Wearable air purifier

Abstract

A wearable air purifier 10 comprising headgear 12 for wearing on a wearer’s head, a fan assembly 14 operable to generate an airflow, and a ducting arrangement 22 configured to receive the airflow from

Description

BACKGROUND Air pollution is a well-known problem, particularly in urban areas and in public spaces where space between individuals may be limited, such as on public transport. A variety of air pollutants, such as toxic gases and other particulates such as dust and pollen have known or suspected harmful effects on human health. As such, the use of personal protective equipment, such as face masks, is becoming more popular in urban areas and public spaces. A basic face mask may comprise one or more layers of a filtering material, such as a fabric, held over the mouth and / or nose of a wearer by an elastic strap. However, such face masks usually rely on passive filtration and their effectiveness is limited. More sophisticated approaches now exist, for example involving the use of a wearable air purifier which provides a filtered airflow to the face of a wearer. An example of a wearable air purifier is disclosed in GB2595231A to Dyson Technology Limited. Portability is an important feature of wearable air purifiers, and such purifiers therefore typically comprise a battery for powering the device. The battery inherently loses charge powering the wearable air purifier during use, and for continued use of the purifier the battery must be recharged. However, charging electronics of the wearable air purifier may get hot when operated to charge the battery, particularly because an air purifier is typically stationary during charging. Increased heat experienced by the charging electronics could result in mechanical stresses, performance loss, increased resistance and sub-optimal charging performance. It is against this background that the invention has been devised. SUMMARY In a first aspect of the present invention there is provided a wearable air purifier. The wearable air purifier comprises headgear for wearing on a wearer’s head, a fan assembly operable to generate an airflow, and a ducting arrangement configured to receive the airflow from the fan assembly and direct the airflow towards the wearer’s face. The wearable air purifier further comprises a battery to supply electrical power to the fan assembly, and charging electronics to supply electrical power to the battery to charge the battery. The charging electronics are thermally coupled to airflow in the ducting arrangement. The wearable air purifier further comprises a controller connected to the charging electronics and to the fan assembly. The controller is configured to detect operation of the charging electronics and to operate the fan assembly to generate airflow in the ducting arrangement based on the detected operation of the charging electronics. Operation of the fan assembly to generate an airflow that is thermally coupled to the charging electronics may help to cool the charging electronics, thereby reducing thermal cycling of the charging electronics, preventing overheating of the charging electronics, and increasing the longevity of the charging electronics. It will be appreciated that “thermally coupled” comprises both direct and indirect thermal coupling of the charging electronics to the airflow within the ducting arrangement. For example, the airflow in the ducting arrangement may flow directly over the charging electronics, and the charging electronics may therefore be directly thermally coupled to the airflow. In some other examples, the airflow in the ducting arrangement may flow over or against a heatsink arrangement that is thermally coupled to the charging electronics, and the charging electronics may therefore be indirectly thermally coupled to the airflow in the ducting arrangement. Ultimately, “thermally coupled” indicates that temperature of the charging electronics is influenced by the temperature of the “thermally coupled” airflow. As used herein, “charging electronics” refers to electrical components in the wearable air purifier which are involved in charging the battery of the wearable air purifier. For example, the charging electronics may comprise components such as fuses and / or a power management unit and associated series components such as a connector (for example a USB C connector), and / or a Positive Temperature Coefficient fuse (PTC), and / or an upstream protection device. In some examples, the wearable air purifier may further comprise a charging electronics parameter sensor for measuring a parameter of the charging electronics. The controller may be connected to the charging electronics parameter sensor. The controller may be configured to operate the fan assembly to generate airflow in the ducting arrangement based on both the detected operation of the charging electronics and the measured parameter of the charging electronics. Accordingly, in some examples the controller may be configured to avoid unnecessary power consumption by preventing unnecessary operation of the fan assembly based on the measured parameter of the charging electronics, thereby also reducing unnecessary acoustic noise generation. In some examples, the controller may be configured to determine if the measured parameter of the charging electronics meets a threshold. Further, the controller may be configured to subsequently operate the fan assembly to generate airflow in the ducting arrangement in response to a determination that the measured parameter meets the threshold and based on the detected operation of the charging electronics. Accordingly, in some examples the controller may perform a two-factor test before operating the fan assembly to generate airflow in the ducting arrangement. In some examples, the charging electronics parameter sensor may comprise a temperature sensor operable to measure a temperature of the charging electronics. Additionally or alternatively, in some examples the charging electronics parameter sensor may comprise a resistance sensor operable to measure a resistance in the charging electronics. In some examples, the battery may be thermally coupled to airflow generated by the fan assembly. As previously, described, “thermally coupled” comprises both direct and indirect