WO2022234261A1

WO2022234261A1 - In-room air quality sensing apparatus, air quality control system, and air quality sensor device

Info

Publication number: WO2022234261A1
Application number: PCT/GB2022/051120
Authority: WO
Inventors: Matthew Edward Thomas White; Keith Noel Jenkins; Gary Bryan Wordsworth
Original assignee: Elta Group Limited
Priority date: 2021-05-05
Filing date: 2022-05-04
Publication date: 2022-11-10

Abstract

An in-room air quality sensing apparatus (10) is provided comprising a housing (12) having an air inlet (18) and an air outlet (20) and an electrically-energisable fan (32) which is configured to create an airflow path from the air inlet (18) to the air outlet (20). A plurality of different air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) is mounted on the airflow path, and a processor (53) is provided in communication with the plurality of air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) The processor (53) is configured to calculate gas concentrations for a plurality of different gases on the airflow path based on cross-sensitivities of the plurality of different air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i).

Description

In-Room Air Quality Sensing Apparatus, Air Quality Control System, and Air Quality Sensor Device

The present invention relates to an in-room air quality sensing apparatus, which is particularly but not necessarily for providing a holistic or statistical control methodology to an air quality control system. The invention further relates to a method of calibrating such an apparatus. An air quality control system is provided which utilises an in-room air quality sensing apparatus in conjunction with one or more airflow control devices. The invention further relates to an air quality sensor device which is adapted for determining the composition of at least one component of air in a room, and preferably which is wirelessly communicable with other ventilation and filtration systems for the room.

Airflow control within a building is controlled by one or more airflow control devices, typically ventilation fans, positioned around the building. Some ventilation systems may be activated in response to sensing of unexpected changes to the gas composition of the air in order to flush the building of contaminants. This has several problems: firstly, air quality sensing is difficult, and therefore existing sensors will be calibrated to a specific gas to be sensed, such as carbon monoxide. If more than one gas is desirable to be monitored, then the installer must create multiple gas sensing systems. This is extremely unwieldy.

Secondly, the need to provide a wide variety of sensor systems means that there is no consistency of measurement. The sensing of the gas occurs at the location of the sensor, and therefore it is preferred that the expected type of gas sensor be provided in locations of likely contamination, for example, nitrogen dioxide near windows by high vehicular traffic locations, carbon monoxide near fossil fuel burning sources, and so on. The gas being sampled is not the same in each case, so there is no capacity for building a true picture of the gas composition within a building.

Thirdly, the systems are extremely non-portable, and must be installed bespoke to a building. This is time-consuming and prohibitively expensive.

It is an object of the present invention to provide an air quality control system which is highly modularised, and thus suitable for use in a wide variety of contexts, whilst also providing much more detailed information about the gas composition within a building. Furthermore, for ventilation and filtration systems in buildings, it is useful to know what the status of the air being treated is. Typically, the system owner will be interested in the gas composition, particularly in relation to carbon dioxide and pollutants, as well as an indication of the level of particulate matter in the air.

An air quality sensor can be used to provide this information. However, there are various challenges associated with air quality monitoring.

Firstly, where lots of different air quality characteristics are to be measured, an equivalent number of sensors is required. This can result in a bulky device, which is not aesthetically pleasing, and/or is cumbersome to move.

Where bulky components are present, this can necessitate a large internal volume of the device, which can lead to recirculation of the air flowing through the device. This means that the sensors may be monitoring recirculated air, rather than fresh air from outside of the device. This can skew the measurements being made.

Furthermore, the largely sealed nature of such air quality sensor devices is required to prevent damage or contamination of the sensor components. However, this can lead to clogging of the air inlet and outlet of the device with dust, since the user cannot readily clean the device.

It is a further object of the present invention to provide an air quality sensor device which overcomes or obviates the above-referenced problems.

According to a first aspect of the invention, there is provided an in-room air quality sensing apparatus comprising: a housing having an air inlet and an air outlet; an electrically-energisable fan which is configured to create an airflow path from the air inlet to the air outlet; a first air quality sensor mounted on the airflow path having a primary gas sensitivity for a first gas and a secondary gas sensitivity for a second gas, the first air quality sensor producing a first sensor output; a second air quality sensor mounted on the airflow path having a primary gas sensitivity for a third gas and a secondary gas sensitivity for the said second gas, the second air quality sensor producing a second sensor output; and a processor in communication with the first and second air quality sensors to receive the first and second sensor output signal therefrom, the processor being configured to calculate gas concentrations for each of the first, second, and third gases. The use of multiple different sensors within a single package, coupled by an onboard processor, makes use of a phenomenon known as cross-sensitivity, in which the air quality sensor provides an output which is based on a composite measurement from different gas components. Most gas sensors deem this to be problematic for accuracy of measurement; however, in the present invention, the cross-sensitivities provide sufficient date to allow for the determination of multiple different gas concentrations based on a few individual sensor readings. By doing so, the air within the in-room air quality sensing device can be analysed quickly and continuously, so that changes in gas composition can be promptly detected. This in turn allows for much improved control of airflow within a building to be realised.

Optionally, the processor may be configured to calculate the gas concentrations based on any or all of: a plurality of linear equations; a plurality of non-linear equations; and machine learning.

The cross-sensitivity information may be determinable by the solution of linear equations, which can be calculated very quickly to provide live gas concentration information for a large number of different gases. Other suitable solutions may be mathematically feasible, including machine learning techniques.

Preferably, the first and second air quality sensors may be adjacent to one another within the housing on the airflow path.

The co-location of the air quality sensors together ensures that the same air on the airflow path is being sensed, thus resulting in an accurate live overview of the gas composition at the in-room air sensing apparatus.

In one preferable embodiment, the first and second air quality sensors may be mounted to the same circuit substrate within the housing.

Mounting of the sensors onto the same circuit substrate further improves the accuracy of the gas measurement, whilst also allowing for a more compact structure to be created. A more compact structure limits the propensity for gas recirculation within the apparatus, which could lead to inaccurate readings.

The in-room air quality sensing apparatus may further comprise a wireless communication element in communication with the processor, the wireless communication element having a communication frequency of less than 1GHz. Sub-GHz communications are capable of transmitting through otherwise communications-disrupting structures within a building, such as steel beams, thick concrete, and stone walls. This is a significant improvement over Wi-Fi (RTM) enabled technology.

Optionally, the air inlet and air outlet may be at opposite ends of the housing.

Positioning the air inlet and outlet opposite to one another further limits the propensity for air recirculation within the housing, ensuring that it is always a fresh air sample which is being sensed in the apparatus.

The processor may be an onboard processor, or an external processor.

According to a second aspect of the invention, there is provided a method of calibration of an in-room air quality sensing device in accordance with the first aspect of the invention, the method comprising the steps of: a] passing a gas mixture along the airflow path having a known concentration of the first gas; a known concentration of the second gas; and a known concentration of the third gas; and b] calibrating the first and second sensor output signals based on the calculated gas concentrations of the first, second and third gases by the processor.

It is much preferred that calibration be performed on a device-specific basis, rather than relying on the manufacturer’s predetermined cross-sensitivity parameters, which may have an inbuilt tolerance to them. The device may be capable of improved accuracy if device-specific calibration is performed.

