GB2601288A

GB2601288A - Air cleaning system and method

Info

Publication number: GB2601288A
Application number: GB2014112.3A
Authority: GB
Inventors: Said Raish Armando
Original assignee: City Air Technologies Ltd
Current assignee: City Air Technologies Ltd
Priority date: 2020-09-08
Filing date: 2020-09-08
Publication date: 2022-06-01
Anticipated expiration: 2040-09-08
Also published as: GB202014112D0; WO2022053772A1; GB2601288B

Abstract

An air cleaning system 1 comprises one or more planter units 5 each defining therein at least a plant chamber 6 containing a growth substrate 40 and plant(s) 45. An air flow generator 3 (fan) is in fluid communication with an air intake apparatus 2 which is in fluid communication with the interior volumes of the or each plant chamber and draws air into the system and expels air through an outlet 4. A respective air washing chamber 10 is located upstream of each plant chamber, with each including at least one ingress aperture 11 for air ingress from an environment and comprises therein one or more panels of wicking material 13 in contact with a water reservoir 12. The panel(s)s is/are configured such that air flow passes across and/or therethrough. Air is drawn into the air cleaning system by the air flow generator and passes first through the air washing chamber and second through the plant chamber such that air expelled through the outlet is cleaned as a result of both interaction with the water 30 carried by the panel(s) and by the moistened air passing through the growth substrate material located in the plant chamber.

Description

AIR CLEANING SYSTEM AND METHOD

This invention relates to systems and methods for cleaning air, utilising plants and the microbes which co-exist in the plant ecosystem to remove toxins and particulates from an air flow. The disclosed systems and methods are particularly well suited to incorporation into structures such as (internal or external) "living" or "green" walls, or items of furniture, but can take the form of standalone planters.

Phytoremediafion is a biological process carried out by plants and their associated micro-organisms in which environmental toxins are immobilised and removed, resulting in a decrease in the concentration of such toxins in the plants' environment. For example, toxins including volatile organic contaminants (VOCs) can be broken down by plant microbes and nitrogen dioxide (NO2) captured or dissolved thereby. Particulates such as pollen in the air can also be trapped in the growth substrate (e.g. soil) and/or suspended in water droplets found therein. The use of phytoremediation to improve air quality has been discussed and exemplary apparatus therefor described in US-A-2012/0052480, CA-A-2388583, WO-A-2014/123722 and EP-A-2734034, for instance. This approach to air cleaning has significant advantages over alternatives which rely on cartridges or replaceable filters since these must be regularly exchanged to maintain performance, and the resulting waste is hazardous and bad for the environment. By using the natural air cleaning cycles of plants and microbes to replace filters, a person can gain exposure to the many wellbeing and aesthetic benefits that plants provide, whilst reliably activating and utilising their existing plants to improve air quality.

However, the known systems and methods leave significant room for improvement. In particular, it would be desirable to increase the efficiency with which the system is able to clean air (i.e. to remove a greater proportion of toxins per unit of air, and/or to process more air per unit time). It would also be desirable to provide a system with significant design freedom which allows for flexibility in terms of how the system is configured -for instance horizontally, vertically or otherwise.

In accordance with the present invention, an air cleaning system is provided, comprising: one or more planter units, each planter unit defining therewithin at least a plant chamber adapted to contain a growth substrate and plant(s) in use; an air intake apparatus, fluidicly connected with the interior volumes of the or each plant chamber; an air flow generator, fluidicly connected to the air intake apparatus and configured to draw air in to the air cleaning system, and to expel the air through an outlet; characterised in that a respective air washing chamber is provided upstream of each plant chamber and fluidicly connected therewith, each air washing chamber including at least one ingress aperture for air ingress from the environment and comprising therein one or more panels of wicking material in contact with a water reservoir such that the one or more panels of wicking material carry water in use, the one or more panels being configured such that the air flow passes across and/or through the one or more panels; whereby, in use, air drawn into the air cleaning system by the air flow generator passes first through an air washing chamber and second through a plant chamber, such that the air expelled through the outlet is cleaned as a result of both interaction with the water carried by the panel(s) of wicking material and by the moistened air subsequently passing through a growth substrate material located in the plant chamber in use.

The invention further provides an air cleaning method, comprising: providing one or more planter units, each planter unit defining therewithin at least a plant chamber having a growth substrate and plant(s) rooted therein; providing an air intake apparatus, fluidicly connected with the interior volumes of the or each plant chamber; providing a respective air washing chamber upstream of each plant chamber and fluidicly connected therewith, each air washing chamber including at least one ingress aperture for air ingress from the environment and comprising therein one or more panels of wicking material in contact with a water reservoir containing water such that the one or more panels of wicking material carry water, and using an air flow generator, fluidicly connected to the air intake apparatus, to draw air in to the air cleaning system, and to expel the air through an outlet; whereby air is drawn into the air cleaning system by the air flow generator and passes first through an air washing chamber across and/or through the one or more panels, and second through a plant chamber, such that the air expelled through the outlet is cleaned as a result of both interaction with the water carried by the panel(s) of wicking material and by the moistened air subsequently passing through the growth substrate material located in the plant.

Since the microbes primarily responsible for phytoremediation are concentrated at the roots of the plants, it is critical to ensure the air is brought into contact with the root zone and not merely into the vicinity of the leaves or flowers. By providing an arrangement, as set out above, in which air is drawn from the environment first through an air washing chamber and then through a plant chamber (where it will interact with the growing medium and root system of the plants in use, to allow phytoremediation to occur), the efficiency of the phytoremediation process which takes place is increased in two ways. First, since the air is "pulled" through the plant chamber by the air flow generator (rather than moving in the opposite direction), the air flow rate can be made higher since it acts to retain the plant(s) and growth substrate within the plant chamber rather than applying an outward force. The higher the air flow rate, the more units of air can be treated per unit time.

Secondly, the provision of an air washing chamber upstream of the plant chamber increases the interaction between the air and the microbes and therefore more toxins are removed per unit of air treated than was previously the case. This is because the incoming air is humidified (i.e. the air picks up moisture) by its interaction with the wet surfaces of the wicking material panel(s) in the air washing chamber. The pre-moistening of the air immediately starts to break down some of the toxins in the air (particularly NO2) before they enter the plant root zone. As the air moves through the growth substrate, the molecules become suspended and trapped applying the microbes to reach them. The partial dilution of the toxins by the pre-moistening allows the microbes to better adhere to and break down the toxins in the air molecules as they pass through the plant chamber. This increases the absorption rate and the conversion of toxins to less harmful compounds.

In combination, these two effects significantly increase the efficiency of the phytoremediation process. In addition, the air flow is also cleaned by its interaction with the water in the air washing chamber, which suspends particulate materials such as dust or pollen, and dissolves other substances such as NO2. This further improves the overall effectiveness of the system and method. Furthermore, by locating the air washing chamber upstream of the plant chamber, any unpleasant odours (which might arise as a result of the water located in the air washing chamber) are themselves treated and removed from the air flow as it passes through the plant chamber.

The air washing chamber(s) could be provided separately from the plant chambers, connected thereto by suitable pipework for instance. However, in preferred embodiments, the or each air washing chamber is defined in the respective planter unit. This arrangement allows for straightforward and quick assembly of the system and also a significant degree of design freedom, since each plant chamber has its respective air washing chamber affixed thereto.

Advantageously, in each planter unit, the air washing chamber and the plant chamber are divided by an air-permeable wall, the air-permeable wall preferably being formed of a material which is hydrophobic. For example, the wall could be formed of a perforated plate with a filter fabric liner (to prevent clogging), or a rigid drainage board sandwiched between two layers of filter fabric. Whilst in some cases the filter fabric can act as further panel of wicking material (if placed in contact with the water reservoir), it is preferably formed of a hydrophobic (water-repelling) material so as not to increase resistance to the airflow through the system.