thermal coupling. As such, in some examples the airflow within the duct may flow directly over battery, and the battery may therefore be directly thermally coupled to the airflow. In some other examples, the airflow within the duct may flow over or against a heatsink arrangement that is thermally coupled to the battery, and the battery may therefore be indirectly thermally coupled to the airflow in the duct. Ultimately, “thermally coupled” indicates that temperature of the battery is influenced by the temperature of the “thermally coupled” airflow. In some examples, the controller may also be connected to the battery, in addition to being connected to the charging electronics and the fan assembly. Further, in some examples, the wearable air purifier may further comprise a battery parameter sensor for measuring a parameter of the battery, wherein the controller is connected to the battery parameter sensor, and wherein the controller is configured to operate the fan assembly to generate airflow based on both the detected operation of the charging electronics and the measured parameter of the battery. Accordingly, in some examples the controller may be configured to avoid unnecessary power consumption by preventing unnecessary operation of the fan assembly based on the measured parameter of the battery, thereby also reducing unnecessary acoustic noise generation. In some examples, the controller may be configured to determine if the measured parameter of the battery meets a threshold. Further, in some examples the controller may be configured to subsequently operate the fan assembly to generate airflow in response to a determination that the measured parameter meets the threshold and based on the detected operation of the charging electronics. In some examples, the battery parameter sensor may comprise a temperature sensor operable to measure a temperature of the battery. Additionally or alternatively, the battery parameter sensor may comprise a resistance sensor operable to measure a resistance in the battery. In some examples, the controller may be configured to operate the fan assembly to generate airflow in the ducting arrangement in response to the detected operation of the charging electronics. Accordingly, in some examples the controller may be configured to operate the fan assembly to generate airflow in the ducting arrangement automatically when operation of the charging electronics is detected. Such an example may involve a simpler mode of operation, and may provide a failsafe to ensure that airflow is generated during a charging operation. In some examples, the ducting arrangement may comprise a main duct and a take-off duct. The main duct may direct airflow towards the wearer’s face and the charging electronics may be thermally coupled to airflow in the take-off duct. Accordingly, the airflow to which the charging electronics are thermally coupled can be directed and optimised for managing the temperature of the charging electronics without compromising performance of the main duct responsible for directing airflow to the wearer’s face in use. In some examples, the main duct may be defined at least in part by an air delivery mask connected to the headgear. An air delivery mask may facilitate improved delivery of airflow to the wearer’s face in use. In some examples, the ducting arrangement may comprise a valve operable to apportion the airflow received from the fan assembly between the main duct and the take-off duct based on the detected operation of the charging electronics. For examples, the fan assembly, valve and / or take-off duct may be configured to provide airflow to the take-off duct at a flow rate of between O.OlOL / s and 0.09L / s, preferably between 0.015L / s and 0.08L / s, such as 0.021L / s and / or 0.063L / s. In some examples, the valve may be an electromechanical flap valve. In some examples, the valve may comprise a smart material, such as a shape memory alloy or polymer. For example, the valve may change size and / or shape in response to temperature and / or electric current. In some examples the valve may comprise a bi-metallic strip. In some examples, the valve may be configured to direct at least 80%, preferably at least 90%, more preferably substantially all, of the airflow received from the fan assembly to the take-off duct in response to the detected operation of the charging electronics. Accordingly, during a battery charging operation, the valve may be operated to direct a majority, and preferably all, of the airflow generated by the fan assembly to the take-off duct and therefore to the charging electronics thermally coupled to the airflow in the take-off duct. In some examples, the wearable air purifier may further comprise a filter located upstream of the ducting arrangement such that the airflow received by the ducting arrangement is a filtered airflow. Further, in some examples the filter may be located upstream of the fan assembly. The filter may be responsible for filtering air that is subsequently directed towards the wearer’s face in use. A filter located upstream of the ducting arrangement such that the airflow in the ducting arrangement is a filtered airflow is particularly advantageous for examples wherein the charging electronics are directly thermally coupled to the airflow. This is because the airflow thermally coupled to the charging electronics in such an example is filtered, and therefore doesn’t contain contaminants that could damage the charging electronics, such as particulates, liquids, or salts such as NaCL for example which could deliquesce on the charging electronics and thereby increase the risk of a short circuit. In some examples the fan assembly may comprise an impeller coupled to an electric motor, and the controller may be configured to operate the electric motor at a substantially constant pre-defined speed based on the detected operation of the charging electronics. For example, the controller may be configured to operate the electric motor at a substantially constant predefined speed of between 1000 rpm and 4000 rpm based on the detected operation of the charging electronics. In some examples, the pre-defined speed may be substantially lower than a maximum operable speed of the electric motor (such as 10,000 rpm), i.e. a maximum speed