According to a third aspect of the invention, there is provided an air quality sensing system comprising: a plurality of different air quality sensors; and a processor in communication with the plurality of air quality sensors, the processor being configured to calculate gas concentrations for a plurality of different gases based on cross-sensitivities of the plurality of different air quality sensors.

Cross-sensitivity can be utilised within the present invention to achieve gas sensing which is greater than the sum of its parts. Concentrations of a greater number of gases can be accurately determined than the number of sensors present, which drastically reduces installation cost and disruption. Notably, whilst the device previously described allows for a fan to control the airflow through the housing, processing based on cross sensitivities can be achieved in many different apparatus configurations, including but not limited to external sensor arrangements. Indeed, arrangements in which sensing is performed across several different sensing devices within a building, location or site may be conceivable within the scope of the present invention.

Preferably, the plurality of different air quality sensors may be provided as part of an in room air quality sensing apparatus having an airflow path therethrough. There may be at least three, and more preferably at least six, different air quality sensors mounted on the airflow path.

The greater the number of air quality sensors, the better. At least three provides sufficient data for the main gases which should be monitored within a building, whereas six or more sensors will typically provide complete and accurate coverage of the full spectrum of gases which can be detected using commercially available gas sensors.

The apparatus may further comprise a housing having an air inlet and an air outlet, and an electrically energisable fan which is configured to create the airflow path from the air inlet to the air outlet. In one embodiment, the plurality of different air quality sensors may be mounted on a single circuit substrate within the housing.

A plurality of said processors is provided.

It will be appreciated that a sole processor is not a strict requirement of the system, and cloud-based or other non-centralised processing options are feasible. According to a fourth aspect of the invention, there is provided an air quality control system comprising: an in-room air quality sensing apparatus including: a housing having an air inlet and an air outlet; an electrically-energisable fan which is configured to create an airflow path from the air inlet to the air outlet; at least one air quality sensor mounted on the airflow path; a first processor in communication with the at least one air quality sensor to receive a sensor output signal therefrom, the first processor being configured to generate a command signal based on the sensor output signal; a first wireless communication element in communication with the processor; and a plurality of airflow control devices, each device including: a housing having an air inlet and an air outlet; an electrically- energisable fan which is configured to create an airflow path from the air inlet to the air outlet; a second wireless communication element communicable with the wireless communication element of the in-room air quality sensing apparatus to receive the command signal therefrom; a second processor in communication with the wireless communication element, the second processor being configured to control the electrically-energisable fan of the airflow control device in response to the command signal.

The in-room air quality sensing apparatus provides a large amount of information about the air quality within a building. It can thus be used as the brain of the air quality control system by providing control signals to many other air control devices within the building. This eliminates the need to provide any localised sensing capability for each of the individual air quality control devices, allowing them to act as slave units to the master in room air quality sensing apparatus. Processing requirements are thus drastically reduced across the system as a whole.

Preferably, the in-room air quality sensing apparatus may include a plurality of said air quality sensors.

Optionally, the processor of the in-room air quality sensing apparatus may be configured to calculate gas concentrations for a plurality of different gases on the airflow path based on cross-sensitivities of the plurality of different air quality sensors.

In one preferred embodiment, the first and second wireless communication elements may have a communication frequency of less than 1GHz.

Preferably, the plurality of airflow control devices may comprise at least one of: an in room air filter; an extractor fan; and a positive input ventilation unit.

There are lots of different airflow control devices which could be controlled by a centralised in-room air quality sensing apparatus.

Optionally, each of the plurality of airflow control devices may be provided in a different location.

The wireless communication between the in-room air quality sensing apparatus and the airflow control devices allows for a widespread control system to be provided across a building or site, without the need to provide localised sensing capability.

The first processor may be configured to generate an airflow-control-device-specific command signal based on the sensor output signal, depending on a location of each of the plurality of airflow control devices. Changes in gas concentration detected at the in-room air quality sensing apparatus may be indicative of problems in different locations. Methane, for instance, may be indicative of a gas leak. The in-room air quality sensing apparatus may be provided with control software which is able to provide specific command signals to different airflow control devices, depending on which gases are detected.

According to a fifth aspect of the invention, there is provided an air quality control system comprising: an in-room air quality sensing apparatus including: at least one air quality sensor mounted on the airflow path; a processor in communication with the at least one air quality sensor to receive a sensor output signal therefrom, the processor being configured to generate a command signal based on the sensor output signal; a wireless communication element in communication with the processor, the wireless communication element having a communication frequency of less than 1GHz; and at least one airflow control device including: a housing having an air inlet and an air outlet; an electrically-energisable fan which is configured to create an airflow path from the air inlet to the air outlet; a wireless communication element communicable with the wireless communication element of the in-room air quality sensing apparatus to receive the command signal therefrom, the wireless communication element having a communication frequency of less than 1GHz; a processor in communication with the wireless communication element, the processor being configured to control the electrically-energisable fan of the airflow control device in response to the command signal.

According to a sixth aspect of the invention, there is provided a method of installing a providing air quality control in a building or site having communications-disrupting structures, the method comprising the steps of: a] providing an air quality control system in accordance with the sixth aspect of the invention; and b] configuring the in-room air quality sensing apparatus and at least one airflow control device to communicate to one another at a communication frequency of less than 1GHz.

Sub-GHz communications protocols advantageously can communicate through otherwise communications-disrupting structures, such as steel beams, concrete, or stone walls.

According to a seventh aspect of the invention, there is provided an air quality sensor device comprising: a housing having a first end portion having an air inlet, a first housing chamber, a second housing chamber, and a second end portion which is opposite the first end portion and having an air outlet; an electrically-energisable fan located in the first housing chamber which is configured to create an air flow path from the air inlet, through the first housing chamber, into the second housing chamber, and to the air outlet; an airflow director which directs air from the first housing chamber into the second housing chamber so as to enter the second housing chamber at or adjacent to the first end portion; and at least one air quality sensor element mounted in the second housing chamber on the air flow path; the air flow path extending through the second housing chamber from the first end portion to the second end portion.

An air flow path through the device can be realised which minimises recirculation of air passing through. This ensures that sensing capabilities are performed on fresh air entering the device, limiting the propensity for eddy currents forming at or adjacent to the sensor elements.

Optionally, the at least one air quality sensor element may be mounted at or adjacent to a longitudinal side of the housing.

Firstly, positioning the air quality sensors along one of the longitudinal sides ensures that air flow is not redirected back along the intended direction of travel, since the circuit substrate to which the sensor elements are mounted is itself aligned to a flat plane. Furthermore, the longitudinal side positioning also assists with the miniaturisation of the device, since space-saving provisions can be considered, such as the use of a foldable circuit substrate.

Preferably, a plurality of said air quality sensor elements may be provided.

An air quality sensor can provide feedback to a much greater range of devices where a plurality of different sensors is provided.

The first end portion may include a baffle chamber positioned on the air flow path between the first and second housing chambers, the baffle chamber forming the airflow director.