In some preferred implementations, in each planter unit, the air washing chamber is located at a first end of the planter unit, and the air intake apparatus is connected to the plant chamber at a second, opposite end of the planter unit. This is advantageous since it allows for the longest pathway of the air flow through the plant chamber (and hence growth substrate), resulting in more interaction with the microbes. However in other preferred embodiments, in each planter unit, the air washing chamber is located on at least two, preferably all, sides of the plant chamber This can be desirable in order to provide the air washing chamber with an increased open surface area which is accommodated without substantially changing the size or shape of the planter unit.

Whilst arranging for any proportion of the air flow to enter the system through the air washing chamber will achieve some improvement in cleaning efficiency, it is desirable to configure the system so that more air (preferably substantially all of the air) enters the system through the air washing chamber than through any open surface of the plant chamber. This will maximise the improvement in cleaning efficiency. The open surface area of the plant chamber will always present a resistance factor due the growth substrate density which in turn allows the air to take the path of least resistance. The ingress aperture(s) in the air washing chamber are, on the other hand, open and therefore present significantly less resistance. Nonetheless, preferably, any open surface area of the or each plant chamber in communication with the environment is configured to be less than the open surface area of the at least one ingress aperture of the respective air washing chamber This has the result that the open surface of the plant chamber will intrinsically offer more resistance to air flow than does the ingress aperture(s) of the air washing chamber so that more air enters the system through the air washing chamber than through the open surface of the plant chamber.

This can be achieved for example by arranging the air washing chamber to surround the plant chamber on all sides so that there is a large surface area able to carry air ingress aperture(s). Alternatively or in addition, in some embodiments, the or each plant chamber further comprises a lid formed of an air-impermeable material and having at least one plant aperture therein for the growth of plant(s) therethrough, the total surface area of the at least one plant aperture being less than the total surface area of the at least one ingress aperture of the respective air washing chamber The one or more panels of wicking material could be of any suitable construction and arrangement which ensures that the air flow through the air washing chamber will pass across and/or through one or more of the panels. The panels could be rigid and self-supporting but in preferred examples, the or each air washing chamber further comprises a support assembly configured to support the at least one panel of wicking material, the at least one panel of wicking material preferably being supported spaced from one another and from the walls of the air washing chamber. For instance, the wicking material could be a material such as synthetic felt or another material defining pores or other air-passages therethrough, which does not break down in water The support assembly could comprise one or more baffles, such as frames to which the wicking material is attached, or one or more cables (e.g. wires) suspended between walls of the air washing chamber over which the wicking material is draped or to which it is attached to create the panels. It should be noted that the panel(s) do not need to be planar (flat) or rigid, although such characteristics may be preferred.

The water reservoir for each air washing chamber could be provided outside the chamber and connection to the panels being made by suitable lengths of wicking material or similar. However, advantageously, the or each air washing chamber includes the respective water reservoir located at the base thereof and preferably under one of the ingress aperture(s) to allow replenishment of the water reservoir therethrough in use. For instance, the lowermost ends of the one or more panels may extend into the water reservoir The panel(s) may be arranged substantially vertically or at a non-90 degree angle to the horizontal to enable this.

Watering of the plants in the plant chambers could be done manually or with a separate system such as a sprinkler system. However, preferably, the or each planter unit further comprises an irrigation reservoir located beside or underneath the plant chamber for containing water in use, from which the growth substrate is supplied with water in use by capillary action. This is beneficial since the active nature of the system (having air drawn through the planter) may tend to lead to the plants and/or growth substrate becoming dry sooner than would be the case in a non-active system and hence manual watering would need to be performed very frequently to maintain plant health. The provision of such an irrigation reservoir is also a particularly good solution where the open surface area of the plant chamber is kept small (e.g. using a lid as mentioned above) to control the air flow. The growth substrate may be placed in contact with the water in the irrigation reservoir or a wick could be provided to connect the two.

In particularly preferred embodiments, the or each planter unit further comprises an irrigation access channel (e.g. a tube or top-up pipe) which bypasses the grown substrate for replenishing the irrigation reservoir in use, the irrigation access channel preferably including an opening to the environment or to the water reservoir of the air washing chamber For example, this could take the form of a tube extending to the open surface of the plant chamber, or a connection to the water reservoir of the air washing chamber. The latter arrangement is particular advantageous since both reservoirs can then be refilled by the user in a single action.

Preferably, the irrigation reservoir is located underneath the plant chamber and is divided therefrom by a base plate of the plant chamber which is perforated. This allows any rain or excess water to flow down to the irrigation reservoir and not saturate the growth substrate. Desirably, the base plate further includes one or more apertures through which respective wicking member(s) extend to make contact between the growth substrate and the water in the irrigation reservoir in use. This is desirable in order to avoid the growth substrate becoming saturated with water, which can damage the plants. It allows the planter to hold a set amount of water that the growth substrate can draw up as it starts to dry out via the connecting wicking members, which could be extensions of the growth substrate or additional lengths of wicking material. The base plate is preferably provided with one or more depressions (or "feet") at which the aperture(s) are located to allow for contact with the bottom of the irrigation reservoir. Preferably the depressions can also be used to seat the plant chamber within the planter unit leaving a space below to act as the irrigation chamber.

The air intake apparatus could take various forms, such as providing a plenum chamber beside or around a part of the or each plant chamber with suitable apertures, or an air-permeable wall, fluidicly connecting them. However, preferably the air intake apparatus comprises a respective air intake body for each planter unit, the or each air intake body comprising a housing having solid walls defining a hollow channel therewithin and a port into the channel, the solid walls having an array of apertures formed therethrough, each air intake body being configured to extend in use into the plant chamber of the respective planter such that the hollow channel is in fluid communication with the plant chamber via the array of apertures of the air intake body. The present inventor has found this arrangement to be most effective in directing the airflow to the root zone and allowing for a high flow rate. As such this further increases the efficiency of the air cleaning process. It should be noted that the air intake bodies could be formed integrally with the planter units or could be a separable component. Desirably, the air intake body is configured such that it extends within the plant chamber spaced from the walls thereof so that in use it is surrounded by growth substrate on all sides (except where connected at the port to the ducting system, manifold or other connector to the air flow generator).

Preferably, the system comprises a plurality of air intake bodies (e.g. one for each plant chamber, although more could be used), and a ducting system configured to connect each of the air intake bodies to the air flow generator, the ducting system extending between the ports of the air intake bodies and the air flow device. The use of a ducting system allows for a wide variety of configurations and significant design freedom. The ducting system preferably includes a control valve adjacent each connection to a port of an air intake body to enable shutting off of each air intake body independently. In this way, the number of air intake bodies (and associated planter units) in use can be varied at will.

The configuration of the or each air intake body may take various forms but preferable it is an elongate body, e.g. a cuboid, cylinder or polygonal prism, with a long axis which is greater than the width of the cross section perpendicular to that axis. The array of apertures could be localised on one side of the body, but more preferably, the array of apertures on the or each air intake body is arranged at least on two opposing walls of the air intake body. Most desirably, the array of apertures extends over substantially all of the walls of the air intake body, to allow for maximum air ingress. The individual apertures are preferably sufficiently small to prevent entry of growth substrate material or other solids into the interior of the air intake body. For instance, each individual aperture may be 2mm or less in width (e.g. diameter if they are circular). The apertures are preferably evenly spaced across the array. To further protect the system from blockages caused by ingress of growth substrate or plant material, preferably at least one, preferably each, of the air intake bodies further comprises a layer of filter material arranged adjacent the exterior of the housing of the air intake body and covering at least some, preferably all, of the array of apertures. Desirably this filter material may be hydrophobic so as avoid holding water and increasing air resistance.

