GB2633599A

GB2633599A - Detector inlet apparatus and method

Info

Publication number: GB2633599A
Application number: GB2314061.9A
Authority: GB
Inventors: Clark Alastair; Atkinson Jonathan; Parker Alexander
Original assignee: Smiths Detection Watford Ltd
Current assignee: Smiths Detection Watford Ltd
Priority date: 2023-09-14
Filing date: 2023-09-14
Publication date: 2025-03-19
Also published as: GB202314061D0; WO2025056908A1

Abstract

An inlet apparatus for detection system 302 comprises inlet 102 and trap 118. The inlet receives a flow of test air and has heater 108 to vaporise an aerosol carried by the air for sampling. The trap collects aerosols from the air and vaporises collected aerosol for sampling. In an aspect, the inlet apparatus provides the air flow to the heater, and to the trap for collecting aerosols while air flow is being provided to the heater. In aspects, the inlet operates in two modes. In the first mode, the heater vaporises aerosols carried by a first portion of the air flow, and aerosols carried by a second portion of the air flow are collected on the trap. In the second mode, aerosols collected on the trap are vaporised. The heater may be in first flow path 108 and the trap in second flow path 110. Flow provider 114 may move the first portion of air flow from the heater past sampling port 122; flow provider 116 may move the second portion past the trap.

Description

Detector inlet apparatus and method The present disclosure relates to detection methods and inlet apparatus for detectors, and more particularly to methods and inlet apparatus for obtaining samples for detectors, still more particularly to methods and inlet apparatus for providing vaporised aerosols to a detector. These methods and apparatus may find particular application in spectrometry, for example ion mobility spectrometry and mass spectrometry.

Detectors, for example some types of ion mobility spectrometers, can operate by "inhaling" io a stream of gaseous fluid, such as air, into a detector inlet and sampling that air with an analytical apparatus to detect substances of interest. That inhaled stream of air can be sampled from the detector inlet using a sampling port such as a pinhole, capillary or membrane inlet.

Some analytical apparatus and particularly some ion mobility spectrometers are adapted for the analysis of vapours, and of gases. Such analytical apparatus may be configured to detect substances of interest, such as narcotics, explosives, and chemical warfare agents. The reliability and ability of such detectors to detect any significant quantity of such agents may therefore be a significant issue. Some substances of interest may comprise aerosols.

By contrast with a vapour or gas, an aerosol comprises fine particles of solid or liquid suspended in a gas. Where the substance has a low vapour pressure, an ion mobility spectrometer may be unable to detect particles of that substance in an aerosol without vaporisation of the aerosol.

Aerosols can be collected on a pre-concentrator for subsequent desorption and analysis.

However, this requires a time delay between sampling from an environment to be tested and receiving the results of the analysis.

Aspects and embodiments of the present disclosure aim to address the above technical 30 problems.

Summary

Embodiments of the disclosure relate to inlet apparatus for detection systems, for providing samples to an analytical apparatus for detecting a substance of interest.

Detectors such as mass spectrometers and ion mobility spectrometers may be configured to ionise a vapour, and then to analyse the ions generated from that vapour to detect substances of interest. Such detectors may be configured to inhale a flow of gaseous fluid from an environment to be tested, and then to take samples from this flow. The samples can then be tested to detect the presence of substances of interest. The gaseous fluid may comprise gas, such as air, vapour and aerosols, for example solid or liquid particles suspended in the gaseous fluid.

An analytical apparatus configured to analyse vapour samples can analyse vapours io present in the environment being sampled from directly. However, aerosols in the environment may need to be vaporised by heating an aerosol-containing flow of air to facilitate satisfactory analysis of the vaporised aerosol.

Aerosols can be vaporised in a flow of air as it passes from the environment to the detector, such as by a heater disposed in the inlet of a detector in the path of a sample drawn into an inlet of the detector. This can permit live monitoring of aerosols at the same time as vapour, without the need to preconcentrate the aerosols and desorb for analysis. However, where an aerosol is only present in low concentration, and particularly where aerosol particles are present in low number density, it can be difficult to reliably detect the small quantities of such aerosols due to insufficient concentration or inherent inability to synchronise aerosol vaporisation with an unknown time of arrival of low number density aerosol particles. Aerosols at low concentration may be collected on a trap until sufficient quantities are present for analysis. However, in doing this, live monitoring capability for detecting aerosols present in higher concentrations is not possible. Similarly, when a heater in the inlet of a detection apparatus is used to vaporise aerosols entering the inlet, this permits live monitoring of aerosols, however low concentration aerosols are vaporised without being present in sufficient concentrations for reliable detection, and as these low concentration aerosols have been vaporised, collection on an aerosol trap is not possible.

Embodiments of the disclosure aim to address such problems by controlling flow in the inlet of a detector to vaporise aerosols entering the inlet for analysis, to allow live analysis of aerosols in a flow of air to be tested, whilst also collecting aerosols on a trap to permit the collection and subsequent analysis of low concentration aerosols in the flow of air. Thus, live monitoring of vapour and aerosols may be carried out at the same time as providing trapping for the detection of low concentration aerosols. In this way, a single detection apparatus can provide low concentration aerosol analysis without sacrificing live detection capabilities for higher concentration aerosols and vapours.

Aspects of the disclosure are set out in the independent claims and optional features are set out in the dependent claims. Aspects of the disclosure may be provided in conjunction with each other, and features of one aspect may be applied to other aspects.

Disclosed herein are two particular aspects relating to configurations of an inlet apparatus configured to address the technical problems discussed.

One aspect provides an inlet apparatus for a detection system, the apparatus comprising: an inlet for receiving a flow of air to be tested, the inlet comprising a first heater configured to vaporise an aerosol carried by the air for sampling by an analytical apparatus; a trap configured to collect aerosols from the flow of air and to vaporise collected aerosols for sampling by the analytical apparatus; a first flow path comprising the first heater and one or more sampling ports downstream from the first heater through which the analytical apparatus can obtain samples from the inlet; a second flow path comprising the trap, is configured to provide the flow of air to be tested: a first flow provider for moving a first portion of the flow of air along the first flow path from the first heater past the one or more sampling ports; and a second flow provider for moving a second portion of the flow of air along the second flow path past the trap.

As will be appreciated, the first flow path is separate from the second flow path. In this way, the inlet apparatus permits aerosols to be collected on the trap by diverting the second portion of the flow of air into a second flow path, whilst also allowing aerosols in the first portion of the flow of air to be vaporised and, together with vapours present in the flow of air, passed for analysis to an analytical apparatus. Thus, low concentration aerosols can be collected whilst simultaneously allowing live analysis of aerosols and vapours in the flow of air to be tested.