A baffle chamber has the advantage of redirecting air flow through the air quality sensor device prior to passage through the second housing chamber so greatly improve the linearity of flow across the sensor elements. This vastly reduces the likelihood of recirculation within the air quality sensor device. Preferably, space-saving advantages can also be created by forming the baffle chamber at least in part using an end cap of the device, effectively creating a turn in the air flow path directly at one end of the device.

In one preferable embodiment, the device may further comprise a filter element receivable in the baffle chamber upstream of the second housing chamber.

If the filter element is upstream of the second housing chamber, then particulate removal can be effected before dust can reach the sensor elements, protecting the delicate components in the second housing chamber. Advantageously, where the first housing chamber contains a particulate sensor, this allows for particulate capture to occur after the particulate sensing has occurred, so that accurate measurements can be made.

Optionally, the first and second end portions may each comprise an end cap locator and an end cap receivably engagable with the end cap locator.

Removable end caps of the device advantageously improve the ease with which cleansing of the device can occur.

The air inlet and air outlet may respectively be formed by a perimeter gap between the respective end cap locator and end cap of the first and second end portions.

A perimetric shadow gap limits the ingress of larger dust particles which could clog the device, as well as creating a uniform air flow around the perimeter. This uniformity can reduce the noise output by the device.

The electrically-energisable fan may be provided as a particulate sensor fan.

Where a particulate sensor is used, a fan will already be present. The air quality sensor device can thus be designed so that the fan of the particulate sensor is sufficiently powerful to drive air through the device. This reduces the size of the device, since no additional fan is required.

According to an eighth aspect of the invention, there is provided an air quality sensor device comprising: a housing having first and second opposed end cap locators, a first end cap engaged with the first end cap locator which defines an air inlet of the air quality sensor, and a second end cap engaged with the second end cap locator which defines an air outlet of the air quality sensor device; an electrically-energisable fan located in the housing for driving air between the air inlet and the air outlet; and at least one air quality sensor element mounted in the housing; at least one of the first and second end caps being removably engagable with the first and second end cap locators respectively to permit dust extraction.

Removability of opposed end caps for the device ensure that cleaning can occur relatively simply by an end user, reducing the risk of dust ingress into the delicate internal components of the device.

Preferably, the first and second end caps may each comprise a stem receivably engagable with a corresponding receiver of the first and second end cap locators, respectively.

The stem here acts as a partial plug which only allows a small air volume between the end cap and end cap locator to be passed through. This may reduce the air volume through the device which may allow a smaller fan, such as that of a particulate sensor, to be utilised.

The stem may include a recess via which a connector between the end cap and end cap locator is accessible.

A central recess for a locking element or similar fastener may be the best way of ensuring that a perimetric gap forming the air inlet can be used. This reduces noise, whilst also allowing easy access to the locking element which holds the end cap in place.

Optionally, the air inlet and air outlet may be respectively formed by a perimeter gap between the respective end cap locator and end cap.

A perimeter gap acting as an air inlet or air outlet reduces the noise produced by the device, compared with a device having a small aperture or set of apertures. The air quality sensor device is therefore comparatively unobtrusive.

The first end cap locator and first end cap may receivably engage with one another to form a baffle chamber within the air quality sensor device.

Rather than building a baffle chamber for air redirection into the main chamber of the device, the total volume can be reduced by forming the baffle chamber by the engagement between the first end cap and corresponding end cap locator.

According to a ninth aspect of the invention there is provided an air quality sensor device comprising: a housing having a plurality of longitudinal sides, a first geometric end cap defining an air inlet of the air quality sensor, and a second geometric end cap at an opposite end of the housing which defines an air outlet of the air quality sensor; an electrically-energisable fan located in the housing for driving air between the air inlet and the air outlet; and a circuit substrate including at least one air quality sensor element, the circuit substrate comprising a plurality of circuit substrate portions which are hingeably interconnected, the circuit substrate being foldably receivable within the housing to at least in part adopt a cross-sectional geometric shape of housing.

To maximise the use of space within the air quality sensor, which has the additional advantage of minimising the space in which air eddies or recirculation can occur, the electrical components can be stacked in a space-efficient manner. One way in which this can be achieved is by matching the number of circuit substrate portions to the number of longitudinal sides, and then folding the circuit substrate into a corresponding number of portions. This shape matching of the shape of the whole device ensures that all free surfaces fold together to form a central air channel, encouraging air flow in a linear manner through the device.

The air quality sensor device may be formed as a triangular prism.

A triangular prism is the correct shape for a three-board device, which is a logical construction due to the need to provide a processor board, a sensor board, and a communications board. The device is also very stable, due to the low centre-of-gravity.

Preferably, at least two of the plurality of circuit substrate portions may include a wireless antenna.

The construction of the circuit substrate is such that antenna can be positioned very easily so as to be angled relative to one another. In a preferred embodiment for communications, the circuit substrate portions would have antennae which are perpendicular to one another, for maximum signal coverage. The 60° angular arrangement of the circuit substrate portions of the triangular prism arrangement is also good for communication coverage.

Optionally, each circuit substrate portion may be positioned at or adjacent to one of the plurality of longitudinal sides.

The positioning of the circuit substrate portions is such that the air flow through the device is channelled in a mostly linear manner across the sensor elements. The air quality sensor device may further comprise a central support member which engages with the circuit substrate to hold the geometric shape.

The risk with a foldable substrate is that the structure moves during use, and thus, a dedicated central support member which allows, and can indeed improve, air flow through the device is extremely useful.

First and second end cap locators may be provided which are engagable with the central support member and which receive the respective first and second geometric end caps.

End cap locators are used to hold the end caps in place, and for structural stability, these may connect directly to the central support member to buttress the geometry of the air quality sensor device.

A plurality of said air quality sensors may be provided, the plurality of air quality sensors being provided on one circuit substrate portion.

According to a tenth aspect of the invention there is provided an air quality sensor device comprising: a housing having a plurality of longitudinal sides, a first end cap defining an air inlet of the air quality sensor, and a second end cap at an opposite end of the housing which defines an air outlet of the air quality sensor; an electrically-energisable fan located in the housing for driving air between the air inlet and the air outlet; and at least one sensor element mounted in the housing.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1A shows a top perspective representation of one embodiment of an in room air quality sensing apparatus in accordance with the first aspect of the invention, formed as a unitary air quality sensor device in accordance with the seventh aspect of the invention;

Figure 1B shows a bottom perspective representation of the in-room air quality sensing apparatus of Figure 1A;

Figure 2 shows an exploded perspective representation of the in-room air quality sensing apparatus of Figure 1A; Figure 3 shows a front perspective representation of a circuit substrate of the in room air quality sensing apparatus of Figure 1A;

Figure 4 shows a front perspective representation of the circuit substrate of Figure 3 including a central support member installed, the circuit substrate being in a part-folded condition;

Figure 5 shows a front perspective representation of the circuit substrate of Figure 4 in a fully folded condition;

Figure 6 shows a bottom perspective representation of the circuit substrate of Figure 7;

Figure 7 shows a front perspective representation of the circuit substrate of Figure 5, indicating the positions of end cap locators which interface with the central support member;

Figure 8 shows a bottom perspective representation of an inner circuit assembly of the in-room air quality sensing apparatus of Figure 1A;

Figure 9 shows a bottom perspective representation of the inner circuit assembly of Figure 8 being inserted into an outer housing of the in-room air quality sensing apparatus;

Figure 10 shows a front perspective representation of the in-room air quality sensing apparatus of Figure 1 A with the end caps removed;

Figure 11 shows a vertical cross-sectional representation through the in-room air quality sensing apparatus of Figure 1A;

Figure 12 shows a front perspective representation of the in-room air quality sensing apparatus of Figure 1A, with the outer housing removed, the circuit substrate in part-folded condition, and the front half of the apparatus shown in horizontal cross- section;

Figure 13 shows the in-room air quality sensing apparatus of Figure 12, with the block arrows showing an air flow path through the apparatus; Figure 14 shows the front perspective representation of the in-room air quality sensing apparatus of Figure 1A in horizontal cross-section; and

Figure 15 shows the in-room air quality sensing apparatus of Figure 14, with the block arrows showing an air flow path through the device and

Figure 16 shows a perspective representation of a building having an air quality control system in accordance with the second aspect of the invention.