The apertures on each air intake body should be of adequate number and size to allow for unrestricted air flow to match the capacity of the air flow generator, and to avoid increasing resistance to air flow in the system. For instance, each aperture may have a diameter of 2mm or less and desirably the apertures are evenly spaced across the air intake body. Ideally, the only air resistance in the system should be caused by the growth substrate density and the panels of wet wicking material in the air washing chamber (if air is caused to flow through them rather than across them). Hence, preferably, the total aperture area on the or each air intake body is equal to or greater than the internal cross-sectional area of the port of the respective air intake body. Preferably still, the total aperture area on the or each air intake body is equal to or greater than the minimum internal cross-sectional area through which the air flow passes upstream of the array of apertures before reaching the air flow generator.

Preferably, the or each air intake body is a removable air intake body configured to be inserted into a planter unit in use. That is, the air intake body is a separate component from the planter unit, allowing it to be taken out for cleaning and to allow easy access to the whole plant chamber for replanting. Desirably, he port of the or each air intake body may also be adapted for detachable connection to the air flow generator or to the ducting system. In a particularly preferred embodiments, the port connection between the air intake body and ducting system or other component of the air intake assembly is circular to allow the air intake body to be connected at various different orientations.

The specifications of the air flow generator should be sufficient to maintain a high air flow and to supply high enough fan pressure to overcome the natural resistance to air flow which will exist within the system. In preferred embodiments the air flow generator is configured to generate an air flow with a speed between 6 and 16 litres per second and/or a pressure of 500 to 2000 Pa. Suitable examples of air flow generators include fans, such as electric fans, with an appropriate power source. Generally a centrifugal fan will provide enough pressure to overcome resistance in the ducts and growth substrate. Whilst in some implementations, a single fan may be sufficient to achieve the necessary performance, in other cases it may be appropriate for the air flow generator to include two or more fans. The greater the size and/or number of the plant chambers, the greater the fan size and capacity that will be needed. In larger systems a multi-fan arrangement may be more efficient.

A benefit of the disclosed system is that its functionality can be increased if desired through the provision of one or more additional modules in the air stream. For instance, in some implementations the system further comprises a treatment chamber located between the air intake apparatus and the air flow generator A single treatment chamber could be provided at a location through which all the input air flows (from all of the planter units), or a dedicated treatment chamber could be provided for the air flow from each of one or more of the planter units. The treatment chamber preferably comprises an additive reservoir such as a perfume reservoir and/or a UV irradiation module, for example. Irradiation with ultra-violet light (UV) is known to kill bacteria and viruses which may be carried by the air stream and/or present on the interior of the system components.

The system may advantageously be equipped with sensors and appropriate output means to assist the user in the maintenance of the plants and/or achieve optimum air cleaning effects. For example, preferably, the or each planter unit further comprises a moisture sensor configured to detect the moisture level of the growth substrate in the plant chamber in use, and an output device for displaying the detected moisture level and/or transmitting the data to an external device. The output device could, for instance, comprise an indicator such as a light, on the plater unit or on an external device, which is activated should the moisture level fall below a certain threshold or could comprise a more complex display screen which shows a water content measurement, for example. If the output device is configured to transmit the data externally, an external device such as a computer, tablet, mobile phone or other portable device can be used to display or indicate the information, potentially through the use of a dedicated app. The system could alternatively or additionally include any of: a water level sensor (for the water reservoir and/or irrigation reservoir); a humidity sensor; a temperature sensor; a light level sensor; and/or an air quality sensor. In such cases, suitable output means will be provided to communicate the data from the or each sensor, which could be separate output devices for each sensor or a combined output means for indicating one or more of the data items, e.g. via a display screen located either on the system itself or on an external device if, for example, a dedicate app is provided.

The system could further comprise one or more motion sensors configured to switch off the system when no-one is in the vicinity (optionally after a time delay) to conserve power Detectors able to identify if the water supply and/or power supply are interrupted may also be provided and configured to issue an alert (e.g. via an app) if this occurs. The system may be configured to record adjustments made and parameters such as moisture level and/or air quality achieved, so that the system can be tracked and reviewed to monitor performance.

It will be appreciated that the air cleaning system will typically be supplied separately from the growth substrate and the plants, which will be added on site so that the system further comprises growth substrate located in the or each plant chamber and one or more plants rooted therein. The growth substrate (also termed growth medium) preferably comprises a sufficiently porous material which allows for airflow through the plant chamber and provides low resistance thereto. For example, the growth substrate could comprise engineered soil Such as an engineered green roof mixture could be used, which has a blend of sand, expanded clay pellets, and fine crushed brick with 20% organic materials included. Preferably the grit diameter is no larger than 10mm, and no smaller than 2mm. Alternatively, growth substrates such as those formed of man-made vitreous fibre could be used. In other examples, the growth substrate could comprise a mixture of materials such as organic compost, moss, bark etc. Any plants could be used and may be selected for aesthetic or other reasons, since typically it will be the naturally-occurring microbes associated with the plants in the root zone which perform the majority of the cleaning. However, in some cases it is advantageous to select plants which have specific phytoremediation properties such as mustard plants, alpine pennycress, hemp, and pigweed, which have been proven to have neutralising effects on certain toxins. In practice, the particular plants selected will depend on the site in question.

The system could be implemented as a free-standing unit. For instance, the system could comprise a single planter unit in which not only the plant chamber and air washing chamber are provided but also the air flow generator and the apparatus for directing air thereto as described above. This would be a compact implementation potentially having the appearance of a near-standard plant pot or planter. However in other preferred cases the system can be configured to be built into another structure or object, such as a piece of furniture, e.g. a desk or desk divider unit. In a particularly preferred embodiment, the system comprises a plurality of planter units, the planter units being arranged to form all or part of a wall. For instance, each planter unit could be elongate and fitted one above another into a suitable frame containing the ducting system and air flow generator Examples of air cleaning systems and methods in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 schematically shows an air cleaning system in accordance with an embodiment of the invention; Figure 2 is a flow diagram depicting steps in an exemplary air cleaning method in accordance with the invention; Figure 3A and 3B show an example of a planter unit and components located therein which may be used in embodiments of the invention, in perspective view and cross-section respectively; Figures 4 and 5 show two examples of air intake apparatus which may be used in accordance with embodiments of the invention, partially disassembled for ease of view; Figure 6 schematically shows an air cleaning system in accordance with another embodiment of the invention, equipped with growth substrate and plants; Figure 7 shows an example of material suitable for forming an air-permeable wall as may be used in embodiments of the invention; Figure 8 schematically shows an air cleaning system in accordance with a further embodiment of the invention; Figure 9 is a graph showing the results of two tests carried out on plant chambers as may be used in embodiments of the invention, equipped with growth substrate and plants, showing the concentration of NO2 in the test room over time (i) with the air flow generator switched off; and (ii) switched on at time 10:48; Figure 10 is a graph showing the results of two tests carried out on plant chambers as may be used in embodiments of the invention, equipped with growth substrate and plants, showing the concentration of (a) particles of less than 1 pm diameter ("PM1"), and (b) ultrafine particles of nanometer range diameter, in the test room over time (i) with the air flow generator switched off; and (ii) switched on at time 60 min; Figures 11A and 11B are graphs showing the results of two tests carried out on plant chambers as may be used in embodiments of the invention, equipped with growth substrate and plants, showing the particulate mass concentration A) in a chamber upstream of the plant chamber and B) in a chamber downstream of the plant chamber simultaneously, test particulates in the range PM 1 to PM10 being introduced to the upstream chamber at time 15:35 (approx.); and Figure 12 schematically depicts an air cleaning system in accordance with a further embodiment of the invention.