of the electric motor when the wearable air purifier is in use and the charging electronics are not in operation. For example, the pre-defined speed may be less than 40%, preferably less than 30%, more preferably less than 20% of the maximum operable speed of the electric motor. In some examples, the fan assembly may comprise an impeller coupled to an electric motor, and the controller may be configured to operate the electric motor at a variable speed based on the detected operation of the charging electronics. Accordingly, the electronic motor may be operated at a speed that is determined to be sufficient by the controller in real-time, thereby improving the efficiency of the wearable air purifier and potentially reducing the time required for charging the battery. In some examples, the wearable air purifier may further comprise a charging electronics parameter sensor for measuring a parameter of the charging electronics, and the controller may be connected to the charging electronics parameter sensor, and the controller may be configured to operate the electric motor at a variable speed based on both the detected operation of the charging electronics and the measured parameter of the charging electronics. Accordingly, the speed of the electric motor may be determined, at least in part based on the measured parameter of the charging electronics such that the fan assembly is operated in accordance with the requirements of the charging electronics. For example, the charging electronics parameter sensor may be a temperature sensor, and the electric motor of the fan assembly may therefore be operated at a speed based at least in part on the temperature of the charging electronics. This may improve efficiency and reduce the power consumption of operating the fan assembly. In some examples, the wearable air purifier may further comprise a battery parameter sensor for measuring a parameter of the battery, and the controller may be connected to the battery parameter sensor, and the controller may be configured to operate the electric motor at a variable speed based on both the detected operation of the charging electronics and the measured parameter of the battery. For example, the battery parameter sensor may be a temperature sensor, and the electric motor of the fan assembly may therefore be operated at a speed based at least in part on the temperature of the battery. This may improve efficiency and reduce the power consumption of operating the fan assembly. In some examples, the wearable air purifier may further comprise an environment parameter sensor for measuring a parameter of the environment external to the wearable air purifier, and the controller may be connected to the environment parameter sensor, and the controller may be configured to operate the electric motor at a variable speed based on both the detected operation of the charging electronics and the measured parameter of the environment. For example, the environment parameter sensor may be a temperature sensor operable to measure an ambient temperature of air in the environment prior to entering the fan assembly and / or ducting arrangement. As such, the electric motor of the fan assembly may be operated at a speed based at least in part on the ambient temperature of the air in the environment. For example, if the air in the environment is relatively cold, a lower flow rate of air in the ducting arrangement may be sufficient for cooling the charging electronics, and the electric motor of the fan assembly may therefore be operated at a lower speed. This may improve efficiency and reduce the power consumption of operating the fan assembly. In some examples, the controller may be configured to detect cessation of operation of the charging electronics. Further, the controller may be configured to continue to operate the fan assembly to generate airflow in the ducting arrangement for a pre-defined time period after detecting cessation of operation of the charging electronics. For example, the controller may be configured to detect a fully-charged battery state, and the controller may be configured to continue to operate the fan assembly to generate airflow in the ducting arrangement for a pre-defined time period after detecting the fully-charged battery state. This may help to ensure that airflow continues to be provided after operation of the charging electronics ceases, thereby ensuring that any residual excess heat is removed from the charging electronics, reducing thermal cycling and associated degradation of the electronic components. BRIEF DESCRIPTION OF THE DRAWINGS Figure lisa schematic representation of a wearable air purifier; Figure 2 is an enlarged view of a portion of the wearable air purifier; and Figure 3 is a schematic diagram indicating an example of airflow and communication between components of the wearable air purifier. DETAILED DESCRIPTION Figure 1 is a schematic cross-sectional representation of a wearable air purifier 10. The wearable air purifier 10 comprises headgear 12 for wearing on a wearer’s head in use. As such, the wearable air purifier 10 may be supported on the head of the wearer by the headgear 12. The headgear 12 may comprise a band or strap configured to extend over or around the wearer’s head. The wearable air purifier 10 also includes a fan assembly 14 that is operable to generate an airflow, as shown more clearly in the enlarged cross-sectional view in Figure 2. For example, the fan assembly 14 may include an impeller 16 coupled to an electric motor 18, i.e. the impeller 16 may be driven by the electric motor 18. The wearable air purifier 10 includes a battery 20 to supply electrical power to the fan assembly 14, for example to drive the electric motor 18 of the fan assembly 14. A ducting arrangement 22 is also included in the wearable air purifier 10 for guiding the airflow from the fan assembly 14. The ducting arrangement 22 is configured to receive the airflow from the fan assembly 14 and direct the airflow towards the wearer’s face, in use. An air filter 24 may be located upstream of the ducting arrangement 22 such that the airflow received by the ducting arrangement 22 is a filtered airflow. It follows that the airflow directed towards the wearer’s face may therefore be a filtered airflow. In some examples