Referring to Figures 1A and 1 B, there is indicated an in-room air quality sensing apparatus, referenced globally at 10, taking the form of an air quality sensor device which has an aesthetically appealing geometric profile. Here, the air quality sensor device 10 is provided in the form of a triangular prism, having a moulded outer housing 12 which presents a uniform outer surface of the device 10 along the longitudinal sides thereof.

The in-room air quality sensing apparatus 10 is configured to draw air into the housing 12 thereof for the purpose of sensing the gas composition, and, accordingly, provide command signals to other airflow control devices within a building or site.

At either end of the outer housing 12 is provided an end cap 14 which has a shape which matches that of the geometry of the outer housing 12, here, being triangular end caps 14. The end caps 14 are slightly spaced apart from the outer housing 12 at a rim thereof, to form a gap 16, known as a shadow gap, through which air can enter and exit the in room air quality sensing apparatus 10.

Figure 1 shows the first end cap 14 which forms the air inlet 18 of the in-room air quality sensing apparatus 10, whereas Figure 2 shows the second end cap 14 which forms the corresponding air outlet 20. Air flow would, from an exterior of the in-room air quality sensing apparatus 10, appear to flow linearly through the centre of the in-room air quality sensing apparatus 10. The actual flow path through the in-room air quality sensing apparatus 10 is discussed in more detail below, however. The first and second end caps 14, 16 are thus provided at either end of the housing 12, thereby defining the perimetric air inlet 18 and air outlet 20, respectively.

Figure 2 shows the bottom of the in-room air quality sensing apparatus 10. The in-room air quality sensing apparatus 10 is intended to rest on one of the longitudinal sides of the outer housing 12, and this can be predefined by the manufacturer by the provision of one or more support elements, such as the feet 22 illustrated. These could be integrally moulded with the outer housing 12, or more preferably be provided as, for example, rubberised elements which provide additional grip for the air quality sensor device 10 when resting on another surface.

A power inlet 24 is also provided, which may allow for a wired connection for in-room air quality sensing apparatus 10. This in-room air quality sensing apparatus 10 is likely to be a comparatively heavy-duty air quality sensor device 10, and thus may not be a particularly portable unit. A wired connection is therefore preferred.

The internal componentry of the in-room air quality sensing apparatus 10 is shown in Figure 2. In the centre of the in-room air quality sensing apparatus 10, there is an inner casing 26 which is substantially the same shape as the outer housing 12, and which, in conjunction with a central support member 28, supports the circuit substrate 30 to which the electrical components of the in-room air quality sensing apparatus 10 are mounted.

The main electrical component is an electrically-energisable fan 32 which serves to drive air through the in-room air quality sensing apparatus 10, and which is provided with a dedicated cover 34 to serve to direct airflow accordingly.

The inner frame 26 is sealed using first and second end cap locators 36a, 36b which are respectively associated with the end caps 14 of the air inlet 18 and air outlet 20. The end cap locators 36a, 36b engage with the central support member 28, preferably via an interference fit, and sealingly close the inner frame 26 to form a housing chamber therein.

Each end cap locator 36a, 36b comprises a receiver portion 38 into which a stem 40 of each end cap 14 is insertable. A rotatable locking connector 42 may be provided to ensure the connection between the end cap 14 and end cap locator 36a, 36b, which in the present embodiment, can be accessed through a central recess 44 of each end cap 14 and turned using a geometric key, such as a hex key or similar tool.

A sealing element 46 is provided at an interface between each end cap 14 and the respective locator 36a, 36b in order to provide suitable control over the airflow therethrough. A dedicated filter 48 is provided upstream of the end cap locator 36a at the air inlet 16 in an attempt to limit large particulate ingress into the air quality sensor device 10.

Each end cap 14 and associated end cap locator 36a, 36b can be considered to form an end portion 50 of the air quality sensor device 10. The first and second end cap locators 36a, 36b preferably create a baffle system within the housing 12, which ensures that the airflow path within the housing 12 between the air inlet 18 and the air outlet 20 follows an expected and predetermined route.

The electrically energisable fan 32 is here formed as part of a particulate sensor, which provides one form of sensing capability for the in-room air quality sensing apparatus 10. This is mounted to a circuit substrate 30, which is here formed as a multi-part, foldable circuit substrate.

Figure 3 shows the circuit substrate 30 in detail. The circuit substrate 30 is here provided as hinged or foldable circuit substrate having a plurality of circuit substrate portions 30a, 30b, 30c which are pivotably engagable with one another. The circuit substrate 30 can thus be folded into the correct geometric configuration to be received into the air quality sensor device 10 so that each circuit substrate portion 30a, 30b, 30c extends along, or extends in parallel with, the longitudinal sides of the air quality sensor device 10.

The first circuit substrate portion 30a comprises at least one, and preferably a plurality of air quality sensors 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i. Here, there is a carbon dioxide sensor element 52a, and a plurality of complementary sensor packages 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i arranged in a grid on the rigid circuit board of the first circuit substrate portion 30a.

A plurality of air quality sensors 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i , also referred to as air quality sensor elements, on the first substrate portion 30a thereby forms a dedicated air quality sensing region on the airflow path within the housing 12. This can be best visualised from Figure 3. The plurality of air quality sensors 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i comprises at least first and second different air quality sensors 52a, 52b, designed to primarily monitor different gases within the air. Additional different air quality sensors 52c, 52d, 52e, 52f, 52g, 52h, 52i, for sensing different primary gases, are also provided, for a total of nine different gas sensor packages in the depicted embodiment.

Sensor packages which form air quality sensors 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i are not, however, gas specific. Each air quality sensor 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i has a primary sensing function, which may or may not be indicative of the gas to which it is most responsive. For example, ozone sensors are known, as are carbon dioxide sensors, carbon monoxide sensors, nitrogen oxide sensors, and so on. Each of these sensors exhibits sensitivity towards at least one other gas. This characteristic is known as cross-sensitivity.

Sensor packages output a sensor output in the form of a readable current, based on the gas measured at the sensor.

An ozone sensor will be primarily designed for the purpose of sensing ozone in the atmosphere, but will also exhibit a strong response to hydrogen sulphide and chlorine in the atmosphere, as well as more moderate responses to methane, nitrogen dioxide, carbon monoxide, and n-heptane.

