Patent Description:
Cabin air systems in example vehicles and aircraft are designed to provide a comfortable cabin environment. In some example aircraft, the aircraft cabin is pressurized to enable passengers and crew to breathe normally. Air enters a passenger area from overhead distribution outlets that run a length of the aircraft cabin and generate airflow within the cabin. Air supplied to the cabin contains a mixture of recirculated air from within the cabin and air from outside the aircraft. Air is exhausted through air returns located along the length of the cabin, such that air is supplied to and exhausted from the passenger area on a continuous basis.

Other vehicles, such as trains and buses, have air circulation systems that circulate air for purposes of passenger comfort. In many vehicles, there is a centralized air unit that may circulate both external air introduced into the vehicle as well as air re-circulated inside the vehicle, where contaminants and airborne particulates may be present in the air. Airborne particulates include a complex mixture of organic and inorganic substances, including bacteria, germs, a variety of airborne viruses, and other substances that are small enough to become suspended in the air, where exposure of passengers to airborne particulates poses risks of infection and contagion.

Those skilled in the art will readily appreciate that all of the above-mentioned issues may represent significant considerations with respect to the overall operations of an airline or other vehicle operator. Thus, there exists a continuing need for an improved, cost-effective approach for circulating air within a vehicle.

<CIT>, in accordance with a translation of its abstract, states a sleeve type photocatalysis air cleaning device is based on dispersion optical fibers. The sleeve type photocatalysis air cleaning device comprises a filtering unit, an optical fiber unit and a catalyst unit, wherein the filtering unit is a cylinder-shaped filtering unit; the radial cross section of the filtering unit is annular, and upper and lower ends of the filtering unit are respectively connected with a top end cover and a bottom end cover; the catalyst unit is a cylinder-shaped catalyst unit, the radial cross section of the catalyst unit is annular, the height of the catalyst unit is the same as that of the filtering unit, the diameter of the catalyst unit is smaller than that of the filtering unit, and the catalyst unit and the filtering unit can form a concentric sleeve type structure; the center of the top end cover is provided with an air outlet, and the top end cover is provided with a top end installing hole; bottom installing holes are uniformly formed in the bottom end cover, the optical fiber unit selects the fibrous optical fibers, one end of the optical fiber unit is connected with the top end installing hole, and the other end of the optical fiber unit is connected with the bottom installing holes. The sleeve type photocatalysis air cleaning device has the advantages that <NUM>-degree lateral air incoming is adopted, secondary pollution caused by a by-product of a light-catalyzed reaction is effectively reduced, the ultraviolet light use ratio is improved, meanwhile, the air purification efficiency is improved, and the sleeve type photocatalysis air cleaning device is suitable for sealing, flammable and combustible environment such as airplanes, subways and factories.

<CIT>, in accordance with its abstract, states a method for air conditioning of an aircraft includes the steps of: (A) obtaining a fresh air for ventilation; (B) exhausting an air from a cabin; (C) obtaining a purified air for recirculation, from a part of the air exhausted in the step (B); (D) obtaining an air for ventilation; (E) supplying the air for ventilation to the cabin; and (F) irradiating an ultraviolet ray emitted from a UV-LED to the fresh air for ventilation, an air for recirculation, the purified air for recirculation, and/or the air for ventilation.

This section is intended to introduce the reader to various features of art that may be related to various features of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various features of the present disclosure.

There is described herein an apparatus for irradiating air in an air circulation system of a vehicle, the apparatus comprising: a filter unit for coupling to a recirculating air conduit of the air circulation system, the filter unit having an inlet end; a filter disposed in the inlet end of the filter unit, comprising an outer High Efficiency Particulate Air (HEPA) media filter, and an inner activated carbon filter defining an interior volume of the filter; a plurality of ultraviolet light transmissive strands that each have distal ends disposed in a spaced apart manner in an interface region between the outer HEPA media filter and the inner activated carbon filter, and proximal ends configured for connection to an ultraviolet light emitting source such that ultraviolet light is transmitted by the plurality of ultraviolet light transmissive strands into the interface region between the outer HEPA media filter and the inner activated carbon filter; and an end plate disposed over an open end of the filter, having an aperture though which the plurality of ultraviolet light transmissive strands extend. The ultraviolet light transmissive strands are configured to receive ultraviolet light emitted by the ultraviolet light emitting source that is substantially at between <NUM> and <NUM>, and to transmit the ultraviolet light into the air passing through the interface region between the outer HEPA media filter and the inner activated carbon filter and into the air circulation system. Each of the distal ends of the plurality of ultraviolet light transmissive strands are of varying lengths, such that the distal ends are positioned at different locations within the interface region between the outer HEPA media filter and the inner activated carbon filter.