Another aspect provides an inlet apparatus for a detection system, the apparatus comprising: an inlet for receiving a flow of air to be tested, the inlet comprising a first heater configured to vaporise an aerosol carried by the air for sampling by an analytical apparatus; a trap configured to collect aerosols from the flow of air and to vaporise collected aerosols for sampling by the analytical apparatus; a flow path having a first end configured to receive the flow of air to be tested, and a second end; one or more sampling ports through which the analytical apparatus can obtain samples from the inlet, the one or more sampling ports arranged between the first heater and the second end so that aerosols flowing through the inlet from the first end to the second end can be vaporised by the first heater and provided to the one or more sampling ports; wherein the trap is arranged between the one or more sampling ports and the second end so that aerosols carried by the flow of air past the first heater and past the one or more sampling ports are collected on the trap.

In such a configuration, aerosols may be vaporised for analysis as they pass the first heater for sampling via the one or more sampling ports, and when the heater is not operated aerosols can pass the heater and the one or more sampling ports for collection on the trap. Thus, by operating the heater intermittently, aerosols can be analysed as they enter the inlet in addition to providing aerosols to the trap for collection to permit the detection of low concentration aerosols.

Nonetheless, it will be appreciated that the concept to which the present disclosure is directed may generally be implemented in a number of different ways in addition to these particular configurations.

Thus, in an aspect there is provided an inlet apparatus for a detection system, the apparatus comprising: an inlet for receiving a flow of air to be tested, the inlet comprising a first heater configured to vaporise an aerosol carried by the air for sampling by an analytical apparatus; a trap configured to collect aerosols from the flow of air and to vaporise collected aerosols for sampling by the analytical apparatus; wherein the inlet apparatus is configured to provide the flow of air to be tested: (i) to the first heater to enable vaporisation of aerosols in the flow of air for sampling by the analytical apparatus, and (ii) to the trap to collect aerosols on the trap while the flow of air is being provided to the first heater.

As will be appreciated, providing the flow of air to be tested to a heater for vaporising the aerosol as it passes through the inlet, whilst also providing the flow of air to a trap, can allow live analysis of aerosols in the environment by vaporising aerosols, whilst also providing for the collection of aerosols on a trap to permit the detection of low concentration aerosols that may not be reliably detected by in-line vaporisation as they enter the inlet. In this way, low concentration aerosols may be collected to permit reliable analysis without inhibiting the detection of aerosols comprising substances of interest in the time period in which low concentration aerosols are collected.

The inlet apparatus may be configured to divert a portion of the flow of air to be tested into a second flow path so that aerosols can be collected in the second flow path whilst aerosols are simultaneously permitted to pass along a first flow path in which aerosols can be vaporised as they pass the first heater.

Thus, in a preferred embodiment the inlet comprises: a first flow path comprising the first heater and one or more sampling ports downstream from the first heater through which the analytical apparatus can obtain samples from the inlet; a second flow path comprising the trap; a first flow provider for moving a first portion of the flow of air along the first flow path from the first heater past the one or more sampling ports; and a second flow provider for moving a second portion of the flow of air along the second flow path past the trap. As will be appreciated, "downstream" refers to the direction along the first flow path from the first heater to the one or more sampling ports, and similarly "upstream" refers to the direction along the first flow path from the one or more sampling ports to the first heater.

The second flow path can extend from the first flow path upstream of the one or more sampling ports. For example, the inlet may comprise a common inlet portion, configured to receive the flow of air to be tested, wherein the common inlet portion divides into the first flow path and the second flow path upstream of the one or more sampling ports. The first flow path may comprise a continuation of the common inlet, while the second flow path extends from the side of the first flow path, for example the inlet may have a constant cross-sectional area between the common inlet and the first flow path.

In general, where a flow path is referred to, this may suitably comprise a conduit having one or more walls configured to contain a flow within the conduit in order to direct the flow along the flow path, for example wherein the flow path is defined by the one or more walls of the conduit. Thus, a conduit may comprise an enclosed passageway for directing and containing flow travelling along a given flow path.

The first flow path may be defined by a first conduit configured to direct the first portion of the flow of air past the first heater then past the one or more sampling ports, the one or io more sampling ports configured to provide samples through a wall of the first conduit to the analytical apparatus.

Thus, the inlet may in general suitably comprise one or more sampling ports through which the analytical apparatus can be configured to obtain samples from the inlet. For example, the one or more sampling ports may be independently selected from a pinhole inlet, a capillary inlet or a membrane inlet. The analytical apparatus may be configured to obtain samples from the inlet in any suitable way, for example by pulsing a sampler (such as a pump) to draw samples from the inlet through the one or more sampling ports.

The second flow path may be defined by a second conduit that splits from the first conduit at a junction upstream of the one or more sampling pods, wherein the trap is disposed at the junction of the first and second conduits to collect aerosols present in the second portion of the flow of air entering the second conduit whilst permitting aerosols in the first portion of the flow of air to pass along the first conduit.

The second flow path may be separated from the first flow path by the trap. For example, the trap may extend across an entrance to the second flow path from the first flow path so that aerosols entering the second flow path must pass through the trap.

Suitably, the trap is arranged so that when then second flow provider is off, or when the second flow provider provides a reverse flow from the trap into the first flow path, vaporised aerosols vaporised from the trap can enter the first flow path for sampling by the one or more sampling ports. For example, the trap may be located in the second flow path adjacent to the first flow path so that, in the absence of a flow being provided from the first flow path into the second flow path, vaporised aerosols from the trap diffuse into the first flow path and can be carried along the first flow path to the one or more sampling inlets.

The configuration of the trap in the second flow path allows aerosol materials to be collected on an upstream side of the trap, for example such that aerosols are collected on a side of the trap that faces the first flow path. Thus, when aerosol materials are vaporised from the trap, they are already concentrated on the side of the trap closest to the one or more sampling ports, which may assist the provision of vaporised aerosol material from the trap into the first flow path and to the one or more sampling ports.

The first heater may be arranged in the first flow path downstream of the second flow path, for example downstream of an entrance to the second flow path (e.g. the junction), so that the second portion of the flow of air is provided to the trap without passing the first heater. Such a configuration allows the first heater to be operated without interfering with the collection of aerosols on the trap. In embodiments, the first heater may instead be arranged upstream of the entrance to the second flow path, and the first heater operable in a pulsed mode to intermittently provide heating. In this way, when the heater is off, aerosols may pass unvaporised for collection on the trap. Where the first heater is operated in a pulsed mode, the analytical apparatus can be configured to synchronise sampling of vaporised aerosols through the one or more sampling ports with operation of the first heater in order to provide vaporised aerosols from the first heater to the analytical apparatus.

The inlet apparatus may be operable in a first mode in which the first heater is operated to vaporise aerosols carried by the first portion of the flow of air for sampling by the analytical apparatus, and in which aerosols carried by the second portion of the flow of air are collected on the trap; and in a second mode in which aerosols collected on the trap are vaporised for sampling by the analytical apparatus.

In the first mode the first flow provider and the second flow provider may be operable at the same time to provide the first portion of the flow of air along the first flow path and the second portion of the flow of air along the second flow path. Thus, in the first mode, both the first and second flow provider are operated simultaneously to divide the flow of air to be tested into the first portion that passes along the first flow path, and the second portion that passes along the second flow path.