the ducting arrangement 22 comprises a main duct 22a that directs airflow towards the wearer’s face. As shown in Figure 1, in some examples the main duct 22a may be defined at least in part by an air delivery mask 26 connected to the headgear 12 to target the airflow at the mouth and / or nose of the wearer. The air delivery mask 26 may be shaped in a curved configuration to optimise the delivery of airflow to the wearer’s face. In some examples the wearable air purifier 10 may comprise a headphone system comprising a pair of speaker assemblies 28 mounted on the headgear 12. Each speaker assembly may comprise one or more speakers, such as electroacoustic transducers that convert an electrical signal to a corresponding acoustic sound. Each speaker may be housed within an ear cup 30 configured for arrangement on or over the wearer’s ears. Further, one or more of the previously described features of the wearable air purifier 10, such as the fan assembly 14, the filter 24, the ducting arrangement 22, or the battery 20 may be at least party located in one or both of the ear cups, in some examples. As described by way of background, charge in the battery 20 is depleted by powering the wearable air purifier 10 in use, for example by operating the fan assembly 14. Accordingly, the wearable air purifier 10 comprises charging electronics 32 to supply electrical power to the battery 20 to charge the battery 20 and thereby facilitate continued use of the wearable air purifier 10. By way of example, the charging electronics 32 may include a power management unit and associated series components such as a connector (for example a USB C connector), a Positive Temperature Coefficient fuse (PTC), and an upstream protection device, among other possible components. The charging electronics 32 may be at least partially located in one or both of the ear cups in some examples. In some examples, operation of the charging electronics 32 to charge the battery 20 may cause a build-up of heat, for example due to resistance in the charging electronics 32. To ensure that the charging electronics 32 do not overheat and to reduce thermal cycling, the charging electronics 32 are thermally coupled to airflow in the ducting arrangement 22. As such, heat from the charging electronics 32 can be dissipated to the airflow in the ducting arrangement 22. In some examples, the ducting arrangement 22 may include a take-off duct 22b and the charging electronics 32 may be thermally coupled to airflow in the take-off duct 22b. The take-off duct 22b may be at least partially located in one or both of the ear cups, in some examples. With reference additionally to Figure 3, a controller 34 is included in the wearable air purifier 10 and connected to both the charging electronics 32 and the fan assembly 14. It will be appreciated that the controller 34 therefore communicates with both the charging electronics 32 and the fan assembly 14. An example of communication between the controller 34 and the various components of an example of the wearable air purifier 10 is indicated by the dashed arrows in the schematic diagram of Figure 3. The controller 34 is configured to detect operation of the charging electronics 32. Accordingly, the controller 34 may be configured to receive a signal from the charging electronics 32 which indicates that the charging electronics 32 are in operation, for example to charge the battery 20. The controller 34 is also configured to operate the fan assembly 14 to generate airflow in the ducting arrangement 22 based on the detected operation of the charging electronics 32. As such, the fan arrangement is operable to generate an airflow in the ducting arrangement 22 when instructed by the controller 34. This facilitates effective heat dissipation from the charging electronics 32 thermally coupled to the airflow, when required. An example of the movement of airflow through an example of the wearable air purifier 10 is indicated by the solid arrows in the schematic diagram of Figure 3. A valve (not shown) may be included in the ducting arrangement 22 in some examples. The valve may be operable to apportion the airflow received from the fan assembly 14 between the main duct 22a and the take-off duct 22b based on the detected operation of the charging electronics 32. As such the valve may be coupled to the controller 34. For example, when the charging electronics 32 are in operation, the valve may be configured to direct at least 80% of the airflow received from the fan assembly 14 to the take-off duct 22b in response to detected operation of the charging electronics 32. In some examples the valve may be operable to vary the proportion of airflow directed to the main duct 22a and to the take-off duct 22b based on control commands received from the controller 34. In some examples, the controller 34 may be configured to operate the fan assembly 14 to generate airflow in the ducting arrangement 22 in response to the detected operation of the charging electronics 32. In other words, the controller 34 may be configured to automatically initiate operation of the fan assembly 14 upon detection that the charging electronics 32 are in operation. Such a configuration may help to ensure that airflow is generated in the ducting arrangement 22 for the entire time period that the battery 20 is charged via the charging electronics 32. In other examples, operation of the fan assembly 14 to generate airflow in the ducting arrangement 22 may be based on one or more other factors in addition to operation of the charging electronics 32. For example, as shown in Figure 3, in some examples the wearable air purifier 10 may include a charging electronics parameter sensor 36 for measuring a parameter of the charging electronics 32. The charging electronics parameter sensor 36 may be a temperature sensor operable to measure a temperature of the charging electronics 32, in some examples. The controller 34 may be connected to the charging electronics parameter sensor 36, and may for example receive sensor data from the charging electronics parameter sensor 36. Accordingly, the controller 34 may be configured to operate the fan assembly 14 to generate airflow in the ducting arrangement 22 based on both the detected operation of the charging electronics 32 and