According to various examples, an apparatus for irradiating air within an air circulation system of a vehicle includes a filter unit to couple to a recirculating air conduit that is coupled to an air circulation system. A filter is disposed in an inlet end of the filter unit, and includes an outer High Efficiency Particulate Air (HEPA) media filter, and an inner activated carbon filter media defining an interior volume. The apparatus further includes a plurality of ultraviolet light transmissive strands that each have distal ends disposed in a spaced apart manner in an interface region between the outer HEPA media filter and the inner activated carbon filter, and proximal ends connectable to an ultraviolet light emitting source such that ultraviolet light is transmitted by the transmissive strands into an interface region between the outer HEPA media filter and the inner activated carbon filter. The ultraviolet light transmissive strands can receive emitted ultraviolet light that is between <NUM> and <NUM> or substantially between <NUM> and <NUM> for irradiating air passing through the filter.

According to other examples, a method for irradiating air in an air circulation system of a vehicle includes coupling a filter unit to a recirculating air conduit that is connected to an air circulation system. The method includes positioning the distal ends of a plurality of ultraviolet light transmissive strands in a spaced apart manner along an outer surface of an activated carbon filter, and positioning the activated carbon filter within a High Efficiency Particulate Air (HEPA) media filter, such that the distal ends of a plurality of ultraviolet light transmissive strands are disposed along an interface region between the outer HEPA media filter and the inner activated carbon filter. The method further includes securing the filter including the ultraviolet light transmissive strands relative to the filter unit, and connecting a proximal end of each of the plurality of ultraviolet light transmissive strands to an ultraviolet light emitting source such that ultraviolet light emitted by the source is transmitted by the transmissive strands into an interface region between the outer HEPA media filter and the inner activated carbon filter. The method further includes activating the ultraviolet light emitting source, to cause the ultraviolet light source to emit ultraviolet radiation at between <NUM> and <NUM> or substantially at between <NUM> and <NUM> that is transmitted by the transmissive strands for irradiating air passing through the filter into the air circulation system.

Further areas of applicability will become apparent from the description herein. The description and specific examples in the summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

Various refinements exist of the features noted above in relation to the various examples of the present disclosure. Further features may also be incorporated in these various examples as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated examples may be incorporated into any of the above-described examples of the present disclosure alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain examples and contexts of the present disclosure without limitation to the claimed subject matter.

The drawings described herein are for illustrative purposes only of selected examples and not all possible examples, and are not intended to limit the scope of the present disclosure.

Examples will now be described more fully with reference to the accompanying drawings. Examples are described of an apparatus for irradiation treatment of air within an air circulation system of a vehicle. The features, functions, and advantages discussed in the preceding section can be achieved independently in various examples or may be combined in yet other examples. Further examples of the present disclosure can be seen with reference to the drawings and the following description.

In some examples, an apparatus for irradiation treatment of air within an air circulation system of a vehicle includes a filter unit configured to couple to a recirculating-air conduit coupled to an air circulation system, the filter unit having an inlet end. A filter is disposed in the inlet end of the filter unit, and includes an outer High Efficiency Particulate Air (HEPA) media filter, and an inner activated carbon filter media defining an interior volume. The apparatus further includes a plurality of ultraviolet light transmissive strands that each have distal ends disposed in a spaced apart manner in an interface region between the outer HEPA media filter and the inner activated carbon filter, and proximal ends connectable to an ultraviolet light emitting source such that ultraviolet light is transmitted by the transmissive strands into an interface region between the outer HEPA media filter and the inner activated carbon filter. The ultraviolet light transmissive strands are configured to receive emitted ultraviolet light that is between <NUM> and <NUM> or substantially between <NUM> and <NUM> for irradiating air passing through the filter.