In the second mode, the inlet apparatus may be operable so that when the second flow provider is off or is operated in reverse, collected aerosols vaporised from the trap enter the first flow path and are provided by the first flow provider to the one or more sampling ports. As discussed, in the second mode, vapour desorbed from the trap may enter the first flow path by diffusion, for example when the second flow provider is off, to be carried to the one or more sampling inlets along the first flow path by operation of the first flow provider. Alternatively, in the second mode, the second flow provider may be operated to provide a reverse flow along the second flow path so that a flow is provided along the io second flow path, through the trap into the first flow path and to the one or more sampling ports.

A flow provider as referred to herein, for example the first flow provider or the second flow provider, may in general be provided by a pump, or a fan or any other suitable device for providing a flow of air through the inlet along a given flow path.

In a further embodiment, the inlet apparatus may be configured to pass the flow of air to be tested along a common flow path, for example a single conduit or enclosed passageway. Such a configuration may therefore be provided as an alternative to a configuration in which the flow of air to be tested is separated into first and second flow paths as described previously.

Thus, in another preferred embodiment the inlet defines a flow path having a first end and a second end the first end configured to receive the flow of air to be tested, the inlet comprising: one or more sampling ports through which the analytical apparatus can obtain samples from the inlet, the one or more sampling ports arranged between the first heater and the second end so that aerosols flowing through the inlet from the first end to the second end can be vaporised by the first heater and provided to the one or more sampling ports; wherein the trap is arranged between the one or more sampling ports and the second end so that aerosols carried by the flow of air past the first heater and past the one or more sampling ports are collected on the trap.

It will be appreciated that various elements of the inlet apparatus may nonetheless be as defined previously herein, for example with reference to conduits and flow paths and flow providers as described previously.

The inlet may suitably comprise a conduit configured to contain and direct the flow of air to be tested along the flow path.

The inlet apparatus may comprise a flow provider operable in a first mode to provide a first flow through the inlet from the first end to the second end, the flow provider operable in a second mode to provide a second flow through the inlet from the second end to the first end. In embodiments, the flow provider may comprise a first flow provider operable to provide the first flow through the inlet from the first end to the second end and a second flow provider operable to provide the second flow through the inlet from the second end to the first end. Alternatively, the flow provider may comprise a single flow provider configured to provide both the first flow and the second flow, for example wherein the flow provider is operable to provide flow bidirectionally, e.g. in a first direction as well as in a reverse direction.

The first heater is suitably operable in the first mode to provide intermittent heating, for example the first heater may be operable in a pulsed mode to intermittently provide heating, so as to allow aerosols in the first portion to pass the first heater unvaporised for collection on the trap. In the second mode, the trap is suitably operable to vaporise collected aerosols to be carried by the second flow for sampling by the analytical apparatus through the one or more sampling pods.

Thus, in the first mode the inlet apparatus is configured to intermittently operate the first heater to provide vaporised aerosols for sampling by the analytical apparatus, whilst also, when the first heater is off (for example between each pulse in which the first heater is operated), collecting aerosols on the trap that pass the first heater unvaporised.

As will be appreciated, as the trap is arranged between the one or more sampling ports and the second end, the second portion of the flow of air that provides aerosols to the trap arrives at an upstream side of the trap closest to the one or more sampling ports. In this way, aerosols collected on the trap are collected on a side of the trap that faces the one or more sampling ports, which may enhance the proportion of aerosols reaching the one or more sampling pods for sampling as the vaporised aerosols from the trap do not need to pass through the trap structure to arrive at the one or more sampling ports.

In general, where a heater is referred to this may comprise one or more separate heating means or a single means. For example, the heater may comprise a conductor, for example one or more elongate conductors such as a wire which may be arranged to be heated by resistive heating. The elongate conductors may comprise metal. A heater may be arranged as a grid or mesh to provide an obstacle in a flow path so that air flowing through that flow path flows through or around the heater. In general a heater, such as the first heater, preferably comprises wire or an array of elongate conductors arranged in a flow path in the path of the flow of air so that the flow of air must pass the wire or elongate conductors to reach the analytical apparatus.

io For example, the first heater preferably comprises conductors arranged across the inlet so that the flow of air to be tested passes between the conductors, for example wherein the first heater comprises an array of elongate conductors or wires extending across the inlet, for example a grid or an array of parallel elongate conductors. The elongate conductors may extend across a flow path from one wall of a conduit defining the flow path to an opposing wall of the conduit. The wires or elongate conductors may be produced by any suitable means, including by etching a metal substrate to provide the elongate conductors of the first heater.

The first heater may be arranged within the inlet or at least partially within it, for example one or more internal walls of the inlet may comprise the first heater. As will be appreciated, the first heater is suitably configured so as to vaporise aerosols passing the first heater along a respective flow path in which the heater is arranged.

In general, the first heater may comprise an array of elongate conductors (such as wire), for example parallel conductors, or an array of elongate conductors that follow a curved or winding path (e.g. a sinuous path) across the inlet. In preferred embodiments, the first heater may be configured to permit flow to pass the first heater whilst minimising capture of aerosols and vapours on the heater. The first heater may comprise elongate conductors, such as resistively heated wire, arranged across the inlet in the path of flow through the inlet (e.g. extending across the inlet perpendicular to the direction of flow through the inlet). The first heater may comprise an array of elongate conductors arranged across the inlet, for example an array of elongate conductors that may be arranged in a plane perpendicular to the direction of flow through the inlet. The thickness of the conductors (e.g. wires) and the gaps between conductors may be selected so as to minimise capture of aerosols on the first heater. The first heater may comprise more than one array of conductors, such as more than one array of conductors arranged in corresponding planes offset from each other in the flow direction. In other embodiments, the first heater may comprise a knitted structure, such as a wad or tangle of wire. One example of such a structure comprises a knitted mesh of wire such as Knitmesh (RTM).

The first heater structure may be arranged so that the wire occupies less than 80% of its volume, in some examples less than 60%, in some examples less than 40%, in some examples less than 20% of the volume is occupied by the conductors of the first heater, and the remaining volume may be occupied by air spaces through which air to be heated can flow. In an embodiment the structure is at least 60% air by volume, and in some embodiments the structure is approximately 70% air by volume. The use of lower densities may improve the efficiency of the apparatus, and the sensitivity achieved by heating the airflow. The heater may provide a constriction in the second sampling pathway, or it may be arranged around a constriction in the path of the second flow of air. In some examples the first heater may comprise an infra-red source, such as an infra-red lamp or LED, or an infra-red laser. In some examples the first heater may comprise a jet, or a plurality of jets, of hot air injected into the flow path.