the measured parameter of the charging electronics 32. Further, in some examples the controller 34 may be configured to determine if the measured parameter of the charging electronics 32 meets a threshold. In response to a determination that the measured parameter meets the threshold, the controller 34 may be configured to subsequently operate the fan assembly 14 to generate airflow in the ducting arrangement 22. Accordingly, operation of the fan assembly 14 may be based on detected operation of the charging electronics 32 and the threshold determination, such that the airflow is only generated when charging if the threshold is met. In some examples, the controller 34 may also be configured to operate the electric motor 18 at a variable speed based on both the detected operation of the charging electronics 32 and the measured parameter of the charging electronics 32. With brief reference again to Figure 1, in some examples the battery 20 may be thermally coupled to airflow generated by the fan assembly 14. For example, airflow may be directed towards the battery 20 by a vent or opening 38 in one or both of the ear cups, in some examples. In some examples where the battery 20 is thermally coupled to the generated airflow, the wearable air purifier 10 may also include a battery parameter sensor 40 for measuring a parameter of the battery 20. For example, the battery parameter sensor 40 may comprise a temperature sensor operable to measure a temperature of the battery 20. It follows that the controller 34 may be connected to the battery parameter sensor 40, and that the controller 34 may be configured to operate the fan assembly 14 to generate airflow based on both the detected operation of the charging electronics 32 and the measured parameter of the battery 20. As described previously with reference to the charging electronics parameter sensor 36, the controller 34 may be configured to determine if the measured parameter of the battery 20 meets a threshold. The controller 34 may be configured to subsequently operate the fan assembly 14 in response to a positive determination that the measured parameter meets the threshold, and based on the detected operation of the charging electronics 32. In some examples, the controller 34 may also be configured to operate the electric motor 18 at a variable speed based on both the detected operation of the charging electronics 32 and the measured parameter of the battery 20. Referring still to Figure 3, in some examples the wearable air purifier 10 may include an environment parameter sensor 42 for measuring a parameter of the environment external to the wearable air purifier 10. Such a parameter sensor may be a temperature sensor operable to measure the ambient temperature of the air before it is introduced to the fan assembly 14, in some examples. It follows that the controller 34 may be connected to the environment parameter sensor 42. In some examples, the controller 34 may therefore be configured to operate the electric motor 18 at a variable speed based on both the detected operation of the charging electronics 32 and the measured parameter of the environment. For example, if the ambient air temperature is relatively cold, the fan assembly 14 may be operated at a lower speed because a relatively lower flowrate of air is sufficient for dissipating heat from the charging electronics 32, in comparison to an example where the ambient air temperature is comparatively warmer. With reference to Figure 3, it will be appreciated that in some examples, the wearable air purifier 10 may comprise each of a charging electronics parameter sensor 36, a battery parameter sensor 40, and an environment parameter sensor 42, and operation of the fan assembly 14 may be based on a sensor data from each of the parameter sensors as described previously. However, it will be appreciated that in some examples, the wearable air purifier 10 may comprise any combination of parameter sensors, and the fan assembly 14 may be operated by the controller 34 based on the sensor data from any of one or more of the parameter sensors. As such, the fan assembly 14 may be operated at a variable speed by the controller 34 based on the sensor data from any of one or more of the parameter sensors, in some examples. In some other examples the controller 34 may be configured to operate the electric motor 18 at a variable speed based on the detected operation of the charging electronics 32, without necessarily requiring an input from one or more parameter sensors. Alternatively, the controller 34 may be configured to operate the electric motor 18 at a substantially constant pre-defined speed based on the detected operation of the charging electronics 32. Whilst not shown in the accompanying figures, in some examples the valve may be connected to the controller 34, and may therefore be configured to receive operating signals from the controller 34. As such, the controller 34 may be configured to operate the valve (not shown) to vary the flowrate and / or proportion of airflow in the take-off duct 22b based on sensor data from one or more parameter sensors. Finally, as previously described, the controller 34 is configured to detect operation of the charging electronics 32. As such, it will be appreciated that the controller 34 may also be configured to detect cessation of operation of the charging electronics 32. For example, the controller 34 may be configured to detect when the charging electronics 32 are disconnected from a power supply (not shown), or when the battery 20 reaches a fully charged state. In some examples the controller 34 may be configured to continue to operate the fan assembly 14 to generate airflow in the ducting arrangement 22 for a pre-defined time period after detecting the operation of the charging electronics 32 has ceased. This may help to ensure that heat is thoroughly dissipated from the charging electronics 32 to the airflow. It will be appreciated that the description provided herein serves to demonstrate possible examples of the present invention. Features described in relation to any of the examples herein may be readily combined with any other features described with reference to different examples without departing from the scope of the invention as defined in the appended claims.