Referring to <FIG>, a vehicle including an aircraft <NUM> has a passenger air distribution system that receives air from an air circulation system. The air distribution system supplies air that enters a passenger area from overhead distribution outlets that run a length of the aircraft cabin and generate airflow in the cabin. Air supplied to the cabin contains a mixture of recirculated air from in the cabin and air from outside the aircraft. Air is drawn through air returns located near the floor along the length of the cabin, such that air is supplied to and removed from the cabin passenger area on a continuous basis.

<FIG> is an illustration of an air circulation system <NUM> of a vehicle - such as the aircraft <NUM> shown in <FIG> - including an example of an apparatus for irradiating air flow to the air circulation system <NUM>. The air circulation system <NUM> includes a recirculating-air conduit <NUM> (in which a recirculating fan may be disposed) that is connected to a mix manifold <NUM> of the air circulation system <NUM>, where the mix manifold <NUM> receives supply of outside air from outside the aircraft <NUM> from an Environmental Control System (ECS) and also receives recirculated air via filtered inputs. The mix manifold <NUM> also supplies two air distribution lines to supply circulated air to passengers in the cabin.

<FIG>, depicts an example of an apparatus <NUM> for irradiation treatment of air within an air circulation system <NUM> such as that shown in <FIG>, for a vehicle such as aircraft <NUM> in <FIG>. The apparatus <NUM> includes a filter unit <NUM> configured to couple to a recirculating air conduit <NUM> connected to the mix manifold <NUM> of the air circulation system <NUM>, where the filter unit <NUM> has an inlet end <NUM>. A filter <NUM> is disposed in the inlet end <NUM> of the filter unit <NUM>, and includes an outer High Efficiency Particulate Air (HEPA) media filter 120A and an inner activated carbon filter 120B (not shown in <FIG>). The apparatus <NUM> further includes a plurality of ultraviolet light transmissive strands that each have distal ends disposed in a spaced apart manner in an interface region between the outer HEPA media filter 120A and the inner activated carbon filter 120B, and proximal ends connectable to an ultraviolet light emitting source such that ultraviolet light is transmitted by the transmissive strands into an interface region between the outer HEPA media filter 120A and the inner activated carbon filter 120B. The apparatus <NUM> further comprises an end plate <NUM>, configured to be mounted with the end plate <NUM> against an open end of the filter <NUM>, wherein the ultraviolet light transmissive strands are configured to transmit ultraviolet radiation at between <NUM> and <NUM> or substantially at between <NUM> and <NUM> for irradiating air passing through the filter <NUM> into the air circulation system <NUM>.

In an example, the apparatus <NUM> includes the filter unit <NUM> that is coupled to the recirculating air conduit <NUM>, which is connected to the mix manifold <NUM> of the air circulation system <NUM>. The filter <NUM> is disposed at the inlet end <NUM> of the filter unit <NUM>, where the filter <NUM> may have a circular, rectangular, or triangular shape and an outer surface through which air is drawn, where the filter shape defines an interior volume through which air passes through the media of the filter <NUM> to the interior volume. The outer High Efficiency Particulate Air (HEPA) filter 120A may include an outer annular portion of the filter <NUM> forming a pleated cartridge made with a High Efficiency Particulate Air (HEPA) media, and the inner activated carbon filter 120B may include an inner annular portion of the filter <NUM> that includes activated carbon. The filter <NUM> may have a cylindrical shape, and may include the outer High Efficiency Particulate Air (HEPA) media 120A and the inner activated carbon filter media 120B defining an interior volume of the filter <NUM>. More specifically, in some examples, the outer pleated High Efficiency Particulate Air (HEPA) media 120A includes an outer annular portion of the filter <NUM> forming a pleated cartridge made with a High Efficiency Particulate Air (HEPA) media, and the inner activated carbon filter media 120B includes an inner annular portion of the filter <NUM> that includes activated carbon.