The first heater may be configured to heat the flow of air to a temperature of at least 150 °C to vaporise aerosols, for example at least 200 °C, and/or wherein the heater is configured to heat the flow of air to a temperature of no more than 300 °C, for example no more than 250 °C. Thus, the heater may be configured to heat the flow of air to a temperature of from 150 °C to 300 °C, such as from 200 °C to 250 °C.

In general, the trap may suitably comprise a second heater for vaporising collected aerosols. The second heater may have any suitable configuration to permit heating of the trap to vaporise aerosols.

The trap may comprise any suitable structure or materials for collecting aerosols from a flow of air passing the trap. The trap may in general be a filter configured to allow gas and vapour to pass the trap, and to collect aerosols in the form of liquid or solid particles on the filter. For example, the trap may comprise a glass fibre material, for example glass wool. Glass fibre materials such as glass wool have been found to provide effective collection of aerosol materials whilst allowing the passage of vapours through the trap, providing selective trapping of aerosols of interest without interference of vapours that may be analysed separately while aerosols are collected on the trap.

As will be appreciated, the trap is separate from the first heater so that heating the first heater does not vaporise aerosols collected on the trap.

The collection of aerosols on the trap suitably includes any way in which the aerosol material is immobilised on the trap for subsequent vaporisation. For example, aerosol materials may be deposited on the surface of materials that make up the trap (e.g. glass io fibres), for example solid or liquid aerosol materials may be deposited on the surface of the trap material to immobilise the collected aerosols for subsequent vaporisation.

As described herein, an inlet apparatus is configured to be operable in a first mode for real time detection of aerosols in the flow of air to be tested and in a second mode for detection of aerosols collected on the trap.

Thus, in an aspect, there is provided an inlet apparatus for a detection system, the apparatus comprising: an inlet for receiving a flow of air to be tested, the inlet comprising a first heater configured to vaporise an aerosol carried by the air for sampling by an analytical apparatus; and a trap configured to collect aerosols from the flow of air and to vaporise collected aerosols for sampling by the analytical apparatus; wherein the inlet apparatus is operable: in a first mode in which the first heater is operated to vaporise aerosols carried by a first portion of the flow of air for sampling by the analytical apparatus, and in which aerosols carried by a second portion of the flow of air are collected on the trap; and in a second mode in which aerosols collected on the trap are vaporised for sampling by the analytical apparatus.

The inlet apparatus may for example comprise air movement means comprising one or more conduits configured to contain and direct the first portion of the flow of air and the second portion of the flow of air, and one or more flow providers, wherein the trap, the first heater, and the one or more flow providers are arranged in the one or more conduits for providing the first mode and the second mode.

As will be appreciated, any elements of the inlet apparatus of this aspect may be substantially as defined previously herein.

A further aspect provides a detection apparatus comprising an inlet apparatus as defined previously herein and an analytical apparatus configured to obtain samples from the inlet for detecting a substance of interest.

The analytical apparatus may comprise any suitable analyser for detecting a substance of interest in vapour form. The analytical apparatus may comprise at least one of an ion mobility spectrometer (IMS), a differential mobility spectrometer (DMS), a mass spectrometer (MS), a chromatography apparatus (for example a gas chromatography io system) and an optical spectrometer (for example an infrared spectrometer or a Raman spectrometer). In embodiments, the analytical apparatus may comprise an ion mobility spectrometer, a mass spectrometer, or a combined IMS-MS. An IMS may comprise a positive IMS and/or a negative mode IMS. In embodiments the analytical apparatus comprises both a positive mode IMS and a negative mode IMS configured to analyse samples from a single sampling volume. In some embodiments a single IMS may be switchable between positive and negative modes and may be configured to rapidly switch between positive and negative modes in order to analyse a single sample in both the positive and negative modes. The analytical apparatus preferably comprises an ion mobility spectrometer (IMS).

The detection apparatus may be portable, for example a handheld detector, and may comprise a portable power source that can be carried by the detector. A portable power source may comprise a battery, a fuel cell, a capacitor, or any other portable source of electrical power suitable for providing electrical power to the detector.

The detection apparatus may suitably be configured to draw the flow of air to be tested into the inlet from an ambient environment in which the detector is situated. For example, the detection apparatus may be configured to detect substances of interest in the air of the ambient environment in which the detector is operated (rather than drawing a flow to be sampled from another apparatus such as a chromatography apparatus or a pre-collected sample). For example, the detection apparatus may comprise a housing configured to contain the inlet apparatus and the analytical apparatus, wherein the detection apparatus is configured to draw the flow of air to be tested from the air of the ambient environment outside of the housing.

The detection apparatus may comprise a controller configured to control operation of the detection apparatus. For example, the controller may be configured to operate the detection apparatus in the first mode or the second mode as described herein. The controller may be configured to operate the detection apparatus alternately and in the first mode and the second mode a plurality of times, for example wherein the detection apparatus is operated in the first mode a majority of the time to detect in real-time the presence of substances of interest, and to intermittently operate in the second mode after a specified time period to analyse aerosol materials deposited on the trap.

io In general, whether operated in the first mode or in the second mode, the analytical apparatus may be operated to sample vapours whether or not aerosols are being vaporised by the first heater or the trap. For example, the detection apparatus may be operated in a third mode in which neither of the first heater or the trap are heated and vapours present in the flow of air to be tested are sampled for analysis. The apparatus may be operated in the third mode when the first heater is not heated and the trap is not heated. For example, the apparatus may be configured to operate in the third mode whenever the first heater and the trap are not heated. The apparatus may be operated in the third mode in any time period in which the apparatus is not operated in the first or second mode. For example, where the first heater is operated intermittently as described elsewhere herein, the apparatus may be operated in the third mode in the interval between the intermittent heating of the first heater. The apparatus may, for example, be configured to sample vapours whilst aerosols are collected on the trap. Thus, where the first heater is operated intermittently, the first mode may further comprise sampling vapours present in the flow of air to be tested for analysis.

The controller may be configured to receive an indication from the analytical apparatus that a substance of interest is detected, or is not detected, and to provide an indication to a user, such as to provide an alert to a user that a substance of interest is detected.

The controller may suitably be configured to synchronise operation of analytical apparatus with operation of flow providers, the first heater and/or the second heater to obtain samples of vaporised aerosol provided from the first heater or the trap to the analytical apparatus, for example to operate in the first mode or the second mode.

A further aspect provides a method of operating a detection apparatus for analysing vapours and aerosols, the method comprising: in a first time period, operating the detection apparatus in a first mode to: provide a flow of air to be tested into an inlet of the apparatus; heat a first portion of the flow of air to vaporise aerosols carried by the first portion of the flow of air for sampling by an analytical apparatus, whilst also collecting aerosols carried by a second portion of the flow of air on a trap; and in a second time period, operating the detection apparatus in a second mode to: vaporise collected aerosols from the trap for sampling by the analytical apparatus.