It will be appreciated that air cleaning systems such as those disclosed herein will typically be manufactured and supplied separately from the consumables with which the system must ultimately be equipped such as growth substrate, plants and water As such, the term "system" used herein does not include those consumables, except where otherwise specified. However, the Figures and description below make reference to those consumables in order to fully explain the functionality of the system in use.

Thus, Figure 1 schematically depicts a first embodiment of an air cleaning system 1, equipped with a growth substrate 40, plants 45 rooted therein, and water 30. Examples of suitable growth substrates which may be used include engineered soil, man-made vitreous fibre, organic compost, bark and so on. Desirably the grit diameter should be no more than 10mm and no less than 2mm. The growth substrate is preferably configured to have substantial porosity so as to allow for a significant airflow therethrough. Any type of plant 45 could be used but preferred examples include those mentioned above. In general plants will be selected based on the location (e.g. indoor vs outdoor, weather conditions) and on the size of the planter.

As shown in Figure 1, the system 1 includes a planter unit 5 which defines therein a plant chamber 6, which in use contains the growth substrate 40. In the example shown, the plant chamber occupies the whole of the planter unit 5 but as will be explained below this is not the case in all embodiments. There is an open area 7 of the plant chamber through which the stems, leaves and flowers of the plants extend and while this is typically on the upper surface of the planter unit 5 it could also be on a side thereof. The plant chamber is in fluidic communication with an air washing chamber 10 via a suitable conduit 9 such as an air-permeable wall, and with an air intake apparatus 2. The air intake apparatus 2 connects to an air flow generator 3, such as a fan, which is configured to draw air through the air-washing chamber 10 and the plant chamber 6 in use, and to expel it through an outlet 4.

Figure 2 sets out steps of an exemplary air-cleaning method which may be implemented using the system of Figure 1.

Thus, in step S101, air is drawn into the air-washing chamber 10 from the surrounding environment (the airflow is denoted in the Figures by the arrows labelled "AF"). The air-washing chamber 10 has at least one air ingress aperture 11 (here the entire top surface of the chamber is open) to allow air to enter the system 1. One or more panels 13 of wicking material are located in the air-washing chamber 10 and arranged to take water 30 from a water reservoir 12.

In the present example the water reservoir 12 is the lowermost portion of the chamber 10 itself although in other cases it could be located elsewhere with a suitable conduit (e.g. a length of wicking material) allowing water to be drawn therefrom by the panels 13. The one or more panels 13 are arranged so that as air flows through the air-washing chamber 10, it travels through and/or across one or more of the panels 13, thereby interacting with the water held by the wicking material forming the panels 13 (step S102).

Next, in step S103, the moistened air is drawn by the air flow generator 3 from the air-washing chamber 10 into the plant chamber 6 and through the growth substrate 40 located therein, where it interacts with the plants 45 and the microbes existing primarily at the root zones of the plants (step S104). On exiting the plant chamber 6 into the air intake apparatus 2, the processed air is then drawn to the air flow generator 3 and expelled at outlet 4 (step S105).

As explained above, the interaction between the air and the water in air-washing chamber 10 moistens the air and starts to break down toxins carried by the air, particularly NO2. The water may also have a further cleaning effect, trapping certain toxins and retaining them in the water. The pre-moistening of the air increases the effectiveness of the phytoremediation process which then takes place in the plant chamber 6. In particular, the partial dilution of the toxins by the water allows the microbes to better adhere and breakdown the remaining toxins in the air molecules as they pass through the growth substrate. Thus, the air expelled by the system 1 at output 4 is cleaner than the air which enters the system 1 from the environment. This means that the concentration of pollutants (e.g. toxins such as volatile organic compounds and/or particulates such as dust) in the air exiting the system 1 is reduced relative to that in the air entering the system 1. The results of test illustrating this effect will be discussed below. It has also been found that any odours which may arise as a result of water sitting in reservoir 12 are removed by the cleaning process which takes place in plant chamber 6.

Optionally, the system could be provided with additional functionality such as the addition of a scent (perfume), or sterilization of the air flow by UV irradiation. This can be achieved by providing a treatment chamber upstream of the plant chamber 6. In the example shown in Figure 1, a section of the air input apparatus 2 is used to act as the treatment chamber, namely the section surrounding treatment device 50. The treatment device 50 could comprise, for example, a perfume reservoir (or spray unit), or a UV light source. In other cases, the treatment device could comprise an additional filter, such as a washable filter, to further remove particulates from the air flow. Preferably an access door (not shown) is provided to the treatment chamber to allow for easy replenishment and/or maintenance of the treatment device 50.

It will be noted that since the plant chamber 6 is open to the environment at area 7, there may also be some ingress of air directly into the plant chamber. VVhilst this will not eliminate the beneficial effects of the air-washing chamber 10 (since at least some of the air flow will travel through air-washing chamber 10), it is desirable to have the air ingress through open area 7 make up a minor proportion of the air flow through system 1 (i.e. less than 50%). This can be achieved by a variety of means including arranging the surface area of opening 7 to be less than that of the air ingress aperture(s) 11 and/or through controlling the density of the growth substrate which could be configured to have a higher density (and thus air resistance) adjacent opening 7 than adjacent conduit 9, to act as a barrier In some embodiments it may be appropriate to provide an air-impermeable lid as will be described below.

Figures 3A and 33 show an example of a planter unit 5 which defines both a plant chamber 6 and an air-washing chamber 10 therewithin. The planter unit 5 is generally of elongate cuboidal shape, with its long dimension along the x-axis in this example. Here, the z-axis is the vertical axis. The cross-sectional dimensions in the z and y axis are smaller than the length of the planter unit in the x-axis. The plant chamber 6 occupies a middle portion of the planter unit 5 in the transverse (y-axis) direction and is sandwiched between portions of the air-washing chamber 10 on either side. Thus, the top surface of the planter unit 5 is divided into three parts (which may be of equal or non-equal area): the middle part is the open area of As shown in the perspective view of Figure 3A, this allows the total area 7 of plant chamber 6 while the two outer parts provide the ingress apertures 11 of air-washing chamber 10. In this way the open area 7 of plant chamber 6 is less than the total area of the ingress apertures 11 which leads to an increased proportion of the airflow having passed through the air-washing chamber 10.

The cross-section of Figure 3A shows the construction of planter unit 5 in more detail. The planter unit 5 is bounded on three sides by external walls 5a which may be made of any suitable water-impermeable material such as plastics or metal. The top surface is open. Inside the planter unit 5 is the plant chamber 6 defined by walls suitable for containing the growth substrate inside the plant chamber in use. In this case at least portions of the walls are formed of air-permeable dividers 9, which allow air to pass through. Suitable constructions will be described below. Preferably the walls are water-impermeable, most preferably hydrophobic, to avoid the walls 9 carrying water which would increase air-resistance The base plate 6a (which may be integral with the walls) of the plant chamber 6 desirably includes at least one aperture 6c therethrough to enable water to be transferred into the plant chamber 6 from an irrigation reservoir 8 which in this example is located under the plant chamber 6 and is filled with water 30 in use.