In an example shown in <FIG>, the apparatus <NUM> includes a plurality of ultraviolet light transmissive strands <NUM> that each have distal ends 140A disposed in a spaced apart manner in an interface region <NUM> (see <FIG>) between the outer HEPA media filter 120A and the inner activated carbon filter 120B, and proximal ends connectable to an ultraviolet light emitting source such that ultraviolet light is transmitted by the transmissive strands into the interface region <NUM> between the outer HEPA media filter 120A and the inner activated carbon filter 120B. The ultraviolet light transmissive strands <NUM> may be overlaid on or disposed on an outer surface of the inner activated carbon filter 120B, such that the distal ends 140A of the plurality of ultraviolet light transmissive strands <NUM> are positioned in a spaced apart manner along an outer surface of the activated carbon filter 120B, as shown in <FIG>. The transmissive strands <NUM> overlaid on the activated carbon filter 120B are then positioned within the outer High Efficiency Particulate Air (HEPA) media filter 120A, as shown in <FIG>, such that the distal ends 140A of the plurality of ultraviolet light transmissive strands <NUM> are disposed along the interface region <NUM> between the outer HEPA media filter 120A and the inner activated carbon filter 120B. In some examples, the distal ends 140A of the plurality of ultraviolet light transmissive strands <NUM> are removably disposed between the outer HEPA media filter 120A and the inner activated carbon filter 120B, such that they can be removed and replaced. The proximal end of each of the plurality of ultraviolet light transmissive strands <NUM> are connected to an ultraviolet light emitting source, such that ultraviolet light emitted by the source is transmitted by the transmissive strands <NUM> into the interface region <NUM> between the outer HEPA media filter 120A and the inner activated carbon filter 120B. The filter <NUM> including the ultraviolet light transmissive strands <NUM> is positioned relative to the filter unit <NUM>, and the end plate <NUM> is positioned against the open end of the filter <NUM>.

The distal ends 140A of the plurality of ultraviolet light transmissive strands <NUM> are each of varying lengths, such that the distal ends 140A are positioned at different locations within the interface region <NUM> between the outer HEPA media filter 120A and the inner activated carbon filter 120B. The distal ends 140A of the plurality of ultraviolet light transmissive strands <NUM> are positioned at various locations within the interface region <NUM> between the outer HEPA media filter 120A and the inner activated carbon filter 120B, such that ultraviolet light is scattered throughout the interface region <NUM>. In some examples, the outer HEPA media filter 120A is made of woven fiberglass, where the transmitted ultraviolet light emitted at the interface region <NUM> is reflected and scattered by the woven fiberglass to disperse UV light and irradiate the interface region <NUM> between the outer HEPA media filter 120A and the inner activated carbon filter 120B. In some examples, the proximal ends of the plurality of ultraviolet light transmissive strands <NUM> are joined into a single strand that is positioned relative to an ultraviolet light source, and may be connected to a connector proximate to the end plate <NUM>. In some examples, the ultraviolet light source emits ultraviolet radiation at between <NUM> and <NUM> at a power flux or irradiation of at least <NUM>,<NUM> microwatts per square centimeter, such that the intensity of ultraviolet radiation is sufficient to kill and/or degrade microorganisms, viruses, bacteria, germs, mold, and other contaminants in the air flowing through the filter. In some examples, the plurality of ultraviolet light transmissive strands <NUM> include optical fibers suitable for fiber-optic transmission of ultraviolet light. One such optical fiber is Molex® Silica Optical Fiber sold by Laser Components. In some examples, the apparatus <NUM> further includes, as an ultraviolet light source, an ultraviolet light emitting diode (LED) positioned relative to the proximal ends of the plurality of ultraviolet light transmissive strands <NUM> including optical fibers, where the ultraviolet LED emits ultraviolet light into the proximal ends of the ultraviolet light transmissive strands <NUM>, which transmit the ultraviolet light to the interface region <NUM> to irradiate the air passing through the outer HEPA media filter 120A, the interface region <NUM>, and the inner activated carbon filter 120B into the air circulation system <NUM>. An example may be an ultraviolet LED part number VPS134 sold by Boston Scientific. In some examples, the ultraviolet light source is configured to emit a distribution of frequencies of ultraviolet radiation ranging at between <NUM> and <NUM> or substantially at between <NUM> and <NUM>, where the range is sufficient to result in generation of a minimal amount of ozone. An ultraviolet light source having a wavelength below <NUM> can generate ozone, while an ultraviolet light source having an emission frequency in the range of <NUM> to <NUM> (or about <NUM> to <NUM>) can potentially destroy ozone or reduce the level of ozone, where the emission of a range of ultraviolet radiation up to a frequency of <NUM> potentially reduces or limits the extent of ozone generated by emitted UV radiation at lower frequencies, such that the distribution of frequencies in the range of between <NUM> and <NUM> results in generation of a minimal amount of ozone within the filter <NUM>. The filter <NUM> including the ultraviolet light transmissive strands <NUM> is positioned relative to the filter unit <NUM>, and an end plate <NUM> is positioned against the open end of the filter <NUM>. The end plate <NUM> shown in <FIG> is, in some examples, configured to be mounted by attachment via rivets, adhesive, or bonding to the end of the filter <NUM>.