As has been described in relation to the inlet apparatus, one exemplary way to implement the present disclosure is to divide the flow of air to be tested into a first and second portion so that one portion can be analysed whilst aerosols are collected on a trap at the same time. Thus, in a preferred embodiment, in the first mode the flow of air to be tested is divided into the first portion and the second portion by directing the first portion along a first flow path past a first heater then past one or more sampling ports through which the analytical apparatus obtains samples, and directing the second portion along a second flow path comprising the trap, the second flow path extending from the first flow path upstream of the one or more sampling ports.

In the second mode collected aerosols may be vaporised from the trap and provided along the first flow path to the one or more sampling ports for sampling by the analytical apparatus, for example wherein a reverse flow is provided from the second flow path past the trap into the first flow path, or wherein the trap separates the first flow path from the second flow path and aerosol material vaporised from the trap enters the first flow path, for example by diffusion, and is carried to the one or more sampling ports by an air flow along the first flow path.

In the first mode the first portion may be provided past the first heater then past the one or more sampling ports by a first flow provider arranged in the first flow path and the 30 second portion may be provided to the trap by a second flow provider arranged in the second flow path.

In the first mode the analytical apparatus may be operated to sample and analyse aerosols vaporised by the first heater, whilst aerosols are collected on the trap, and in the second mode the analytical apparatus may be operated to sample and analyse collected aerosols vaporised from the trap.

As has been described in relation to the inlet apparatus, another exemplary way to implement the present disclosure is to provide a portion of the flow of air past the first heater to a trap downstream of one or more sampling ports, so as to allow aerosol material to be collected on the trap whilst also permitting aerosols to be vaporised for analysis. Thus, in another preferred embodiment, in the first mode the flow of air to be tested is provided along a flow path past a first heater for vaporising aerosols in the flow of air, then io past one or more sampling ports through which the analytical apparatus obtains samples for analysis, then to the trap. For example, the flow path may be provided by a conduit having walls configured to contain and direct the flow of air along the flow path.

In the first mode aerosols carried by the first portion of the flow of air may be vaporised by the first heater for sampling through the one or more sampling ports, wherein the first heater is operated intermittently during the first time period and the second portion of the flow of air passes the first heater when the heater is off to provide aerosols to the trap.

In the second mode a reverse flow may be provided along the flow path past the trap, then past the one or more sampling inlets for sampling by the analytical apparatus.

In the first mode operation of the analytical apparatus may be synchronised with operation of the first heater to sample aerosol material vaporised by the first heater through the one or more sampling ports, and in the second mode operation of the analytical apparatus may be synchronised with vaporisation of collected aerosols on the trap to sample aerosol material vaporised from the trap through the one or more sampling ports.

The method may comprise operating alternately a plurality of times in the first mode and then in the second mode. In this way, real-time detection of aerosols may be maintained, whilst also collecting low concentration aerosols for analysis intermittently.

In the first mode the flow of air to be tested may be heated intermittently for vaporising aerosols, and the analytical apparatus is operated to obtain samples from the flow of air when not heating the flow of air to sample vapours present in the flow of air. Thus, the method may comprise operating the detection apparatus during a time period in which neither the flow of air to be tested or the trap are heated and vapours present in the unheated flow of air to be tested are sampled for analysis.

It will be appreciated that the detector referred to in relation to the methods may comprise a detector or inlet apparatus as described elsewhere herein, and the method may comprise controlling the detector or inlet apparatus as described previously herein. For example, the method may comprise operation of a detector or inlet apparatus with a controller as described herein. For example, the methods may be implemented by the controller according to instructions stored in a memory of the controller.

The controller described herein may suitably be provided by any appropriate control logic, such as analogue control circuitry and/or digital processors, examples include field programmable gate arrays, FPGA, application specific integrated circuits, ASIC, a digital signal processor, DSP, or by software loaded into a programmable processor. Aspects of the disclosure comprise computer program products, and may be recorded on non-transitory computer readable media, and these may be operable to program a processor to perform any one or more of the methods described herein.

A further aspect provides a computer program product configured to program a controller of a detection apparatus to perform the methods disclosed herein, or fixed logic circuitry configured to control a detection apparatus to perform the methods disclosed herein.

Brief Description of Figures

Examples of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1A shows a schematic illustration of a detection apparatus comprising an ion mobility spectrometer coupled to an inlet apparatus operating in a first mode; Figure 1B shows a schematic illustration of a detection apparatus comprising an ion mobility spectrometer coupled to an inlet apparatus operating in a second mode; Figure 2A shows a schematic illustration of a detection apparatus comprising an ion mobility spectrometer coupled to an alternative inlet apparatus operating in a first mode; Figure 2B shows a schematic illustration of a detection apparatus comprising an ion mobility spectrometer coupled to an alternative inlet apparatus operating in a second mode; Figure 3 shows a schematic illustration of a detection apparatus comprising two sampling ports; and Figure 4 illustrates a method of operating a detection apparatus.

In the drawings like reference numerals are used to indicate like elements.

Specific Description

The present disclosure relates to detector inlets comprising a heater for vaporising aerosols in a flow of air to be tested as they pass through the inlet to an analytical apparatus for analysis and a trap for collecting aerosols from the flow of air.

Figure 1A shows a detection apparatus 100 comprising an inlet 102 for receiving a flow of air to be tested 104. The inlet comprises a first flow path 108 defined by a first conduit 109, and a second flow path 110 defined by a second conduit 111. The first and second conduits 109/111 are enclosed flow paths bounded by walls that contain and direct fluid flow along the first and second flow paths 108/110. The inlet 102 comprises a common inlet portion 112 comprising a conduit that receives the flow of air to be tested 104 and provides it to the first and second flow paths 108/110.

The inlet 102 divides into the first and second flow paths 108/110 at a junction 106. As shown in Figure 1A, in a first mode a first flow provider 114 and a second flow provider 116 (each flow provider for example comprising a fan or any other suitable air movement device) are simultaneously operated to draw the flow of air 104 along both the first flow path 108 and the second flow path 110. As shown in Figure 1A, the flow past the first and second flow providers 114/116 is provided to an exhaust 130 from the detection apparatus.

The second flow path 110 comprises a trap 118 at the entrance to the second flow path 110/second conduit 111. The trap 118 separates the second flow path 110 from the first flow path 108 by extending across the diameter of the second conduit 111 at the junction 106 between the first and second flow paths 108/110. The trap 118 may for example comprise a glass fibre structure that permits passage of vapours and gas, whilst capturing solid and liquid aerosol particles. The trap 118 may for example comprise glass wool.

A first heater 120 is arranged in the first flow path 108, downstream of the entrance of the second flow path and the trap 118. The first heater 120 is arranged to extend across the first conduit 109 so that when the first heater 120 is operated, aerosols present in the flow of air 104 passing along the first flow path 108 are vaporised and carried downstream of the first heater 120 to a sampling port 122 configured to obtain samples for analysis from a sampling volume 124 in the first flow path 108 adjacent the sampling port 122. The first io heater 120 may for example comprise an array of elongate conductors that extend across the diameter of the first conduit 109.

