WO1998055807A1

WO1998055807A1 - Methods and apparatus for elimination of house dust mite

Info

Publication number: WO1998055807A1
Application number: PCT/GB1998/001617
Authority: WO
Inventors: Kenneth Houlbrook
Original assignee: Mediclean Corporation Ltd.
Priority date: 1997-06-06
Filing date: 1998-06-03
Publication date: 1998-12-10
Also published as: GB9711692D0; AU7779598A

Abstract

Unless measures are taken, textile furnishings of bedrooms are infested with dust mites and their allergens, which cause asthma sufferers considerable distress. In order to relief this asthma sufferer, an environment, specifically a bedroom (18) in a building, has its atmosphere controlled. This is achieved by controlling the humidity to a level not exceeding 55 % at which the mites cannot exist and/or by treating textile furnishings to kill the mites and their allergens, and/or by changing the air by introducing fresh air at a high level in the room (18) and removing stale air from a low level in the room (18).

Description

METHODS AND APPARATUS FOR ELIMINATION OF HOUSE DUST MITE

This invention relates to improvements in the field of controlled environments, and more specifically to methods of controlling environments which are inhabited by sufferers of asthma, and related respiratory and other conditions which it is believed are exacerbated by the house dust mite (HDM) and its allergens.

Medical evidence has suggested that the allergens of the HDM, present in the faeces thereof, contribute to the suffering of asthmatics and persons with like respiratory conditions, (see M J Bluff "Use of Liquid Nitrogen in the Control of House Dust Mite Population" - Clinical Allergy, 1986 - Volume 16, pages 41- 47).

The HDM, as its name suggests, inhabits indoor environments, in particular those inhabited by humans or animals. Amounts of microscopic flakes of skin are shed continually by humans or animals, and these flakes fall to the floor, beds and furnishings in a household, and where there is a fabric covered article, the skin flakes will gradually seat within the article. The HDM feeds from these flakes as they decompose, and it will be appreciated where large amounts of flakes are collected, large concentrations of HDM are found. Most commonly infested areas are thus bedrooms and lounges where much human or animal use is made of the furnishings therein.

Research has shown that the effects of living in environments free of HDMs, such as hospitals, where few places are found for the HDM to live and breed, is often beneficial to humans with a propensity to develop respiratory problems such as asthma and other diseases such as rinitis and eczema. It is believed that not the HDM itself, but an allergen or group of allergens called Der.p l , hereinafter referred to as the HDM allergen, associated with the faecal pellets of the mites is a contributing factor if not a major cause of these diseases. It is believed that the HDM allergen causes an allergic reaction, which brings about inflammation of the tissue at the surface of the bronchioles in the lungs of an asthmatic person where the allergen comes to rest, where the inflammation causes breathing difficulties.

The HDM allergens are present in microscopic dust particles, often not visible to the human eye, which are easily disturbed and subsequently made airborne by humans and animals within an infested dwelling, enabling them to be inhaled to the detriment of the inhabitants. The particles may be disturbed by simple actions such as walking on the carpet, reposing in bed or sitting down on a chair or sofa. In consequence, the airborne allergens tend to be at a low level in a room, for example up to a height of approximately one metre.

Many methods are currently available for eliminating the house dust mite, including heat treatment and pesticide spraying of textiles which are susceptible to infestation, but no method specifically relates to both the elimination of the mites and the air quality of the inhabited environment.

It is therefore an object of this invention to alleviate the suffering of humans from asthma and other like diseases by providing a controlled environment in which the amount of house dust mites and their allergens is substantially reduced or they are eliminated all together. The invention also applies to the reduction or elimination of other airborne allergens such as dog and cat allergens and cock roach allergens, and dust particles.

The invention has various aspects.

According to a first aspect of the invention there is provided a method of controlling the air quality of an enclosed environment containing textile furnishings providing breeding grounds for dust mites and/or allergens thereof, wherein the air is replaced with relatively clean air substantially continuously, or as needed, over an operational period, and, at least in a selected part of the enclosed environment, at least one of the following additional measures is effected:

(i) the relative humidity of the air over said operational period is limited to a mean value not exceeding 55%, and/or

(ii) the furnishings are treated for elimination of dust mites and/or allergens thereof and/or (iii) the relatively clean air is introduced into the at least selected part of the environment at the top region thereof and is removed at the lower region thereof.