Claims

1. A wearable air purifier (10), comprising:headgear (12) for wearing on a wearer’s head,a fan assembly (14) operable to generate an airflow,a ducting arrangement (22) configured to receive the airflow from the fan assembly (14) and direct the airflow towards the wearer’s face,a battery (20) to supply electrical power to the fan assembly (14),charging electronics (32) to supply electrical power to the battery (20) to charge the battery, wherein the charging electronics (32) are thermally coupled to airflow in the ducting arrangement (22), anda controller (34) connected to the charging electronics (32) and to the fan assembly (14),wherein the controller (34) is configured to detect operation of the charging electronics (32) and to operate the fan assembly (14) to generate airflow in the ducting arrangement (22) based on the detected operation of the charging electronics (32); and,wherein the ducting arrangement (22) comprises a main duct (22a) and a takeoff duct (22b), wherein the main duct (22a) directs airflow towards the wearer’s face and wherein the charging electronics (32) are thermally coupled to airflow in the take-off duct (22b).

2. The wearable air purifier (10) of Claim 1, further comprising a charging electronics parameter sensor (36) for measuring a parameter of the charging electronics (32), wherein the controller (34) is connected to the charging electronics parameter sensor (36), and wherein the controller (34) is configured to operate the fan assembly (14) to generate airflow in the ducting arrangement (22) based on both the detected operation of the charging electronics (32) and the measured parameter of the charging electronics (32).

3. The wearable air purifier (10) of Claim 2, wherein the controller (34) is configured to determine if the measured parameter of the charging electronics (32) meets a threshold and to subsequently operate the fan assembly (14) to generate airflow in the ductingarrangement (22) in response to a determination that the measured parameter meets the threshold and based on the detected operation of the charging electronics (32).