In the first mode as shown in Figure 1A, a first portion of the flow of air to be tested is drawn by the first flow provider 114 along the first flow path 108 past the first heater 120.

The first heater 120 is operated to heat and vaporise aerosols present in the first portion of the flow of air, and the vaporised aerosols pass along the first flow path 108 to the sampling volume 124 for sampling by the spectrometer 302 via the sampling port 122.

Also in the first mode, a second portion of the flow of air to be tested is drawn by the second flow provider 116 into the second flow path 110. The second portion of the flow of air passes through the trap 118 and aerosols present in the second portion of the flow of air are collected on the trap 118.

The first heater 120 is arranged in the first flow path 108, downstream of the entrance of the second flow path 110 and the trap 118. In this way, aerosols may be collected on the trap 118 at the same time as the first heater 120 is operated to vaporise aerosols for sampling via the sampling port 122. In alternative examples, the first heater may be arranged upstream of the trap 118 in the inlet 102, in which case the first heater 120 may be operated intermittently so as to provide vaporised aerosols along the first flow path 108 for sampling, and in the intermittent time periods when the first heater is not active, aerosols flow past the heater 120 and can be collected on the trap 118. It will be appreciated that when the first heater 120 is upstream of the trap 118, when the first heater 120 is active, aerosols are vaporised by the first heater 120 and can pass the trap 118 without collection. While the first heater 120 is not heated, the apparatus can also be operated to sample vapours from the first flow path 108 via the sampling port 122. In this way, it may be possible to save power in connection with powering the first heater 120 (to vaporise and detect aerosols) whilst maintaining continuous detection of vapours in the flow of air to be tested.

Thus, in the first mode as shown in Figure 1A, aerosols are collected on the trap 118 and also vaporised by the first heater 120 for sampling through the sampling port 122. In this way, low concentration aerosols can be concentrated on the trap 118, without the need to halt real-time analysis of aerosols in the flow of air to be tested 104.

io Figure 1B shows the detection apparatus of Figure 1A operating in a second mode. In the second mode, the trap 118 is heated by a second heater, the second heater of the trap 118 arranged to heat the trap material so as to vaporise aerosol materials collected on the trap 118. The second flow provider 116 is operated in reverse to provide a reverse flow along the second flow path 110 as compared to operation in the first mode, whilst the first flow provider 114 maintains a flow along the first flow path 108 from the first heater 120 past the sampling port 122. Vaporised aerosols from the trap 118 are thus carried to the first flow path 108 for sampling via the sampling port 122. Whilst Figure 1B shows the second flow provider 116 operating in reverse, it will be appreciated that in the second mode the second flow provider may alternatively be inactive, in which case aerosol material vaporised from the trap 118 can pass by diffusion into the junction 106 to be carried along the first flow path 108 for sampling by via the sampling port 122.

In Figures 1A/1B and Figures 2A/2B, the analytical apparatus is shown as a spectrometer 302, which comprises an ion mobility spectrometer coupled to the sampling volume 124 by the sampling port 122. The spectrometer 302 comprises a reaction region 308 in which a sample can be ionised. The sampling port 122 can be operated to obtain a sample from the sampling volume 124 into the spectrometer 302. A gate electrode 310 may separate the reaction region 308 from a drift chamber 312. The drift chamber 312 comprises a collector 314 toward the opposite end of the drift chamber 312 from the gate electrode 310. In other embodiments, an ion mobility spectrometer may be operated with an ion trap holding and releasing sample ions in place of the gate electrode 310. The drift chamber 312 also comprises a drift gas inlet 316, and a drift gas outlet 318 arranged to provide a flow of drift gas along the drift chamber 312 against the direction of movement of sample ions towards the collector 314, for example a drift gas flow is provided from the collector 314 towards the gate 310. The sampling port 122 can be operated to sample air from the sampling volume 124 into the reaction region 308 of the spectrometer 302. The reaction region 308 comprises an ioniser 320 for ionising a sample. In the example shown in Figures 1A/1B and Figures 2A/2B the ioniser 320 comprises a corona discharge ioniser comprising electrodes. The drift chamber 312 also comprises drift electrodes 322, 324, for applying an electric field along the drift chamber 312 to accelerate ions towards the collector 314 against the flow of the drift gas. The detector may comprise a sampler (not shown) configured to draw a selected volume of fluid, smaller than the sampling volume 124, through the sampling port 122 to provide a sample to the analytical apparatus. The sampler may comprise an electromechanical actuator, for example a solenoid driven io actuator, and/or a mechanical pump arranged to transfer vapour from the sampling volume 124 through the sampling port 122 and into the analytical apparatus/spectrometer 302.

Figure 2A shows a detection apparatus 200 comprising an inlet 202 for receiving a flow of air to be tested 204. The inlet comprises a single conduit 212 configured to contain and direct the flow of air to be tested 204 through the inlet 202 to an exhaust 230. As shown in Figure 2A, the inlet 202/conduit 212 has a first end 240 configured to receive the flow of air to be tested 204 and a second end 250 from which an exhaust flow is shown as being provided to an exhaust 230.

A first heater 220 is arranged in the inlet 202 at the first end 240. The first heater 220 is arranged to extend across the conduit 212 so that when the first heater 220 is operated, aerosols present in the flow of air 204 passing along through the inlet are vaporised and carried downstream of the first heater 220 to a sampling port 222 configured to obtain samples for analysis from a sampling volume 224 in the inlet 202 adjacent the sampling port 222. The first heater 220 may for example comprise an array of elongate conductors that extend across the diameter of the inlet 202.

The inlet 202 also comprises a trap 218 at the second end 250, so that when the flow provider 214 is operated in the first mode shown in Figure 2A, the flow of air to be tested 204 passes the first heater 220, then passes the sampling port 222, to arrive at the trap 218. The trap 218 extends across the diameter of the inlet 202 and is configured to collect aerosols in a flow of air that passes the trap 218 to the exhaust 230. The trap 218 may for example comprise a glass fibre structure that permits passage of vapours and gas, whilst capturing solid and liquid aerosol particles. The trap 218 may for example comprise glass w001.

Figure 2A shows schematically operation of the detection apparatus 200 in a first mode in which the flow provider 214 is operated to provide the flow of air to be tested 204 past the first heater 220, past the sampling port 222, then to the trap 218. The first heater 220 is operated to heat and vaporise aerosols present in the flow of air to be tested 204. The vaporised aerosols then pass along the inlet 202 into the sampling volume 224 from which samples are obtained by the analytical apparatus (spectrometer 302) via the sampling inlet 222.

io In the first mode, the first heater 220 is operated in a pulsed manner to provide heating intermittently. Thus, when the first heater 220 is active, vaporised aerosols in the flow of air 204 are sampled for analysis as described above. In addition, in the time periods between heating pulses of the first heater 220, when the first heater does not heat the flow of air 204 entering the inlet, aerosols in the flow of air 204 pass the first heater 220 unvaporised and are provided along the inlet 202 to the trap 218, on which the aerosols are collected. Thus, by operating the first heater 220 in a pulsed manner in the configuration shown in Figure 2A, real-time sampling of vaporised aerosols in the flow of air 204 can be conducted, whilst also permitting aerosols that may be present in the flow of air 204 at low concentrations (or low number density) to accumulate on the trap.