Referring to <FIG>, another example is shown of a filter (e.g., the filter <NUM>) including ultraviolet light transmissive strands <NUM>, which may be included in the apparatus <NUM> for irradiating air in an air circulation system (e.g., the air circulation system <NUM>). The filter includes a filter unit <NUM> (or filter housing), a plurality of ultraviolet light transmissive strands <NUM>, a HEPA filter 120A, and an activated carbon filter 120B. As shown in <FIG>, the distal ends 140A of the plurality of ultraviolet light transmissive strands <NUM> are positioned within an interface region <NUM> between the HEPA filter 120A and an activated carbon filter 120B such that the plurality of ultraviolet light transmissive strands <NUM> are disposed between the HEPA filter 120A and the activated carbon filter 120B. The proximal ends of the plurality of ultraviolet light transmissive strands <NUM> pass through a sealed connection in the filter unit <NUM>, where an ultraviolet light source may be positioned relative to (or connected to) the plurality of ultraviolet light transmissive strands <NUM> such that ultraviolet light emitted by the source is transmitted by the plurality of ultraviolet light transmissive strands <NUM>.

Additionally, the apparatus <NUM> may be configured to include a controller (not shown) that monitors an air flow sensor, mass flow sensor, or air particulate sensor disposed within the cabin of the aircraft (e.g., aircraft <NUM>, shown in <FIG>), to determine if the amount of recirculated irradiated air flow through the aircraft cabin is indicative of a minimum level for removing airborne particulates and contaminates, and thereafter discontinuing supply of power to the ultraviolet light source positioned relative to (or connected to) the plurality of ultraviolet light transmissive strands <NUM>. Similarly, the controller can monitor the sensor to determine if a measurement is indicative of the presence of more than an acceptable threshold of ozone or contaminant particulates are present in the cabin air, and thereafter deactivating the ultraviolet light emitter to discontinue ultraviolet light irradiation. Additionally, the controller may monitor the sensor to determine if the amount of recirculated irradiated air flow through the aircraft cabin is indicative of an insufficient level for removing airborne particulates and contaminates, and thereafter initiate the supply of power to the ultraviolet light to emit ultraviolet radiation at between <NUM> and <NUM> to irradiate the air flow through the filter <NUM> into the air circulation system <NUM>.

According to other examples, a method for irradiating air within an air circulation system of a vehicle includes coupling a filter unit to a recirculating-air conduit that is connected to a manifold of an air circulation system, the filter unit having an inlet end. The method further includes positioning the distal ends of a plurality of ultraviolet light transmissive strands in a spaced apart manner along an outer surface of an activated carbon filter, and positioning the activated carbon filter within a High Efficiency Particulate Air (HEPA) media filter, such that the distal ends of a plurality of ultraviolet light transmissive strands are disposed along an interface region between the outer HEPA media filter and the inner activated carbon filter. The method further includes securing the filter including the ultraviolet light transmissive strands relative to the filter unit, and connecting a proximal end of each of the plurality of ultraviolet light transmissive strands to an ultraviolet light emitting source such that ultraviolet light emitted by the source is transmitted by the transmissive strands into an interface region between the outer HEPA media filter and the inner activated carbon filter. The method further includes activating the ultraviolet light emitting source, to cause the ultraviolet light source to emit ultraviolet radiation at between <NUM> and <NUM> or substantially at between <NUM> and <NUM> that is transmitted by the transmissive strands for irradiating air passing through the filter into the air circulation system.