According to a second aspect of the invention, there is provided a method of controlling the air quality of an enclosed environment containing textile furnishings providing breeding grounds for dust mites and/or allergens thereof, wherein the air is extracted and replaced with relatively clean air substantially continuously, or as needed, over an operational period, and, at least in a part of the enclosed environment, at least one of the following additional measures is effected: (i) a further extraction means is provided for extraction of the air from the lower region of the at least selected part of the environment over the operational period to the atmosphere surrounding the enclosed environment;

(ii) the relative humidity of the air is limited, over the operational period, to a mean value not exceeding 55%

(iii) the furnishings are treated for elimination of dust mites and/or allergens thereof.

When the furnishings are treated they are preferably treated so as to eliminate the mites and also denature the existing allergens.

It is preferable that where additional measures are effected as above is an environment or part thereof which is regularly occupied or occupied for extended periods of time by a sufferer of asthma or respiratory or other condition, for example a bedroom in a house.

The air is preferably changed by a ventilation unit with air propulsion means for propelling air from an air outlet into the said environment or part thereof. The ventilation unit may also be adapted to expel or permit expulsion of the air from the said environment or part thereof to outside the environment or part thereof.

The ventilation unit preferably has more than one air outlet for charging air into different locations within the enclosed environment or part thereof.

It is preferable that where a part of the environment is controlled, one of the air outlets is located to discharge air into the part, and another air outlet is located to discharge air into the remainder of the enclosed environment.

In the case where said ventilation unit is provided with air extraction means, air is preferably extracted from the environment or part thereof, and discharged to the atmosphere outside the enclosed environment or part thereof.

It is further preferable that said air extraction means be located in the enclosed environment or part thereof.

In the case where air is both injected into and extracted from the enclosed environment or part thereof to change the air, the preferred rate of change of air is once per hour.

The ventilation unit is preferably provided with filter means to filter the air from outside the enclosed environment before it is injected into said environment.

The ventilation unit is also preferably provided with heat exchanging means to warm or cool the air from outside the enclosed environment or part thereof such that air injected into the enclosed environment or part thereof has an acceptable value of humidity.

Where the whole environment is controlled, the environment may comprise a part of a larger volume. For example, a room in a house may comprise the environment, in which case there is no additional control on the remainder of the house, or alternatively, such a bedroom may comprise a part of the environment (the whole house) in which case the remainder of the house is also under control. In one specific example, the ventilator unit comprises a unit positioned in a wall on the environment or part thereof to be controlled, and air is pumped into the environment or part thereof through a duct which extends from top to bottom of the environment or part thereof. The incoming cold air is either heated by a heating means and/or is heated by heat exchange with the air which is withdrawn from the environment or part thereof as it is discharged to atmosphere, also by the ventilation unit. The air which is being withdrawn from the environment or part thereof enters the duct at a low level inlet, and is discharged through the wall at a position approximately half way up the duct, whilst the incoming fresh air is passed up the duct from the central region thereof, and is discharged into the environment or part thereof at the top of same. Such a flow arrangement ensures that the low lying air, which contains the majority of the allergen, dust mites and the like, is drawn out of the environment or part thereof and is discharged into the atmosphere. The fresh, clean air is on the other hand injected at the top of the environment or part thereof, and feeds downwards replacing the polluted, removed air.

The invention has advantage over conventional HDM control systems in that air which has been polluted with HDM allergens may be removed and replaced with clean air substantially free from said allergens. In many cases it is not sufficient to simply eliminate the HDM, as HDM allergens would still exist after such an elimination, and still have a detrimental effect on asthma sufferers.

The conditions created by the invention in the environment or part thereof have the further advantage that the humidity level required in certain aspects of the invention inhibits HDM breeding and indeed assists its elimination, as the HDM requires moisture received from air with a mean humidity of greater than 55% to survive. In one aspect of the invention therefore, it is not necessary to treat the furnishings in the enclosed environment to eliminate the HDM, as this is gradually effected by the lack of moisture in the air expelled into the enclosed environment or part thereof. However, in the most preferred embodiments of the invention, both the furnishings within the enclosed environment or part thereof will be treated, and the humidity level of air injected into said environment or part thereof will be controlled, as this will provide the most allergen free conditions most quickly, and henceforth the least discomfort to asthma sufferers and the like.