Preferably, the base plate defines one or more "feet" 6b which are depressions extending into the reservoir 8. If one or more of the apertures 6c are provided in the region of the "feet" this enables access to the water in reservoir 8 even when the level of water is low. The "feet" 6b may also contact the base of planter 7 in which case they can also act as a structural support to plant chamber 6. In this example the growth substrate 40 is thus placed in direct contact with the water 30 in reservoir 8 through the apertures 6c such that it can draw in water by capillary action. In other cases, suitable wicks might be provided to make the contact between the growth substrate and the water.

To each side of plant chamber 6 (in the y-axis direction) is located a portion of air-washing chamber 10. As already mentioned, the top of these chambers are open and form the air ingress apertures 11. In the air-washing chamber 10 are located one or more (here, a plurality of) panels 13 of wicking material, such as synthetic felt. Each panel 13 is placed in contact with a water reservoir 12 (either directly or via one of the other panels 13) which contains water 30 in use, so that the panels 13 remain wet. Advantageously, the panels 25 have a maximum height above the water level of no more than 25cm, since it has been found that panels with a greater height are less efficient at drawing up water and hence less effective. The panels 13 are arranged so that air entering the planter unit through the ingress apertures 11 will pass through and/or across the panels en route to the air-permeable wall 9 where it enters the plant chamber. In this example, the panels 13 are arranged in substantially vertical planes, spaced from one another and from the walls 5 of the planter as well as from air-permeable wall 9. This maximises the interaction between the airflow and the wet panels in use. The panels 30 may be free-standing if their material is sufficiently rigid and self-supporting. Alternatively, as in the case shown, a support structure 14 may be provided to support the panels in position. The support structure 14 may comprise a frame or baffle to support the wicking material, or could comprise or more cables or wires (one of which is depicted in Figure 33) to which the wicking material is attached or over which the wicking material is draped.

It should be noted that in this case the water reservoir 12 of the air washing chamber 10 and the irrigation reservoir providing water to the growth substrate 40 are continuous and both formed by the base of the planter unit 5. Thus refilling the water reservoir 12 (through the ingress apertures 11, which are above the reservoir 12) will automatically also fill the irrigation reservoir 8. This is advantageous but may not be the case in all embodiments, noting in particular that the irrigation reservoir 8 is optional and could be left out (in which case irrigation of the plants would be done manually or with a sprinkler system).

The present embodiment also makes use of a particularly preferred implementation of air intake apparatus 2. In the previous example shown in Figure 1, the air intake apparatus 2 is fluidicly connected to the plant chamber 6 through one of the walls of the plant chamber, in a manner similar to a plenum chamber. However, the present inventor has found that superior results are achieved if air is drawn into the air intake apparatus inside the plant chamber 6. This can be achieved through the use of one or more air intake bodies 22, or inserts, which are fitted inside the plant chamber 6. Figure 3B shows one such air intake body 22 in cross section and its construction will be described further in relation to Figure 4. The air intake body 22 is not visible in Figure 3A since it is covered by the growth substrate 40 shown. The air intake body is a hollow component with solid walls having an array of apertures 23 formed therethrough. The air intake body is connected at a port thereof to the air flow generator via an appropriate conduit as will be described further below. The port or conduit may exit the planter unit through an appropriate dedicated opening such as that labelled 21 in Figure 3A, or through the open area 7.

In use, the air flow generator causes air to be drawn in through the air intake body 22 as depicted by the arrows AF in Figures 3A and 3B. As before, the air (preferably a majority thereof) enters the system from the environment through the air-washing chamber 10 where it interacts with wet panels 13 before entering the plant chamber 6 where it encounters the plants and associated microbes and undergoes phytoremediafion. The air is drawn into the air intake body and then exits the planter unit 5 for onward travel towards the air flow generator before being output. By locating the air intake body 22 inside the plant chamber 6, preferably surrounded by the growth substrate 40 on all sides (except at the port), the air flow is better directed to the root zone of the plants. Further, a large surface area can be utilised for intake of air: preferably the array of apertures 23 extends over all surfaces of the air intake body, although this is not essential.

The array might, for instance only be arranged on two opposing surfaces, such as the long surfaces shown in Figure 3B which run parallel to the air-permeable walls 9 -this helps encourage the air flow to pass through the air-washing chambers rather than enter directly into the plant chamber 6 at open area 7. The apertures 23 in the walls of the air intake body 22 are preferably each sufficiently small so as to prevent ingress of solids such as parts of the growth substrate and/or plant material, to avoid the system becoming blocked.

Optionally, a filter material layer 26 may be arranged outside the apertures to further assist in this. The filter material is air-permeable and preferably hydroponic to prevent it becoming waterlogged and adding to any air resistance.

The embodiment shown in Figures 3A and 3B also includes an optional moisture sensor 55 which is arranged to contact the growth substrate in use. This is depicted as a separate component but in practice may be fixed into the planter unit 5. The moisture sensor is of a known sort and detects the water content within the growth substrate either continuously or at regular intervals. The moisture sensor 55 is connected to an output device such as light 56 which can be used to indicate the moisture level, e.g. by being switched on when the water content falls below a certain level. The sensor includes a controller and power source as necessary to control the light 56 in response to the detected water content level. In other cases, a more complex output system may be provided, such as a processor for digitally processing the moisture data and a display for displaying the measured value. Alternatively or in addition, the output system could include a (wired or wireless) transmitter for transmitting data relating to the moisture level to an external device such as a computer, tablet or mobile phone which may be equipped with a dedicated app for display of the information.

Remote operation via such an app (or other external means) allows the user to reset operating times and parameters without needing to be on site, as well as to activate and switch off the system as required. Environmental or air quality data, e.g. measured by sensors in the system, can also be recorded.

If the air cleaning system includes multiple such moisture sensors (e.g. one for each of a plurality of plant chambers), they may be connected to a central processor associated with the air cleaning system which communicates with an output device for the whole system. Alternatively or additionally, other sensor types may be deployed in the system and likewise configured to communicate the data they measure either via corresponding separate indicators or via the same display as mentioned above, e.g. using an app on an external device.

Examples of other sensors which may be provide include a water level sensor (for the water reservoir and/or irrigation reservoir); a humidity sensor; a temperature sensor; a light level sensor; and/or an air quality sensor. Preferably, the app allows for full visibility and control of one or more air cleaning systems whilst logging all data received from them. Alerts can be added to inform the user of any anomalies.

Figure 4 shows an example of an air intake apparatus 2 which includes one or more air intake bodies 22 of the sort discussed in relation to Figure 3B. In Figure 4, only one air intake body 22 is shown, for clarity, but more will typically be provided in practice. In addition to the air intake body(ies), the air intake apparatus 2 comprises a ducting system formed of a manifold 24 into which each air intake body 22 is connected at its port 25. The manifold 24 is a hollow body with appropriate apertures and connectors for attaching to the ports 25 of the or each air intake body 22, and a section housing the air flow generator 3 which also defines outlet 4. The connections are configured to enable the various air intake bodies and associated planter units to be arranged beside one another with the result that, in this example, together a set of planter units 7 (each such as that shown in Figure 3A) will produce a horizontal "bed" of plants.

For instance, in this example a second and third air intake body (each identical to that shown) can be fitted into apertures 25' and 25" of the manifold. In Figure 4 it is also possible to see the air intake body 22 removed from the planter unit and it will be noted that, in this example, it takes the form of an elongate cuboid although in other cases it could be cylindrical or any polygonal prism, for instance. The dimensions of the air intake body in this example are: di = 30mm, d2 = 100mm. The array of apertures 23 is shown highly schematically. Typically the air intake body is formed of a plastics material such as ABS or polypropylene, or some other non-corrodible material.