The expected sensor output from the ozone sensor can thus be defined as follows: sOs = a.[0₃] + b.[CH₄] + C.[N0₂] + d.[H₂S] + e.[CO] + f.[CI₂] + g.[C₇H₁₆]

On the other hand, a hydrogen sulphide sensor will be primarily designed for the purpose of sensing hydrogen sulphide. It experiences moderate responses to methane, ammonia, nitrogen dioxide, carbon monoxide, ozone, sulphur dioxide, nitric oxide, chlorine, and n- heptane.

SH₂S = h.[CH₄] + i.[NH₃] + j.[N0₂] + k.[CO] + l.[0₃] + m.[S0₂] + n.[NO] + o.[CI₂] + p.[C₇H₁₆]

The cross-sensitivity parameters a to p in these simultaneous equations are typically provided within the manufacturer’s instructions, and thus can be programmed readily into a processor 53 of the in-room air quality sensing apparatus 10. Linear equations, non linear equations, or machine learning techniques could all be used to resolve the mathematical issues here. Of course, processing could be readily achieved using offboard processors, for example, via cloud computing.

Using only values s0₃ and sH₂S as sensor outputs, it is not possible to completely and accurately identify which gases are contributing to signal changes; however, educated inferences can be made. For example, chlorine is not typically found in the air in appreciable concentrations, and therefore may be treated as a baseline reading. By limiting the simultaneous equations in this manner, changes in the signal outputs of two air quality sensors 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i may provide an indication of atmospheric gas changes for more than two gases.

Of course, the more simultaneous equations that can be generated, the more accurate the determination of any changes to gas concentration over a wide variety of different gases, by solving the simultaneous equations for each air quality sensor 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i. This may allow for the determination of the concentrations, and more critically, changes to the concentrations, of the gas components of the air passed along the airflow path. Nine air quality sensors 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i are provided in the depicted embodiment in Figure 3, all of which are communicable with the onboard processor 53 to allow onboard determination of the gas concentrations on the airflow path for a plurality of different gases.

The air quality sensors 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i are well-packed onto the first circuit substrate portion 30a, which is important, though not absolutely critical, for sampling the same gas at the same time on the airflow path.

The air quality sensors 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i are preferably gas sensors, but particulate sensors or water sensors could be utilised as well. The gas sensors will typically be electrochemical sensors.

Whilst the manufacturer’s datasheets may provide detailed information about the sensor packages, there will be some tolerances. As such, it may be preferable to calibrate the in-room air quality sensing apparatus 10 to determine the device-specific cross sensitivity parameters for each air quality sensor 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i. This can be achieved by altering the concentrations of gas components within a gas sample provided to the in-room air quality sensing apparatus 10 during calibration; with known gas concentrations, the device-specific cross-sensitivity parameters can be calculated by solving the simultaneous equations.

Processing of the data from the air quality sensors 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i can therefore be performed in real-time by an onboard processor 38, leading to rapid determination of air quality.

The second circuit substrate portion 30b comprises additional electronic components, such as communications elements 54, which allows forwireless communication between the air quality sensor device 10 and other connected devices. Such connected devices could include air filtration or ventilation devices within a building or area which may be controlled via the air quality sensor device 10.

Temperature and/or pressure sensors 55a, 55b may be provided inside the housing 12 for the purpose of calibrating the air quality sensors 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i. The manufacturer’s datasheets provide detailed information as to how the signal output for each air quality sensor 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i may change in response to the environmental conditions.

The circuit board of the second circuit substrate portion 30b here includes a locator tab 56 which assists with connection to the central support member 28 once installed. Such a tab could be provided on any of the circuit substrate portions for this reason.

The third circuit substrate portion 30c may comprise a further communications element 58. The geometric configuration of the folded circuit substrate 30 may thus improve the wireless connectivity of the air quality sensor device 10, since the longitudinal sides of the air quality sensor device 10 will be at 60° angles to one another, if an equilateral triangular prism geometry is chosen. This will ensure that there will be reasonable antenna pick-up regardless of the orientation of the air quality sensor device 10.

The third circuit substrate portion 30c more importantly supports the electrically energisable fan 32, which could in fact be provided as the fan of a particulate sensor in order to improve the utility of the air quality sensor device 10.

A moulded cover 34 for the electrically energisable fan 32 is dimensioned to control the air inflow and exhaust to and from the electrically energisable fan 32. An exhaust channel 60 is provided for directing air out of the fan 32, and an elongate inlet channel 62 is provided which connects to the air inlet 18 of the air quality sensor device 10 to ensure that there is no other air ingress to the main housing chamber other than via the electrically energisable fan 32. The elongate inlet channel 62 is not visible in Figure 3, but can be seen in Figure 12. An additional seal 64 may be provided to ensure this sealing is effective.

The hinges of the circuit substrate 30 are preferably provided as circuit flexes 66 which permit electrical communication between the plurality of circuit substrate portions 30a, 30b, 30c. It will be appreciated that the circuit substrate could be formed as a flexible circuit substrate or similar flexible printed circuit board, or alternatively flexible wired connections could be provided between adjacent circuit substrate portions.

The engagement of the central support member 28 with the circuit substrate 30 is shown in Figure 4. The central support member 28 is constructed as a central hub portion 68 from which extends three support arms 70a, 70b, 70c. The first support arm 70a engages with the locator tab 56 via an anchor portion 72a, whilst an end 72b of the second support arm 70b effectively hooks around the second circuit substrate portion 30b, and will hook onto the edge of the first circuit substrate portion 30a once it is raised. The first and third circuit substrate portions 30a, 30c can both be raised into place to clip into place with a retaining member 72c of the third support arm 70c. This assembled configuration is shown in Figures 5 and 6.

The circuit substrate 30 and central support member 28, once assembled, form the core of an inner circuit assembly 74, as shown in Figure 7, in conjunction with the end cap locators 36a, 36b. The structure of the end cap locators 36a, 36b is shown in more detail in Figure 8.

The first end cap locator 36a has an elongate opening 76 which acts as the passage from the gap 16 forming the air inlet 18 to the electrically-energisable fan 32. The elongate seal 64 is provided to connect the elongate opening 76 with the elongate inlet channel 62 of the cover 34 for the electrically energisable fan 32. There is also a port 78 in the first end cap locator 36a which connects with the exhaust channel 60 so that air expelled from the electrically-energisable fan can pass back through the first end cap locator 36a and into a baffle chamber formed between the first end cap locator 36a and the corresponding end cap 14. A corresponding seal 80 is then provided which couples between the exhaust channel 60 and the port 78.

The second end cap locator 36b has a plurality of spaced apart exit vents 82 around the outer portion thereof, which allow venting from the inside of the inner circuit assembly 74 in a uniform or substantially uniform manner.

Each end cap locator 36a, 36b includes a seal seat 84, which is formed as a triangular seat for a triangular seal 46, in a body thereof. This delineates between an outer portion 86 of the end cap locator 36a, 36b, which forms the air inlet 18 or air outlet 20 with the corresponding end cap 14, and an inner volume which is enclosed by the receiver portion 38 of the end cap locators 36a, 36b.