4. The wearable air purifier (10) of Claim 2 or Claim 3, wherein the charging electronics parameter sensor (36) comprises a temperature sensor operable to measure a temperature of the charging electronics (32).

5. The wearable air purifier (10) of any preceding claim, wherein the battery (20) is thermally coupled to airflow generated by the fan assembly (14).

6. The wearable air purifier (10) of Claim 5, further comprising a battery parameter sensor (40) for measuring a parameter of the battery (20), wherein the controller (34) is connected to the battery parameter sensor (40), and wherein the controller (34) is configured to operate the fan assembly (14) to generate airflow based on both the detected operation of the charging electronics (32) and the measured parameter of the battery (20).

7. The wearable air purifier (10) of Claim 6, wherein the controller (34) is configured to determine if the measured parameter of the battery (20) meets a threshold and to subsequently operate the fan assembly (14) to generate airflow in response to a determination that the measured parameter meets the threshold and based on the detected operation of the charging electronics (32).

8. The wearable air purifier (10) of Claim 6 or Claim 7, wherein the battery (20) parameter sensor (40) comprises a temperature sensor operable to measure a temperature of the battery (20).

9. The wearable air purifier (10) of Claim 1, wherein the controller (34) is configured to operate the fan assembly (14) to generate airflow in the ducting arrangement (22) in response to the detected operation of the charging electronics (32).

10. The wearable air purifier (10) of any preceding claim, wherein the main duct (22a) is defined at least in part by an air delivery mask (26) connected to the headgear (12).

11. The wearable air purifier (10) of any preceding claim, wherein the ducting arrangement (22) comprises a valve operable to apportion the airflow received from the fan assembly (14) between the main duct (22a) and the take-off duct (22b) based on the detected operation of the charging electronics (32).

12. The wearable air purifier (10) of Claim 11, wherein the valve is configured to direct at least 80%, preferably at least 90%, more preferably substantially all, of the airflow received from the fan assembly (14) to the take-off duct (22b) in response to the detected operation of the charging electronics (32).

13. The wearable air purifier (10) of any preceding claim, further comprising a filter located upstream of the ducting arrangement (22) such that the airflow received by the ducting arrangement (22) is a filtered airflow.

14. The wearable air purifier (10) of any preceding claim, wherein the fan assembly (14) comprises an impeller (16) coupled to an electric motor (18), and wherein the controller (34) is configured to operate the electric motor (18) at a substantially constant pre-defined speed based on the detected operation of the charging electronics (32).

15. The wearable air purifier (10) of any of Claims 1 to 13, wherein the fan assembly (14) comprises an impeller (16) coupled to an electric motor (18), and wherein the controller (34) is configured to operate the electric motor (18) at a variable speed based on the detected operation of the charging electronics (32).

16. The wearable air purifier (10) of Claim 15, further comprising a charging electronics parameter sensor (36) for measuring a parameter of the charging electronics (32), wherein the controller (34) is connected to the charging electronics (32) parameter sensor (36), and wherein the controller (34) is configured to operate the electric motor (18) at a variable speed based on both the detected operation of the charging electronics (32) and the measured parameter of the charging electronics (32).

17. The wearable air purifier (10) of Claim 15 or Claim 16, further comprising a battery parameter sensor (40) for measuring a parameter of the battery (20), wherein the controller (34) is connected to the battery parameter sensor (40), and wherein the controller (34) is configured to operate the electric motor (18) at a variable speed based on both the detected 5 operation of the charging electronics (32) and the measured parameter of the battery (20).

18. The wearable air purifier (10) of any of Claims 15 to 17, further comprising an environment parameter sensor (42) for measuring a parameter of the environment external to the wearable air purifier (10), wherein the controller (34) is connected to the environment 10 parameter sensor (42), and wherein the controller (34) is configured to operate the electric motor (18) at a variable speed based on both the detected operation of the charging electronics (32) and the measured parameter of the environment.

19. The wearable air purifier (10) of any preceding claim, wherein the controller (34) is 15 configured to detect cessation of operation of the charging electronics (32) and to continue to operate the fan assembly (14) to generate airflow in the ducting arrangement (22) for a pre-defined time period after detecting cessation of operation of the charging electronics (32).

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