An alternative example of air intake apparatus 2 is shown in Figure 5. This has the same basic construction as that described with reference to Figure 4, being formed of a ducting system 24 into which multiple air intake bodies 22 can be connected, and a section for air flow generator 3 and outlet 4. In this case the ports 25 are circular which allows each air intake body 22 to be connected into the ducting system in any orientation. Hence whilst the apparatus 2 is shown configured for vertical deployment, with air intake body 22a above air intake body 22b, and so on (suitable for forming into a "living" or "green" wall, for instance), the same components could instead be arranged into a horizontal configuration (similar to that shown in Figure 4) if desired. Another example of how the systems disclosed herein can be configured to form a wall structure will be described below with reference to Figure 12. Systems of the sort described in any of the embodiments herein (using one or multiple planters) can also be deployed in other structures, such as incorporated into or onto furniture such as desks, e.g. forming desk divider units.

A further embodiment of an air cleaning system 1 is depicted schematically in Figure 6. Only one planter unit 5 is shown, for clarity, but in practice a plurality of such units may be provided in the manner just described with reference to Figures 4 and 5. Like reference numerals are used to denote equivalent components to those already described with reference to Figures 1 to 5 and the same considerations disclosed above apply equally to the components here.

Where the air intake bodies 22 connect to the ducting 24, control valves 25a may be provided so that the number of active planters can be easily varied.

As in the Figure 3 example, here the plant chamber 7 and air washing chamber 10 are both defined within the planter unit 5. However, in this case the air washing chamber 10 is located at one end of the planter unit 5, furthest from the end at which the port of air intake body 22 connects into ducting 24. As before, an air-permeable wall 9 divides the air-washing chamber 10 from the plant chamber 6. An example of a suitable construction for the air-permeable wall 9 is shown in Figure 7, and is a sandwich arrangement having a central core 9b of plastic fibres, knitted or otherwise interconnected to form a mesh, weave or other 3D structure with wide channels therethrough to allow for the passage of air. A layer of filter material 9a is provided on each side of the core to prevent the movement of solid material therethrough. Preferably the wall 9 is not absorbent to water, most preferably hydrophobic, so that it does not become waterlogged and impede the passage of air therethrough.

In the Figure 6 embodiment, an optional irrigation reservoir 8 is again provided beneath the plant chamber 6 and the arrangement for transferring water 30 from there into the growth substrate 40 is the same as discussed in relation to Figure 38. However, in this case the irrigation reservoir 8 is separate from the water reservoir 12 in the air-washing chamber 10. Therefore, preferably, a channel 8a is provided for refilling of the irrigation reservoir B. The channel 8a comprises a tube or similar which conveys water to the reservoir 8 while bypassing the growth substrate so as to avoid over-saturation thereof. In other examples, a filling channel could instead be arranged to connect the irrigation reservoir 8 to the water reservoir 12 through the wall 9 so that water will transfer from one to the other, with the result that both can be filled by topping up the air-washing chamber.

In this example it will be noted that the surface area of air ingress aperture 11 is smaller than the open area 7 of the plant chamber 6 through which the plants 45 grow. Depending on the relative air resistance offered by the growth substrate 40 and the panels 13, this may lead to an undesirably large portion of the air flow bypassing the air-washing chamber 10 and entering the system directly through the plant chamber 6. To mitigate this, an optional lid component 6' (shown removed from the system in Figure 6) may be provided to reduce the effective open area 7 of the plant chamber. The lid 6' is formed of an air-impermeable material such as plastic sheet and is designed to fit over the whole open area 7. Apertures 6" are provided in the lid to enable the plants 45 to grow therethrough.

In this way the open area of plant chamber 6 can be significantly reduced without impacting on the growth of the plant. If desired, the lid 6 can be concealed by covering it with another layer of (real or artificial) growth substrate.

Figure 8 shows another embodiment of an air cleaning system 1, in cross-section. This implementation varies from those described immediately above in that a single planter unit 5 is provided and is intended to act as a standalone unit, with an appearance close to that of a traditional plant pot. It will be noted that the cross-section is similar to that of the planter unit 5 shown in Figure 3B, and the functionality is indeed the same. Like reference numerals are used to denote equivalent components. The air-washing chamber 10 in this case is arranged to encircle the plant chamber 6 on all lateral sides, and an air-permeable wall is provided to divide the two. Air ingress apertures 11 are provided on the external walls 5a of the planter unit 5. A panel 13 of wicking material is also arranged to encircle the plant chamber 6 in the air-washing chamber, preferably spaced from the walls. As before this may be provided with a suitable support. The panel 13 takes water from water reservoir 12, which is continuous with irrigation reservoir 8 under the plant chamber 6. In this example, rather than build "feet" into the base plate 6a of the plant chamber 6, a portion of the growth substrate (or a wick) extends from the interior of the plant chamber 6 to the irrigation reservoir 8 to enable delivery of water to the growth substrate 40.

The primary difference in this embodiment lies in the implementation of the air intake apparatus 2, which in this case takes the form of a small, hand held unit which can be pushed into the growth substrate 40 by a user. The unit includes an air intake body 22 which in this example is cylindrical and once again is hollow with solid walls having an array of apertures 23 therethrough, preferably on all sides. The air intake body 22 is directly connected to a housing 3a containing an air flow generator 3 such as a fan, and defining an output 4 through which air is expelled. The air flow generator may be battery-powered and suitable control switches will be provided on the housing 3a.

In use, upon activing the air flow, air is drawn into the system 1 through the air ingress apertures 11, into the air washing chamber 10 where it interacts with water in the panel 13 before passing through the wall 9 into the plant chamber 6.

The air is then drawn in through the air intake body 22 and expelled via output 4.

This configuration has the advantage that it is compact and can be quickly deployed in any environment.

Optionally, the system may be provided with a moisture sensor 55 and output device 56 as already described with reference to Figure 3B, which may or may not include a communications module for transmitting the data to an external device. A lid (not shown) could also be provided to reduce the open surface area 7 if desired.

To demonstrate the effectiveness of plants and their associated microbes in removing air pollutants, a prototype assembly was tested in a sealed measure its ability to remove the following pollutants from the air: room to * Nitrogen dioxide (NO2) * Total volatile organic compounds (TVOC) * MEK (methyl ethyl ketone or butan-2-one) * Toluene * Limonene * Particulates The prototype assembly comprised three planter units, each equipped with an air intake body 22 of the sort shown in Figures 4 and 5, connected to a ducting system 24 such as that shown in Figure 4. The ducting system housed two fans with (collectively) a minimum fan speed of 25 cubic meters per hour and a maximum pressure of 550 Pa. The total open surface area of the three plant chambers was 0.5 square meters, and collectively the plant chambers contained litres of growth substrate with 15 plants rooted therein. The growth substrate used in this example was "Optigreen Intensive Substrate l" available from Optigreen Limited and comprising expanded shale, expanded clay, lava, pumice, crushed brick, Porlith and green waste compost, and having a total pore volume of 60 to 75 voN/0. The plants were a selection of herbaceous plants incuding ferns and groundcovers. Note that for the purposes of these tests, no air-washing chamber was provided so the results demonstrate the effectiveness of the phytoremediation process without enhancement by pre-moistening the air. However it will be appreciated that if an air-washing module were provided the reduction in pollutants achieved by the system would be even greater than the results discussed below.

The prototype system was set up in a 30m2 sealed chamber with the room ventilation switched off. The following substances and parameters were monitored using appropriate sensors: * CO2 concentration, temperature and relative humidity (monitored continuously) * NO and NO2 concentration (monitored continuously) * TVOC concentration, expressed as toluene as per convention, and individual VOCs prsent, measured by pumped ("active") adsorbant tube sampling over separate periods of 30 minutes. The components were identified by mass spectrometry and concentrations analysed by thermal desorption and gas chromatography.