As shown in Figure 2B, in the second mode, a reverse flow is provided by the flow provider 214 from the second end 250 to the first end 240 of the inlet 202. At the same time, the trap 218 is heated by a second heater, the second heater of the trap 218 arranged to heat the trap material so as to vaporise aerosol materials collected on the trap 218. Vaporised aerosol materials collected on the trap are thereby carried by the reverse flow through the inlet 202 to the sampling inlet 222 for sampling by the spectrometer 302. As shown in Figure 2A, aerosols arriving at the trap 218 for collection arrive at the side of the trap 218 that is closer to the sampling volume 224 and sampling port 222. Thus, when the collected aerosol materials are vaporised by the second heater, it is not necessary for the vaporised aerosols to pass through the trap structure in order to reach the sampling port 222.

Figure 3 shows a schematic view of an inlet apparatus 201 that comprises more than one sampling port in the inlet. The inlet apparatus 201 corresponds to that of Figures 2A and 2B, with the exception that in place of a single ion mobility spectrometer, two ion mobility 35 spectrometers 302a and 302b are provided. For example, the spectrometers 302a and 302b may be configured to operate in different modes, in particular to provide one positive mode ion mobility spectrometer and one negative mode spectrometer. The spectrometer 302a is configured to obtain samples via sampling port 222a, while spectrometer 302b is configured to obtain samples via sampling port 222b. It will be appreciated that while Figure 3 shows the structure of Figure 2A/B, it will be appreciated that the dual IMS configuration shown in Figure 3 could also be used in the configuration shown in Figure 1A/B. Figure 3 is intended to show generally how an inlet/detection apparatus comprising more than one sampling port can be arranged. In addition, while Figure 3 shows spectrometers 302a and 302b as being spaced along the length of the inlet 202, the spectrometers/sampling ports could in other embodiments be spaced around the diameter of the inlet 202 such that the sampling ports 302a/302b are the same distance from the first heater 220 and the trap 218 (for example at the upper and lower side of the inlet as shown in Figure 3).

Figure 4 illustrates a method 400 of operating a detection apparatus for analysing vapours in real-time whilst collecting low concentration aerosols on a trap. As shown in Figure 4, the method comprises 402 providing a flow of air to be tested to an inlet of the detection apparatus. In a first time period, while operating in a first mode, steps 404, 406 and 408 are conducted. At step 404, a first portion of the flow of air to be tested is heated to vaporise aerosols in the flow of air and at step 406, vaporised aerosols from the first portion are sampled by an analytical apparatus for analysis. Also in the first time period, aerosols present in a second portion of the flow of air are collected on a trap.

Finally, in a second time period, operating in a second mode, at step 410, aerosol materials that are captured on the trap are vaporised, for example by heating the trap, and the vaporised aerosol material from the trap is sampled by an analytical apparatus for analysis.

As will be appreciated, while Figure 4 only shows operation in the first and second modes, The analytical apparatus may also be operated to sample vapours whether or not aerosols are being vaporised for analysis (for example by the first heater or the trap). For example, where the heating of the flow of air to vaporise aerosols is performed intermittently as described elsewhere herein, the method may comprise sampling vapours in the flow of air to be tested for analysis in the intervals between the intermittent heating of the flow of air to be tested. For example, vapours may be sampled for analysis at the same time as collection of aerosols on the trap at step 408, for example while the flow of air to be tested is not heated prior to sampling.

Although embodiments of the disclosure have been described as having particular application in ion mobility spectrometers, the apparatus and methods described may be applied in other analysis systems where there is a need to test for vapours such as vapours associated with aerosols having a low vapour pressure.

As will be appreciated a vapour may comprise a substance in its gaseous phase at a temperature lower than its critical point. By contrast with a vapour or gas, an aerosol comprises fine particles of solid or liquid suspended in a gas. As used herein, the term "vaporise" is used to mean converting at least some of a substance from a solid or liquid to a vapour or a gas.

In general, apparatus features described herein may be provided as method features, and vice versa.

It should also be appreciated that particular combinations of the various features described and defined in any aspects of the invention can be implemented and/or supplied and/or used independently. Other examples and variations will be apparent to the skilled addressee in the context of the present disclosure.