Also according to the invention there is provided an installation fitted to an enclosed environment for controlling the air quality thereof wherein the environment or a part thereof contains textile furnishings providing breeding grounds for dust mites and/or allergens thereof, including means for replacing the air in said environment substantially continuously, or as needed, over an operational period, and means for effecting in said environment or part thereof, at least one of the following

(i) controlling the relative humidity of the air over said operational period to limit it to a mean value not exceeding 55%, and/or

(ii) treatment of the the furnishings for elimination of dust mites and/or allergens thereof and/or

(iii) extraction of the air in said environment or part thereof over the operational period to the atmosphere surrounding the enclosed environment and/or (iv) providing that the air which is removed from the environment or part thereof is removed at a low level, and that the fresh air is injected into the environment or part thereof at a high level.

Embodiments of the invention will now be described by way of example with reference to the following diagrams, wherein:

Fig. 1 shows a schematic sectional view of a house in which a ventilation system to operate in accordance with the invention has been installed,

Fig. 2 shows the upper portion of the house of Fig. 1 with an alternative ventilation system to operate in accordance with the invention;

Fig. 3 shows another embodiment of the invention;

Fig. 4 shows, to an enlarged scale and in sectional side elevation, the ventilator duct shown in Fig. 3 ;

Fig. 5 shows the duct of Fig. 4 is front elevation; and

Figs. 6, 7 and 8 show alternative arrangements to that shown in Fig. 4.

Although the following description of the invention is limited to the application of the invention within houses, which are the most common environments or 'enclosed areas ' to which the invention may be applied, the invention is not intended to be limited in this way. Indeed, it is foreseeable that any building or environment which contains furnishings or articles which are susceptible to infestation by dust mites would benefit from application of the invention. Examples include warehouses, factories, offices, hotel rooms and the like where dust may accumulate.

According to the embodiment of the invention in Fig. 1, there is provided a house 10 with four rooms, namely a living room 12, a bathroom 14, a kitchen 16, and a bedroom 18. The house has a roof 20 which defines a loft area 22, and two central partitions 24, 26 in which are disposed doors (not shown) to provide entrance to the rooms 14, 18 from a hall area 28, and also to rooms 12, 16 from a hall area 30.

A ventilation unit 32 disposed in loft area 22 is supplied with air from the atmosphere 1 surrounding the house 10 by air intake pipe 34 and expels air through air outlet pipe 36, back to atmosphere. The ventilation unit 32 injects air into the house via outlet pipes 38, 39, and is further provided with an air extraction pipe 40 which removes air from the room 18. It might be noted at this point that the door into room 18 should be made as air tight as possible, for example by having draught excluding seals or strips, and that the door should be spring loaded so that it remains closed unless someone is holding it open.

In the most preferred application of the invention, the ventilation unit 32 injects 25% of air received from air intake pipe 34 into the room 18 and 75% of air received into the hall area 28. In room 18 therefore, air is injected and extracted thus providing a continuous air change exclusively for that room. The air injected into the house 10 by air outlet pipe 39 circulates throughout the entire house, possibly with slight pressurisation of the said house. The room 18 contains a bed 42 with a mattress 44 and a pillow 46 (and possibly other soft furnishings) which are susceptible to infestation by dust mites, and may be considered to have been infested by same.

Preferably, the mattress 44, pillow 46 and any other soft furnishings are first treated by any known method, such as pesticide spraying or heat and steam treatment to destroy any dust mites living therein, and preferably by any one or more of the methods set forth in International Patent Application No. WO96/03870. In particular, the item to be treated is ideally covered enveloped in an air impermeable, heat welded plastic, tarpaulin or like material cover and a probe is inserted within the item containing the dust mites and their allergens. The probe supplies heat internally of the item and subsequently flushes the item with steam, which has the combined effect of killing the dust mites and their allergens and also of urging the resulting detritus outwardly of the item and into the sealed cover which envelops it. The mixture of steam, air, and detritus contained within said cover may optionally be expelled externally of the building in which the item is located or be recirculated through the probe to ensure complete cleansing of said item. It should be pointed out that prior art methods heat and steam the item externally thereof and resulting detritus remains inside said item. This has proven to be ineffective for the permanent removal of dust mites and their allergens.

The cover is ideally manufactured from a material which has a propensity to retain its thermal energy, such as an Aluminium thermal material or a high performance thermal material such as those used in the manufacture of hot air balloons. The improvement resulting from the use of such material lies with the reduction of condensation of the steam internally of the cover, and the maintenance of the high («100°C) temperature at the surface of the item where the majority of the dust mites are killed and their allergens denatured.

Methods currently exist wherein there is simultaneous denaturing of the allergens produced by said dust mites as they are destroyed, but in cases where such methods are not employed, a denaturing process should be undertaken subsequently. Hence the mattress 44 and pillow 46 are rendered substantially free of dust mites and allergens.

