.

[0153] It is important to note that the transfer efficiency is from the surrounding environment external to the inlet to the inlet of the prefilter of the air collector. This does not mean that all of the PM.sub.10 particles that do not make it into the air collector are deposited inside the inlet. It is far more likely that the majority of the lost particles do not enter the inlet scoops as they have a small stokes number so are caught up in the flow around the outside of the inlet dome. FIG. 10 shows CFD results of PM.sub.10 mass concentration in an 8 m/s airflow from left to right.

[0154] Thus, the inlet arrangement of the example design illustrated with respect to FIGS. 8 to 10 is admirably adapted for use in a system in accordance with the invention deployed on a moving vehicle, in particular dealing with the problems posed by pressure differential into the air sampler with differing wind speeds/directions, and the desire to achieve a 360-degree collection capability as well as direct as much of the PM.sub.10 particle matter into the air collector without significant particulate deposits on the inside of the inlet.

[0155] FIG. 11 shows in more detail a possible arrangement of collector for use with the sampling and collection system of FIG. 1 or any other suitably compatible sampling and collection system in accordance with the principles of the invention.

[0156] The example collector comprises a misting chamber and a wet-wall cyclone.

[0157] The misting chamber is used to create water droplets in the air stream. The embodiment uses an ultrasonic mister. The ultrasonic mister is found to produce a more uniform mist of water droplets with a sufficiently small stokes number that they follow the airflow. An inlet funnel is used upstream of the misting chamber to reduce the amount of water build up in the ducting to the cyclone inlets by reducing the likelihood of the droplets settling or impacting on the walls of the ducting. For use outdoors, a cover for the inlet is added to prevent large particulate matter from entering the system as well as any other debris such as leaves, and insects.

[0158] The ultrasonic mister sits in the misting chamber and is submerged in water. When powered the mister produces water droplets in the range of 2 μm to 15 μm which drift out of vent holes in the side of the misting chamber into the inlet funnel. Once in the inlet funnel the water droplets mix with the air that is being drawn through the apparatus and are drawn into the cyclone with the airflow through the inlet funnel.

[0159] A vacuum pump is used to draw the air through the apparatus with a flow meter and a flow control valve to allow the flow rate to be set to 98l/min which the cyclone was designed to operate at. The air is drawn into the apparatus through the gap between the inlet cover and the top of the inlet funnel. The main function of the inlet cover is to prevent unwanted material from entering the inlet funnel, it will also prevent larger particulate matter such as dust from entering the apparatus as it will not be able to follow the airstream due to the low velocity of the airflow and the larger mass of the particles producing a large stokes number.

[0160] The air is drawn through the inlet funnel, where it mixes with the water droplets from the misting chamber, and into the cyclone. The air is drawn out of the cyclone and through the catch pot where again due to the size of the water droplets they impact on the bottom of the catch pot and are collected. The air is then drawn on through the flow control valve, flow meter and onto the vacuum pump where it is vented back to atmosphere. The liquid with any captured particulate matter that is separated from the airflow drains out of the bottom of the cyclone and collects in the collection pot.

[0161] The particulate sample from a suitably compatible prefilter and concentrator system such as one of the examples illustrated is thus effectively collected into an aqueous medium ready for further processing and for example analysis. This may for example be via an in-line system such as described by way of example above. Thus, the collector of FIG. 11 is an example of a collection module suitable for use with and fluidly connected to a suitably compatible prefilter and concentrator system and/or a suitably compatible analysis system.