Claims

CLAIMS: 1. An inlet apparatus for a detection system, the apparatus comprising: an inlet for receiving a flow of air to be tested, the inlet comprising a first heater configured to vaporise an aerosol carried by the air for sampling by an analytical apparatus; a trap configured to collect aerosols from the flow of air and to vaporise collected aerosols for sampling by the analytical apparatus; wherein the inlet apparatus is configured to provide the flow of air to be tested: (i) to the first heater to enable vaporisation of aerosols in the flow of air for sampling by the analytical apparatus, and (ii) to the trap to collect aerosols on the trap while the flow of air is being provided to the first heater.
2. The inlet apparatus of claim 1, wherein the inlet comprises: a first flow path comprising the first heater and one or more sampling ports downstream from the first heater through which the analytical apparatus can obtain samples from the inlet; a second flow path comprising the trap; a first flow provider for moving a first portion of the flow of air along the first flow path from the first heater past the one or more sampling ports; and a second flow provider for moving a second portion of the flow of air along the second flow path past the trap.
3. The inlet apparatus of claim 2, wherein the second flow path extends from the first flow path upstream of the one or more sampling ports.
4. The inlet apparatus of claim 2 or claim 3, wherein the second flow path is separated from the first flow path by the trap.
5. The inlet apparatus of claim 3 or claim 4, wherein the trap is arranged so that when the second flow provider is off, or when the second flow provider provides a reverse flow from the trap into the first flow path, vaporised aerosols vaporised from the trap can enter the first flow path for sampling by the one or more sampling ports.
6. The inlet apparatus of any one of claims 2 to 5, wherein the first flow path is defined by a first conduit configured to direct the first portion of the flow of air past the first heater then past the one or more sampling ports, the one or more sampling ports configured to provide samples through a wall of the first conduit to the analytical apparatus.
7. The inlet apparatus of claim 6, wherein the second flow path is defined by a second conduit that splits from the first conduit at a junction upstream of the one or more sampling ports, and wherein the trap is disposed at the junction of the first and second conduits to collect aerosols present in the second portion of the flow of air entering the second conduit whilst permitting aerosols in the first portion of the flow of air to pass along the first conduit.
8. The apparatus of any one of claims 2 to 7, wherein the inlet apparatus is operable in a first mode in which the first heater is operated to vaporise aerosols carried by the first portion of the flow of air for sampling by the analytical apparatus, and in which aerosols carried by the second portion of the flow of air are collected on the trap; and in a second mode in which aerosols collected on the trap are vaporised for sampling by the analytical apparatus.
9. The inlet apparatus of claim 8, wherein in the first mode the first flow provider and the second flow provider are operable at the same time to provide the first portion of the flow of air along the first flow path and the second portion of the flow of air along the second flow path.
10. The inlet apparatus of claim 9, wherein the inlet apparatus is operable in the second mode so that when the second flow provider is off or is operated in reverse, collected aerosols vaporised from the trap enter the first flow path and are provided by the first flow provider to the one or more sampling ports.
11. The inlet apparatus of claim 1, wherein the inlet defines a flow path having a first end and a second end the first end configured to receive the flow of air to be tested, the inlet comprising: one or more sampling ports through which the analytical apparatus can obtain samples from the inlet, the one or more sampling ports arranged between the first heater and the second end so that aerosols flowing through the inlet from the first end to the second end can be vaporised by the first heater and provided to the one or more sampling ports; wherein the trap is arranged between the one or more sampling ports and the second end so that aerosols carried by the flow of air past the first heater and past the one or more sampling ports are collected on the trap.
12. The inlet apparatus of claim 11, wherein the inlet comprises a conduit configured to contain and direct the flow of air to be tested along the flow path.io
13. The inlet apparatus of claim 11 or claim 12, comprising a flow provider operable in a first mode to provide a first flow through the inlet from the first end to the second end, the flow provider operable in a second mode to provide a second flow through the inlet from the second end to the first end.
14. The inlet apparatus of claim 13, wherein in the first mode, the first heater is operable to provide intermittent heating so as to allow aerosols in the first portion to pass the first heater unvaporised for collection on the trap.
15. The inlet apparatus of claim 13 or claim 14, wherein in the second mode, the trap is operable to vaporise collected aerosols to be carried by the second flow for sampling by the analytical apparatus through the one or more sampling pods.
16. The inlet apparatus of any one of the preceding claims, wherein the trap comprises a second heater for vaporising collected aerosols.
17. The inlet apparatus of any one of the preceding claims, wherein the trap comprises a glass fibre material, for example glass wool.
18. The inlet apparatus of any one of the preceding claims, wherein the first heater comprises conductors arranged across the inlet so that the flow of air to be tested passes between the conductors, for example wherein the first heater comprises an array of elongate conductors or wires extending across the inlet, for example a grid or an array of parallel elongate conductors.
19. An inlet apparatus for a detection system, the apparatus comprising: an inlet for receiving a flow of air to be tested, the inlet comprising a first heater configured to vaporise an aerosol carried by the air for sampling by an analytical apparatus; and a trap configured to collect aerosols from the flow of air and to vaporise collected aerosols for sampling by the analytical apparatus; wherein the inlet apparatus is operable: in a first mode in which the first heater is operated to vaporise aerosols carried by a first portion of the flow of air for sampling by the analytical apparatus, and in which aerosols carried by a second portion of the flow of air are collected on the trap; and in a second mode in which aerosols collected on the trap are vaporised for sampling by the analytical apparatus.
20. The apparatus of claim 19, wherein the inlet apparatus is as further defined in any one of claims 2 to 18.
21. A detection apparatus comprising the inlet apparatus of any one of the preceding claims and an analytical apparatus configured to obtain samples from the inlet for detecting a substance of interest, for example wherein the analytical apparatus comprises an ion mobility spectrometer.
22. A method of operating a detection apparatus for analysing vapours and aerosols, the method comprising: in a first time period, operating the detection apparatus in a first mode to: provide a flow of air to be tested into an inlet of the apparatus; heat a first portion of the flow of air to vaporise aerosols carried by the first portion of the flow of air for sampling by an analytical apparatus, whilst also collecting aerosols carried by a second portion of the flow of air on a trap; and in a second time period, operating the detection apparatus in a second mode to: vaporise collected aerosols from the trap for sampling by the analytical apparatus.
23. The method of claim 22, wherein in the first mode the flow of air to be tested is divided into the first portion and the second portion by directing the first portion along a first flow path past a first heater then past one or more sampling ports through which the analytical apparatus obtains samples, and directing the second portion along a second flow path comprising the trap, the second flow path extending from the first flow path upstream of the one or more sampling ports.
24. The method of claim 23, wherein in the second mode collected aerosols are vaporised from the trap and provided along the first flow path to the one or more sampling ports for sampling by the analytical apparatus; for example wherein a reverse flow is provided from the second flow path past the trap into the first flow path, or wherein the trap separates the first flow path from the second flow path and aerosol material vaporised io from the trap enters the first flow path and is carried to the one or more sampling ports by an air flow along the first flow path.
25. The method of claim 24, wherein in the first mode the first portion is provided past the first heater then past the one or more sampling ports by a first flow provider arranged in the first flow path and the second portion is provided to the trap by a second flow provider arranged in the second flow path.
26. The method of any one of claims 23 to 25, wherein in the first mode the analytical apparatus is operated to sample and analyse aerosols vaporised by the first heater, whilst aerosols are collected on the trap, and in the second mode the analytical apparatus is operated to sample and analyse collected aerosols vaporised from the trap.
27. The method of claim 22, wherein in the first mode the flow of air to be tested is provided along a flow path past a first heater for vaporising aerosols in the flow of air, then past one or more sampling ports through which the analytical apparatus obtains samples for analysis, then to the trap, for example wherein the flow path is provided by a conduit having walls configured to contain and direct the flow of air along the flow path.
28. The method of claim 27, wherein in the first mode aerosols carried by the first portion of the flow of air are vaporised by the first heater for sampling through the one or more sampling ports, wherein the first heater is operated intermittently during the first time period and the second portion of the flow of air passes the first heater when the heater is off to provide aerosols to the trap.
29. The method of claim 27 or claim 28, wherein in the second mode a reverse flow is provided along the flow path past the trap, then past the one or more sampling inlets for sampling by the analytical apparatus.
30. The method of any one of claims 27 to 29, wherein in the first mode operation of the analytical apparatus is synchronised with operation of the first heater to sample aerosol material vaporised by the first heater through the one or more sampling ports, and in the second mode operation of the analytical apparatus is synchronised with vaporisation of collected aerosols on the trap to sample aerosol material vaporised from the trap io through the one or more sampling ports.
31. The method of any one of claims 22 to 30, wherein the method comprises operating alternately a plurality of times in the first mode and then in the second mode.
32. The method of any one of claims 22 to 31, wherein in the first mode the flow of air to be tested is heated intermittently for vaporising aerosols, and the analytical apparatus is operated to obtain samples from the flow of air when not heating the flow of air to sample vapours present in the flow of air.
33. The detection apparatus of claim 21, comprising a controller configured to control the detection apparatus to perform the method of any one of claims 22 to 32.
34. A computer program product configured to program a controller of a detection apparatus to perform the method of any one of claims 22 to 32, or fixed logic circuitry configured to control a detection apparatus to perform the method of any one of claims 22 to 32.