As illustrated in <FIG>, an example of a method is provided for irradiating air within an air circulation system of a vehicle. The method includes at step <NUM> coupling a filter unit to a recirculating-air conduit that is connected to a manifold of an air circulation system, the filter unit having an inlet end. The method includes, at step <NUM>, positioning the distal ends of a plurality of ultraviolet light transmissive strands in a spaced apart manner along an outer surface of an activated carbon filter. The method further includes, at step <NUM>, positioning the activated carbon filter within a High Efficiency Particulate Air (HEPA) media filter, such that the distal ends of a plurality of ultraviolet light transmissive strands are disposed along an interface region between the outer HEPA media filter and the inner activated carbon filter. At step <NUM>, the method includes securing the filter including the ultraviolet light transmissive strands relative to the filter unit, and an end plate positioned against an open end of the filter. The method may optionally include the step <NUM> of providing an ultraviolet light source that emits ultraviolet radiation at between <NUM> and <NUM> and a predetermined power level such that an intensity of the ultraviolet radiation is sufficient to kill and/or degrade viruses, bacteria, and other airborne microorganisms. The method further includes, at step <NUM>, connecting a proximal end of each of the plurality of ultraviolet light transmissive strands to an ultraviolet light emitting source such that activation of the source causes ultraviolet light emitted by the source to be transmitted by the transmissive strands into an interface region between the outer HEPA media filter and the inner activated carbon filter, for irradiating air flow passing through the filter into an air circulation system. The method further includes, at step <NUM>, activating the ultraviolet light emitting source, to cause the ultraviolet light source to emit ultraviolet radiation at between <NUM> and <NUM> or substantially at between <NUM> and <NUM> that is transmitted by the transmissive strands for irradiating air passing through the filter into the air circulation system. The method may optionally include the step <NUM> of activating the ultraviolet light source to emit ultraviolet radiation at a predetermined power level for a predetermined period of time, such that a sufficient amount of irradiate recirculating air flows through the air circulation system and aircraft cabin before further flight operation of the aircraft.

The examples fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of examples of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that examples may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some examples, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example examples only and is not intended to be limiting. It is also to be understood that additional or alternative steps may be employed, provided they fall within the scope of the appended claims.

Claim 1:
An apparatus (<NUM>) for irradiating air in an air circulation system (<NUM>) of a vehicle, the apparatus (<NUM>) comprising:
a filter unit (<NUM>) for coupling to a recirculating air conduit (<NUM>) of the air circulation system (<NUM>), the filter unit (<NUM>) having an inlet end (<NUM>);
a filter (<NUM>) disposed in the inlet end (<NUM>) of the filter unit (<NUM>), comprising an outer High Efficiency Particulate Air (HEPA) media filter (120A), and an inner activated carbon filter (120B) defining an interior volume of the filter (<NUM>);
a plurality of ultraviolet light transmissive strands (<NUM>) that each have distal ends (140A) disposed in a spaced apart manner in an interface region (<NUM>) between the outer HEPA media filter (120A) and the inner activated carbon filter (120B), and proximal ends configured for connection to an ultraviolet light emitting source such that ultraviolet light is transmitted by the plurality of ultraviolet light transmissive strands (<NUM>) into the interface region (<NUM>) between the outer HEPA media filter (120A) and the inner activated carbon filter (120B); and
an end plate (<NUM>) disposed over an open end of the filter (<NUM>), having an aperture though which the plurality of ultraviolet light transmissive strands (<NUM>) extend; and wherein
the ultraviolet light transmissive strands (<NUM>) are configured to receive ultraviolet light emitted by the ultraviolet light emitting source that is substantially between <NUM> and <NUM>, and to transmit the ultraviolet light into the air passing through the interface region (<NUM>) between the outer HEPA media filter (120A) and the inner activated carbon filter (120B) and into the air circulation system (<NUM>); and
each of the distal ends (140A) of the plurality of ultraviolet light transmissive strands (<NUM>) are of varying lengths, such that the distal ends (140A) are positioned at different locations within the interface region (<NUM>) between the outer HEPA media filter (120A) and the inner activated carbon filter (120B).