* Particulates of less than 1 micron, less than 2.5 microns and less than 10 microns respectively (PM1, PM2.5 and PM10), measured continuously.

* Ultrafine particles in the size range 0.02 to 1 micron, measured continuously.

To test the removal of VOCs, some common indoor VOCs were introduced into the chamber via a "doping chamber" located in the air supply to the 30m2 chamber and the environment in the chamber was allowed to stabilise overnight.

Once stable, the air supply was shut down and the chamber sealed before testing began. Toluene, limonene and MEK were used for these test. The VOC levels were measured three times in the centre of the chamber and at the chamber outlet during the 4 hour test phases when the prototype was either inactive or active, as appropriate for the test.

To test for the removal of NO2, a source of NO2 was introduced to the sealed chamber and the concentration monitored. Once the concentration in the chamber reached a required level the source was switched off and the testing phase begun.

Figure 9 is a graph showing the measured concentration of NO2 in the chamber during two tests. In test (i), the prototype system remained off all day, whereas in test (ii) the system was switched on shortly before 11am (marked by the vertical line. It will be seen that the source of NO2 was introduced at about 8.30am, raising the NO2 concentration to about 130 ppb. Since NO2 reacts to surfaces its concentration level in the chamber atmosphere is expected to decay naturally over time, and this is what is seen in trace (i), where the prototype system is not activated. As shown by trace (ii), however, once the prototype system was activated, the NO2 concentration level decreased much more rapidly. The rate of fall is 2Oppb (parts per billion) every 20 minutes, since the system took the concentration from 90 ppb to 15 ppb in 1.5 hours. This is equivalent to just over a single air change per hour, based on the maximum fan speed of 25 m3 per hour (taking into account the 30 m3 volume of the test room). Most preferably the air flow rate should be sufficient to exchange the volume of air in the space in question at least once every hour, so in this case a slightly higher volume fan with five more plants would have produced even better results.

Figure 10 is a graph showing the measured concentration of certain particulates 30 in the test room over time -the two traces marked (a) show concentrations of PM1 particulates (diameter less than 1 micron) and those marked (b) show concentrations of ultrafine particles (diameters down to 0.02 nm). In the first test, depicted by the traces marked (i), the prototype system was left inactive throughout. In the second test, represented by the traces marked (ii), the prototype system was switched on at time = 60 mins. Over time, particulates will settle on surfaces and so it is expected to see a natural decay in the particulate concentration. However it is clear from traces 00(a) and (ii)(b) that when the prototype was switched on the rate of concentration deva increased, especially for particles in the PM1 particle mass-fraction.

The results of the VOC tests is shown below in Tables 1 and 2. Table 1 shows measurements taken during a first test, the prototype system remaining inactive throughout. Table 2 shows measurements taken during a second test, with the prototype system being switched on during the test. Note in both tables, TVOC is quantified as toluene so TVOC may not equal the sum of the individual VOCs.

Table 1

Prototype status Sampling time VOC concentration (pg/m3) TVOC MEK Toluene Limonene OFF 09.28-09.58 732 250 443 126 OFF 10.48-11.18 680 214 404 111 OFF 12.08-12.38 648 200 391 114

Table 2

Prototype status Sampling time VOC concentration (pg/m3) TVOC MEK Toluene Limonene OFF 09.15-09.45 705 278 425 99 ON 10.35-11.05 608 208 372 96 ON 11.55-12.25 464 117 296 76 It will be seen from the results that, even with the prototype switched off (Table 1), there was a slight reduction in each VOC and the TVOC over time, since the substances adsorb onto surfaces and may also react with the NO2 in the atmosphere. However, turning the prototype on is shown to significantly reduce the amount of each substance. In the case of TVOC this was by 45% within one hour of the prototype being switched on, and MEK reduced by 55% in the same time.

A second set of tests was carried out using the same prototype system (though with a single planter and air intake body, and a fan of speed 8 litres per second and pressure of 2000PA in place of the two fans mentioned above) in relation to particulate removal. In this case, instead of placing the prototype in a sealed room, the measurements were made in two test chambers, each with a volume of 1 m3, the first test chamber (A) being located upstream of the prototype and thus representative of the air entering the system, and the second test chamber (B) being located downstream of the prototype, representative of the air exiting the system. The concentration of particulates at each of the following mass fractions was measured in each chamber over time: PM1, PM2.5, PM4 and PMio, using sensors calibrated against one another to within 3% accuracy, and the results are shown in Figures 11A and 11B. Figure 11A shows the measurements in chamber A (upstream), to which sample particulates were introduced around time 15.35. The prototype was switched on at time 15.36 and it can be seen that the particulates were quickly drawn into the system leaving substantially zero concentration of particulates in chamber A by time 15.44. In the downstream chamber B (Figure 11B), it can be seen that a peak concentration of around 75 pg/m3 was detected shortly after switching on of the unit. This value is already substantially lower than the 200 pg/m3 concentration that was introduced to the system (see Figure 11A) which demonstrates the immediate effectiveness of the system. Both clambers were then cleaned to a very low concentration of particulates (around 5 pg/m3 within 5 minutes. This rate if applied to a 30m3 space would clean the room of 100% of particulates with 75 minutes.

Figure 12 schematically depicts a further embodiment of an air cleaning system in which multiple units are arranged to form a wall structure. In the example shown, there are four planter units 55, 56, 57 and 58 arranged one above the other as shown. Each planter unit includes a plant chamber 6 containing growth substrate 40 in which plants 45 are rooted (only the uppermost planter 55 is depicted as containing plants, for clarity, but in practice it is preferably to put plants in all units). An air washing chamber 10 is provided at a first end of each planter unit, including an inlet 11 for air ingress (the arrows marked A denote the air flow). Inside the air washing chamber 10 is at least one panel 13 of wicking material as described in previous embodiments, and a water reservoir 12 supplying water to the panel(s) 13. An irrigation reservoir 8 extends underneath each plant chamber 6, divided therefrom by perforated base 6a as in previous embodiments. The two reservoirs can be filled up by supplying water W to the system 1 via an opening in the uppermost planter unit. This could be by connection to the mains or by manual means. An overflow opening is provided in each unit so that when the water in the reservoir reaches a certain level, excess water exits via the overflow and is fed to the next planter unit, and so on. In this way all of the units can be provided with water via a single point. The flow of water W through the system is indicated by the arrows marked W. At the second end of the plant chamber 6, the unit connects to a duct leading to air flow generator 3 (e.g. a fan) and outlet 4. The walls 9 at the first and second ends of the plant chambers 6 are air-permeable as in embodiments described above. As such, in use, the fan 3 draws air in through inlets 11, via the air washing chambers 10, through the plant chambers 6. The air is then expelled via outlet 4, having been purified by the air washing chamber and interaction with the plants and microbes in plant chambers 6 as already explained above. It should be noted that whilst in this example, air inlet bodies such as items 22 discussed in previous embodiments are not essential, it may be preferred to add such inlets and connect them into the duct in the manner of Figure 5, for instance.

The structure may if necessary be supported in or on a frame (not shown) and could be freestanding or attached to another structure, such as the wall of a building (internal or external).