The inner circuit assembly 74 is then completed by the addition of the inner casing 26, as per Figure 8, which preferably has first and second casing portions 26a, 26b to form a full side shell around the circuit substrate 30. The inner casing 26 may have one or more clips or connectors 88 which engage with the end cap locators 36a, 36b. As can be seen, the retaining member 72c may be configured to abut against the first casing portion 26a to provide additional structural rigidity.

Figure 9 shows the inner circuit assembly 74 being inserted into the outer housing 12, so as to fit snugly inside the inner volume 90 of the outer housing 12. The power inlet 24 may be provided as a separate component, and fasteners 92 of the power inlet 24 may serve to lock the relative longitudinal positions of the inner circuit assembly 74 and the outer housing 12.

To finally assemble the air quality sensor device 10, the end caps 14 are attached. This can be seen in Figure 10. The stems 40 are inserted into the receiver portions 38 of the first and second end cap locators 36a, 36b, and a rotatable locking connector 42 can lock into position in either the end cap locators 36a, 36b or central support member 28. An elongate hex key or screwdriver might be suited towards access through the central recess 44 of the end caps 14 to turn the rotatable locking connector 42.

The filter element 48 may be provided which engages with the stem 40 of an end cap so as to be receivable in, in this instance, the receiver portion 38 of the first end cap 36a. The filter element 48 fills a large volume within the baffle chamber 94 formed between the end cap 14 and the first end cap locator 36a, and this can be seen in detail in Figure 12.

Figure 11 illustrates how the air flow variation is achieved using the sealing at the first end cap locator 36a. Air enters the air inlet 18 all around the shadow gap 16, but cannot bypass the triangular seal 46. The only access into the air quality sensor device 10 for said air is through the elongate inlet channel 62 into the first chamber 96 in which the electrically energisable fan 32 is located.

The triangular seal 46 by extension creates an inner volume which is sealed off from the outer portion of the end cap locator 36a. As noted above, this forms a baffle chamber 94 within which the filter element 48 is seated. The baffle chamber 94 acts as an intermediate air flow chamber between the first housing chamber 96 and the main, second housing chamber 98 which houses the circuit substrate 30.

The engagement between the central support member 28 and the end cap locators 36a, 36b can be seen in more detail in Figure 11. The end cap locators 36a, 36b each have connector members 100 which engage with corresponding connectors 102 located in the hub portion 68 of the central support member 28.

Internal substrate holders 104 of the inner casing 26 can also be seen in Figure 11, formed as hooked receivers which receivably engage the edges of the circuit substrate portions 30a, 30b, 30c.

The air flow path leading to and from the baffle chamber 94 can be seen in more detail in Figures 12 and 14, and via the corresponding block arrows in Figures 13 and 15. Air enters through the gap 16 of the air inlet 18, and enters the elongate inlet channel 62, drawn through by the electrically energisable fan 32 in the first housing chamber 96. There is no direct air path into the second housing chamber 98.

The exhaust channel 60 of the first housing chamber 96 connects to an inlet on the first end cap locator 36a, so that air exits the electrically-energisable fan 32 directly into the baffle chamber 94. The air is immediately filtered by the filter element 48, preventing large particulate matter from coming into contact with the downstream sensor elements 52a, 52b. The advantage of this construction is that, if the electrically energisable fan 32 is that of a particulate sensor, then the filtration occurs downstream of the particulate sensor, thereby enabling accurate reading of the particulate content, but upstream of the more sensitive sensor elements 52a, 52b.

The outlets 106 of the baffle chamber 94 are provided on at least one, and preferably more than one, side wall 108 of the first end cap locator 36a which are spaced apart from the first housing chamber 96. The baffle chamber 94 thus serves as an airflow director which channels the air from the fan 32 backwards through the device 10, so that the air can pass in a near linear fashion through the second housing chamber 98. In essence, the baffle chamber 94 provides a turning motion to the air passing through.

This effectively results in air exiting the baffle chamber 94 at one end of the second housing chamber 98 which is opposite to the air outlet 20 of the air quality sensor device 10. Air can thus flow from a first end portion of the air quality sensor device 10 to a second opposite end portion thereof. This creates linear air flow across the circuit substrate portions 30a, 30b adjacent to the outlets 106, avoiding the recirculation effects which can otherwise hamper air quality sensing equipment. Once linear flow is achieved, air can exit the air quality sensor device 10 through the exit vents 82 of the second end cap locator 36b, and out of the air outlet 20.

The wireless communications element 54 which is in communication with the processor 53, and preferably which has an operational frequency of less than 1 GHz. This allows the in-room air quality sensing apparatus 10 to communicate with and provide command and control signals to other air control devices which create airflow within a location. The communications frequency is suitable for transmission through communications- disrupting structures at a site, such as steel beams or thick stone walls, which allows the in-room air quality sensing apparatus 10 to be used on such sites for the purposes of centralised airflow control.

The provision of wireless communications of course allows for the option of decentralised processing, in which the data from the air quality sensors 52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i is performed externally to the in-room air quality sensing apparatus 10.

The in-room air quality sensing apparatus 10 thus provides a means of improving the control of an air quality control system for a building 110, such as that shown in Figure 16. The in-room air quality sensing apparatus 10 is the control unit for all of the airflow control devices around the building 110.

Each airflow control device includes a housing having an air inlet and an air outlet, an electrically-energisable fan which is configured to create an airflow path from the air inlet to the air outlet, a wireless communication element communicable with the wireless communication element of the in-room air quality sensing apparatus 10 to receive a command signal therefrom, and a processor in communication with the wireless communication element. The processor is configured to control the electrically- energisable fan of each airflow control device in response to the command signal from the in-room air quality sensing apparatus 10. Each airflow control device may be tagged in some way which is indicative of its location within the building 110, and thus provides the in-room air quality sensing apparatus 10 with additional context when providing said command signal.

Examples of airflow control devices include freestanding in-room air filters 112, 114, positive input ventilation units 116, ceiling or wall-mounted air filters 118, and extractor fans 120. These may be positioned in different rooms in the building 110, controlling the airflow separately. The in-room air quality sensing apparatus 10 thus allows for statistical or holistic ventilation control, in that a centralised sensing apparatus 10 can command the airflow created by airflow control devices in a building 110 based on highly accurate gas concentration measurements.

Crucially, the identification of which gas components are changing may provide an indication of where in the building 110 the ventilation must be improved. Ammonia readings will be larger in bathrooms or lavatories, and if the in-room air quality sensing apparatus 10 senses ammonia spikes, then bathroom-located airflow control devices may be activated in preference to other airflow control devices. Equally, carbon monoxide may be a more prevalent gas released from heating sources, such as stoves or boilers, and therefore ventilation in the appropriate area could be controlled as a result.

The in-room air quality sensing apparatus 10 need not necessarily only be the controller for other airflow control devices, but could equally be provided with control over, for instance, windows and doors within the building 110 for airflow manipulation. Similarly, the in-room air quality sensing apparatus 10 could link into existing airflow directing architecture of a building, such as ventilation ducting, to provide more powerful airflow control. The system could also be linked to a heating system of the building, to thereby allow for mutual control.

Whilst an in-room air quality sensing device having a dedicated housing with an internal airflow path is shown, it will be appreciated that an apparatus using cross-sensitivity information could readily be provided within the scope of the present inventive concept. In such a scenario, a sealed housing could be provided, having no inlet or outlet, and no fan would be necessary.

Furthermore, whilst an onboard processor is suitable for the determination of the gas concentrations, it will be appreciated that an external processor, for example, a cloud- based processor, or one based on a smartphone app, could be provided to achieve the same end without needing an onboard processor to perform the calculations.

It will also be clear that sensing need not necessarily be confined to a single device, and cross-sensitivity measurements could be conducted based on readings from several different discrete sensor locations. This leads to an in-room air quality sensing system having a plurality of discrete in-room air quality sensing apparatuses which are communicatively coupled to one another. This could thus be configured such that the system as a whole is linked to a server via wired or wireless broadband or cellular connections, or via a radio mesh network, for instance. Individual devices could act as wireless bridges connecting the local radio network to the domestic or building Wi-Fi (RTM) network.

It will be clear that, although a triangular prism shape has been chosen for, particularly but not necessarily exclusively, aesthetic purposes, other geometric configurations are feasible, such as cuboid, pentagonal prism, or hexagonal prism, by way of example only.

It is therefore possible to provide an in-room air quality sensing apparatus which is capable of utilising the natural cross-sensitivities of commercially available air quality sensors in a compact arrangement, so that detailed, real-time gas concentration information can be easily obtained for a wide range of different potential gases in the local atmosphere. This apparatus then allows for the creation of a holistic or statistical gas sensing regime to be achieved, enabling more powerful ventilation control systems to be considered within domestic, commercial, and industrial buildings and sites.

It is therefore also possible to provide a compact air quality sensor device having a geometry which not only facilitates the air flow through the device, and particularly across the sensors, but which has a novel circuit board configuration to minimise the volume of the device once assembled. The use of removable end caps at either end of the device also improves the ease with which a user can access and clean dust filters thereof.

The words ‘comprises/comprising’ and the words ‘having/including’ when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps, or components, but do not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

The embodiments described above are provided by way of examples only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined herein.

Claims

1. An in-room air quality sensing apparatus (10) comprising: a housing (12) having an air inlet (18) and an air outlet (20); an electrically-energisable fan (32) which is configured to create an airflow path from the air inlet (18) to the air outlet (20); a first air quality sensor (52a) mounted on the airflow path having a primary gas sensitivity for a first gas and a secondary gas sensitivity for a second gas, the first air quality sensor (52a) producing a first sensor output; a second air quality sensor (52b) mounted on the airflow path having a primary gas sensitivity for a third gas and a secondary gas sensitivity for the said second gas, the second air quality sensor (52b) producing a second sensor output; and a processor (53) in communication with the first and second air quality sensors (52a, 52b) to receive the first and second sensor output signal therefrom, the processor (53) being configured to calculate gas concentrations for each of the first, second, and third gases.

2. An in-room air quality sensing apparatus (10) as claimed in claim 1, wherein the processor 953) is configured to calculate the gas concentrations based on any or all of: a plurality of linear equations; a plurality of non-linear equations; and machine learning.

3. An in-room air quality sensing apparatus (10) as claimed in claim 1 or claim 2, wherein the first and second air quality sensors (52a, 52b) are adjacent to one another within the housing (12) on the airflow path.

4. An in-room air quality sensing apparatus (10) as claimed in any one of the preceding claims, wherein the first and second air quality sensors (52a, 52b) are mounted to the same circuit substrate (30) within the housing (12).

5. An in-room air quality sensing apparatus (10) as claimed in any one of the preceding claims, further comprising a wireless communication element (54) in communication with the processor (53), the wireless communication element (54) having a communication frequency of less than 1GHz.

6. An in-room air quality sensing apparatus (10) as claimed in any one of the preceding claims, wherein the air inlet (18) and air outlet (20) are at opposite ends of the housing (12).

7. An in-room air quality sensing apparatus (10) as claimed in any one of the preceding claims, wherein the processor (53) is an onboard processor.

8. An in-room air quality sensing apparatus (10) as claimed in any one of claims 1 to 6, wherein the processor is an external processor.

9. A method of calibration of an in-room air quality sensing apparatus (10) as claimed in any one of the preceding claims, the method comprising the steps of: a] passing a gas mixture along the airflow path having a known concentration of the first gas; a known concentration of the second gas; and a known concentration of the third gas; and b] calibrating the first and second sensor output signals based on the calculated gas concentrations of the first, second and third gases by the processor.

10. An air quality sensing system comprising: a plurality of different air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i); and a processor (53) in communication with the plurality of air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i), the processor (53) being configured to calculate gas concentrations for a plurality of different gases based on cross sensitivities of the plurality of different air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i).

11. An air quality sensing system as claimed in claim 10, wherein the plurality of different air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) is provided as part of an in-room air quality sensing apparatus (10) having an airflow path therethrough.

12. An air quality sensing system as claimed in claim 11 , wherein there are at least three different air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) mounted on the airflow path.

13. An air quality sensing system as claimed in claim 11 or claim 12, further comprising a housing (12) having an air inlet (18) and an air outlet (20), and an electrically energisable fan (32) which is configured to create the airflow path from the air inlet (18) to the air outlet (20).

14. An air quality sensing system as claimed in claim 13, wherein the plurality of different air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) is mounted on a single circuit substrate (30) within the housing (12).

15. An air quality sensing system as claimed in any one of claims 10 to 14, wherein a plurality of said processors (53) is provided.

16. An air quality control system comprising: an in-room air quality sensing apparatus (10) including: a housing (12) having an air inlet (18) and an air outlet (20); an electrically-energisable fan (32) which is configured to create an airflow path from the air inlet (18) to the air outlet (20); at least one air quality sensor (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) mounted on the airflow path; a first processor (53) in communication with the at least one air quality sensor (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) to receive a sensor output signal therefrom, the first processor (53) being configured to generate a command signal based on the sensor output signal; a first wireless communication element (54) in communication with the processor (53); and a plurality of airflow control devices, each device including: a housing having an air inlet and an air outlet; an electrically-energisable fan which is configured to create an airflow path from the air inlet to the air outlet; a second wireless communication element communicable with the wireless communication element of the in-room air quality sensing apparatus to receive the command signal therefrom; a second processor in communication with the wireless communication element, the second processor being configured to control the electrically-energisable fan of the airflow control device in response to the command signal.

17. An air quality control system as claimed in claim 16, wherein the in-room air quality sensing apparatus (10) includes a plurality of said air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i).

18. An air quality control system as claimed in claim 17, wherein the processor of the in-room air quality sensing apparatus (10) is configured to calculate gas concentrations for a plurality of different gases on the airflow path based on cross-sensitivities of the plurality of different air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i).

19. An air quality control system as claimed in any one of claims 16 to 18, wherein the first wireless communication element (54) and the second wireless communication element have a communication frequency of less than 1GHz.