Claims

CLAIMS1. An air cleaning system, comprising: one or more planter units, each planter unit defining therewithin at least a plant chamber adapted to contain a growth substrate and plant(s) in use; an air intake apparatus, fluidicly connected with the interior volumes of the or each plant chamber; an air flow generator, fluidicly connected to the air intake apparatus and configured to draw air in to the air cleaning system, and to expel the air through an outlet; characterised in that a respective air washing chamber is provided upstream of each plant chamber and fluidicly connected therewith, each air washing chamber including at least one ingress aperture for air ingress from the environment and comprising therein one or more panels of wicking material in contact with a water reservoir such that the one or more panels of wicking material carry water in use, the one or more panels being configured such that the air flow passes across and/or through the one or more panels; whereby, in use, air drawn into the air cleaning system by the air flow generator passes first through an air washing chamber and second through a plant chamber, such that the air expelled through the outlet is cleaned as a result of both interaction with the water carried by the panel(s) of wicking material and by the moistened air subsequently passing through a growth substrate material located in the plant chamber in use.
2. An air cleaning system according to claim 1 wherein the or each air washing chamber is defined in the respective planter unit.
3. An air cleaning system according to claim 2, wherein in each planter unit, the air washing chamber and the plant chamber are divided by an air-permeable wall, the air-permeable wall preferably being formed of a material which is hydrophobic.
4. An air cleaning system according to claim 2 or 3, wherein in each planter unit, the air washing chamber is located at a first end of the planter unit, and the air intake apparatus is connected to the plant chamber at a second, opposite end of the planter unit.
5. An air cleaning system according to claim 2 or 3, wherein in each planter unit, the air washing chamber is located on at least two, preferably all, sides of the plant chamber.
6. An air cleaning system according to any of the preceding claims, wherein any open surface area of the or each plant chamber in communication with the environment is configured to be less than the open surface area of the at least one ingress aperture of the respective air washing chamber
7. An air cleaning system according to any of the preceding claims, wherein the or each plant chamber further comprises a lid formed of an air-impermeable material and having at least one plant aperture therein for the growth of plant(s) therethrough, the total surface area of the at least one plant aperture being less than the total surface area of the at least one ingress aperture of the respective air washing chamber
8. An air cleaning system according to any of the preceding clams, wherein the or each air washing chamber further comprises a support assembly configured to support the at least one panel of wicking material, the at least one panel of wicking material preferably being supported spaced from one another and from the walls of the air washing chamber
9. An air cleaning system according to any of the preceding clams, wherein the or each air washing chamber includes the respective water reservoir located at the base thereof and preferably under one of the ingress aperture(s) to allow replenishment of the water reservoir therethrough in use
10. An air cleaning system according to any of the preceding clams, wherein the or each planter unit further comprises an irrigation reservoir located beside or underneath the plant chamber for containing water in use, from which the growth substrate is supplied with water in use by capillary action.
11. An air cleaning system according to claim 10, wherein the or each planter unit further comprises an irrigation access channel which bypasses the grown substrate for replenishing the irrigation reservoir in use, the irrigation access channel preferably including an opening to the environment or to the water reservoir of the air washing chamber.
12. An air cleaning system according to claim 10 or 11, wherein the irrigation reservoir is located underneath the plant chamber and is divided therefrom by a base plate of the plant chamber which is perforated, the base plate preferably including one or more apertures through which respective wicking member(s) extend to make contact between the growth substrate and the water in the irrigation reservoir in use, wherein the base plate is preferably provided with one or more depressions at which the aperture(s) are located to allow for contact with the bottom of the irrigation reservoir.
13. An air cleaning system according to any of the preceding claims wherein the air intake apparatus comprises a respective air intake body for each planter unit, the or each air intake body comprising a housing having solid walls defining a hollow channel therewithin and a port into the channel, the solid walls having an array of apertures formed therethrough, each air intake body being configured to extend in use into the plant chamber of the respective planter such that the hollow channel is in fluid communication with the plant chamber via the array of apertures of the air intake body..
14. An air cleaning system according to claim 13, comprising a plurality of air intake bodies, and a ducting system configured to connect each of the air intake bodies to the air flow generator, the ducting system extending between the ports of the air intake bodies and the air flow device, the ducting system preferably including a control valve adjacent each connection to a port of an air intake body to enable shutting off of each air intake body independently.
15. An air cleaning system according to claim 13 or 14, wherein the array of apertures on the or each air intake body is arranged at least on two opposing walls of the air intake body.
16. An air cleaning system according to any of claims 13 to 15, wherein the total aperture area on the or each air intake body is equal to or greater than the internal cross-sectional area of the port of the respective air intake body.
17. An air cleaning system according to claim 16, wherein the total aperture area on the or each air intake body is equal to or greater than the minimum internal cross-sectional area through which the air flow passes upstream of the array of apertures before reaching the air flow generator.
18. An air cleaning system according to any of claims 13 to 17, wherein at least one, preferably each, of the air intake bodies further comprises a layer of filter material arranged adjacent the exterior of the housing of the air intake body and covering at least some, preferably all, of the array of apertures.
19. An air cleaning system according to any of claims 13 to 18, wherein the or each air intake body is a removable air intake body configured to be inserted into a planter unit in use.
20. An air cleaning system according to any of claims 13 to 19, wherein the port of the or each air intake body is adapted for detachable connection to the air flow generator or to the ducting system.
21. An air cleaning system according to any of the preceding claims, wherein the air flow generator is configured to generate an air flow with a speed between 6 and 16 litres per second and/or a pressure of 500 to 2000 Pa.
22. An air cleaning system according to any of the preceding claims, further 10 comprising a treatment chamber located between the air intake apparatus and the air flow generator, wherein the treatment chamber preferably comprise an additive reservoir such as a perfume reservoir and/or a UV irradiation module.
23. An air cleaning system according to any of the preceding claims, wherein the or each planter unit further comprises a moisture sensor configured to detect the moisture level of the growth substrate in the plant chamber in use, and an output device for displaying the detected moisture level and/or transmitting the data to an external device.
24. An air cleaning system according to any of the preceding claims, further comprising growth substrate located in the or each plant chamber and one or more plants rooted therein.
25. An air cleaning system according to any of the preceding claims, comprising a plurality of planter units, the planter units being arranged to form all or part of a wall.
26. A kit of parts, comprising: one or more planter units, each planter unit defining therewithin at least a plant chamber adapted to contain a growth substrate and plant(s) in use; an air intake apparatus, an air flow generator, a respective air washing chamber including at least one ingress aperture for air ingress from the environment and comprising therein one or more panels of wicking material in contact with a water reservoir such that the one or more panels of wicking material carry water in use, the one or more panels being configured such that the air flow passes across and/or through the one or more panels; which once assembled forms an air cleaning system in accordance with any of claims 1 to 25.
27. An air cleaning method, comprising: providing one or more planter units, each planter unit defining therewithin at least a plant chamber having a growth substrate and plant(s) rooted therein; providing an air intake apparatus, fluidicly connected with the interior volumes of the or each plant chamber; providing a respective air washing chamber upstream of each plant chamber and fluidicly connected therewith, each air washing chamber including at least one ingress aperture for air ingress from the environment and comprising therein one or more panels of wicking material in contact with a water reservoir containing water such that the one or more panels of wicking material carry water, and using an air flow generator, fluidicly connected to the air intake apparatus, to draw air in to the air cleaning system, and to expel the air through an outlet; whereby air is drawn into the air cleaning system by the air flow generator and passes first through an air washing chamber across and/or through the one or more panels, and second through a plant chamber, such that the air expelled through the outlet is cleaned as a result of both interaction with the water carried by the panel(s) of wicking material and by the moistened air subsequently passing through the growth substrate material located in the plant.
28. An air cleaning method according to claim 27, performed using the air cleaning apparatus of any of claims Ito 25.