20. An air quality control system as claimed in any one of claims 16 to 19, wherein the plurality of airflow control devices comprises at least one of: an in-room air filter (112, 114, 118); an extractor fan (120); and a positive input ventilation unit (116).

21. An air quality control system as claimed in any one of claims 16 to 20, wherein each of the plurality of airflow control devices is provided in a different location.

22. An air quality control system as claimed in any one of claims 16 to 21 , wherein the first processor (53) is configured to generate an airflow-control-device-specific command signal based on the sensor output signal, depending on a location of each of the plurality of airflow control devices.

23. An air quality control system comprising: an in-room air quality sensing apparatus (10) including: at least one air quality sensor (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) mounted on the airflow path; a processor (53) in communication with the at least one air quality sensor (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) to receive a sensor output signal therefrom, the processor (53) being configured to generate a command signal based on the sensor output signal; a wireless communication element (54) in communication with the processor, the wireless communication element (54) having a communication frequency of less than 1GHz; and at least one airflow control device including: a housing having an air inlet and an air outlet; an electrically-energisable fan which is configured to create an airflow path from the air inlet to the air outlet; a wireless communication element communicable with the wireless communication element of the in-room air quality sensing apparatus to receive the command signal therefrom, the wireless communication element having a communication frequency of less than 1GHz; a processor in communication with the wireless communication element, the processor being configured to control the electrically- energisable fan of the airflow control device in response to the command signal.

24. A method of installing a providing air quality control in a building or site having communications-disrupting structures, the method comprising the steps of: a] providing an air quality control system as claimed in claim 23; and b] configuring the in-room air quality sensing apparatus (10) and at least one airflow control device to communicate to one another at a communication frequency of less than 1GHz.

25. An air quality sensor device (10) comprising: a housing (12) having a first end portion (50) having an air inlet (18), a first housing chamber, a second housing chamber, and a second end portion (50) which is opposite the first end portion and having an air outlet (20); an electrically-energisable fan (32) located in the first housing chamber which is configured to create an air flow path from the air inlet (18), through the first housing chamber, into the second housing chamber, and to the air outlet (20); an airflow director which directs air from the first housing chamber into the second housing chamber so as to enter the second housing chamber at or adjacent to the first end portion (50); and at least one air quality sensor element (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) mounted in the second housing chamber on the air flow path; the air flow path extending through the second housing chamber from the first end portion (50) to the second end portion (50).

26. An air quality sensor device (10) as claimed in claim 25, wherein the at least one air quality sensor element (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) is mounted at or adjacent to a longitudinal side of the housing (12).

27. An air quality sensor device (10) as claimed in claim 26, wherein a plurality of said air quality sensor elements (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) is provided.

28. An air quality sensor device (10) as claimed in any one of claims 25 to 27, wherein the first end portion includes a baffle chamber positioned on the air flow path between the first and second housing chambers, the baffle chamber forming the airflow director.

29. An air quality sensor device (10) as claimed in claim 28, further comprising a filter element receivable in the baffle chamber upstream of the second housing chamber.

30. An air quality sensor device (10) as claimed in any one of claims 25 to 29, wherein the first and second end portions each comprise an end cap locator (36a, 36b) and an end cap (14) receivably engagable with the end cap locator (36a, 36b).

31. An air quality sensor device (10) as claimed in claim 30, wherein the air inlet (18) and air outlet (20) are respectively formed by a perimeter gap between the respective end cap locator (36a, 36b) and end cap (14) of the first and second end portions (50).

32. An air quality sensor device (10) as claimed in any one of claims 25 to 31 , wherein electrically-energisable fan (32) is provided as a particulate sensor fan.

33. An air quality sensor device (10) comprising: a housing (12) having first and second opposed end cap locators, a first end cap (14) engaged with the first end cap locator (36a) which defines an air inlet (18) of the air quality sensor, and a second end cap (14) engaged with the second end cap locator (36b) which defines an air outlet (20) of the air quality sensor device (10); an electrically-energisable fan (32) located in the housing for driving air between the air inlet (18) and the air outlet (20); and at least one air quality sensor element (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) mounted in the housing (12); at least one of the first and second end caps (14) being removably engagable with the first and second end cap locators (36a, 36b) respectively to permit dust extraction.

34. An air quality sensor device (10) as claimed in claim 33, wherein the first and second end caps (14) each comprise a stem (40) receivably engagable with a corresponding receiver of the first and second end cap locators (36a, 36b), respectively.

35. An air quality sensor device (10) as claimed in claim 34, wherein the stem includes a recess via which a connector (42) between the end cap (14) and end cap locator (36a, 36b) is accessible.

36. An air quality sensor device (10) as claimed in any one of claims 33 to 35, wherein the air inlet (18) and air outlet (20) are respectively formed by a perimeter gap (16) between the respective end cap locator (36a, 36b) and end cap.

37. An air quality sensor device (10) as claimed in any one of claims 33 to 36, wherein the first end cap locator (36a) and first end cap (14) receivably engage with one another to form a baffle chamber within the air quality sensor device (10).

38. An air quality sensor device (10) comprising: a housing (12) having a plurality of longitudinal sides, a first geometric end cap defining an air inlet (18) of the air quality sensor, and a second geometric end cap at an opposite end of the housing which defines an air outlet (20) of the air quality sensor; an electrically-energisable fan (32) located in the housing (12) for driving air between the air inlet (18) and the air outlet (20); and a circuit substrate (30) including at least one air quality sensor element (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i), the circuit substrate (30) comprising a plurality of circuit substrate portions (30a, 30b, 30c) which are hingeably interconnected, the circuit substrate (30) being foldably receivable within the housing (12) to at least in part adopt a cross-sectional geometric shape of housing (12).

39. An air quality sensor device (10) as claimed in claim 38, wherein the air quality sensor device (10) is formed as a triangular prism.

40. An air quality sensor device (10) as claimed in claim 38 or claim 39, wherein at least two of the plurality of circuit substrate portions (30a, 30b, 30c) include a wireless antenna.

41. An air quality sensor device (10) as claimed in claim any one of claims 38 to 40, wherein each circuit substrate portion (30a, 30b, 30c) is positioned at or adjacent to one of the plurality of longitudinal sides.

42. An air quality sensor device (10) as claimed in claim any one of claims 38 to 41, further comprising a central support member (28) which engages with the circuit substrate (30) to hold the geometric shape.

43. An air quality sensor device (10) as claimed in claim 42, further comprising first and second end cap locators (36a, 36b) engagable with the central support member (28) and which receive the respective first and second geometric end caps (36a, 36b).

44. An air quality sensor device (10) as claimed in any one of claims 38 to 43, wherein a plurality of said air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) is provided, the plurality of air quality sensors (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) being provided on one circuit substrate portion (30a).

45. An air quality sensor device (10) comprising: a housing (12) having a plurality of longitudinal sides, a first end cap (36a) defining an air inlet (18) of the air quality sensor device (10), and a second end cap (36b) at an opposite end of the housing which defines an air outlet (20) of the air quality sensor device (10); an electrically-energisable fan (32) located in the housing (12) for driving air between the air inlet (18) and the air outlet (20); and at least one sensor element (52a, 52b, 52c, 52d, 52e, 52f, 52g, 52h, 52i) mounted in the housing (12).