However, in many circumstances, such treatment is insufficient to completely alleviate the suffering of asthmatics who may sleep in the bed 42, and additional measures are required to create a tolerable environment.

In this regard, air in the room 18 is continuously changed to remove any remaining allergens in dust particles which may be disturbed by the movement of a human on the bed 42, or by other effects. Although ventilation unit 32 is shown as having an outlet pipe 38 and an extraction pipe 40 in only the bedroom 18 of the house 10, it is foreseeable that additional air outlet and extraction pipes may be attached to said ventilation unit 40 in order that air may be changed in other rooms within the house 10. Alternatively, to provide an overall flow of air through the house and avoid potential pressurisation problems created by injection of air through air outlet pipe 39, a separate air extraction unit (not shown) may be provided within the loft area 22 in order to extract air from a low level in the house via an air extraction pipe (also not shown) similar to air extraction pipe 40. In addition to or instead of extraction pipe 40, there may also be provided a simple, commonly known extraction fan ventilation unit (not shown in this embodiment) in the external wall 19 of the room 18 to more effectively extract the air from the said room. Such a unit may have a variable speed, silent running motor of known type. In an embodiment such as that shown in Fig. 3 , where only an extraction fan unit is provided in wall 19, the rest of the house is not otherwise conditioned, the need to seal off the room 18 with the sealing strips and the automatic door closing, as much as possible may be of more significance. The ventilation unit is in such case provided to draw air in from the atmosphere 1 , and either to discharge it back or allow it to discharge back into the atmosphere 1 , the flows of air in opposite directions performing heat exchange as they contra flow through the unit. The incoming air receives heat and the outgoing air gives it up. The unit may have a filter to filter out undesirable particles and may have a heater or cooler to add or remove heat to or from incoming air in order to control the temperature and hence relative humidity of the air in the room 18. There may be a sensor and feedback system to provide automatic control of the humidity of the air in the room 18. The sensor may be adapted to sense not only relative humidity, but also presence of gases, such as carbon dioxide. It is known that carbon dioxide builds up in bedrooms during the night when a person is sleeping, and such build up can bring on an asthma attack. The sensor can be arranged to sense this and instruct the control system to take corrective action. This can be in addition to the other controls, and the concept can be extended to the build up of other undesirable gases. Furthermore, although it is preferred to inject the fresh air at the top of the room and extract stale air which is more likely to have airborne allergen (as shown in Fig. 1), an alternate disposition of the outlet and extraction pipes 38, 40 may be employed wherein air is extracted at the top of the room 18 and injected at the floor of the said room by the ventilation unit 32.

In the present embodiment however air is injected through the outlet pipe 38 at the top of the room, and is generally diffused into the room 18 by diffuser means (not shown) . Air from the atmosphere 1 may also be treated in the ventilation unit 32 either by using heat exchange means to warm the air, and hence reduce the humidity thereof, or by specifically filtering to remove any unwanted particles from said atmospheric air, or both treatments may be applied. In the case where the temperature of the air is altered by the ventilation unit 32, a feedback system (not shown) may also be employed which monitors the relative humidity of the air being injected into the room 18 and automatically adjusts the amount of heat transferred to the air by the heat exchange means in the ventilation unit 32. Steady humidity levels of the injected air can thus be maintained.

The advantage of heating the air, and thus reducing the humidity thereof, lies in the inability of dust mites to breed below certain levels of air humidity-the generally accepted level being 55%. A continuously changing air supply with this level of humidity or lower therefore not only removes irritant dust particles which may contain harmful allergens from a room, but also prevents re- infestation of dust mites after furnishings in the room have been treated as hereinbefore described. In a further embodiment of the invention, the air intake for the ventilation unit 32 may be inside the loft 22 of the house 10. In most cases, the heating provided by sunlight on the roof 20 of the house, and the ambient temperature of the air therein due to thermal convection will be sufficient to ensure that the humidity level of that air is below 55%, and may thus be expelled into the room 18.

Referring now to Figure 2, a ventilation unit 50 is disposed within the loft area 22, and has connected to it air outlet pipes 51, 52 which inject air from the loft area 22 into the room 18 and into the hall area 28. As in previous embodiments, 25% of the air intake of the ventilation unit 50 is injected into the room 18, and the remaining 75% of the air intake is injected into the hall area 28. Also as in previous embodiments of the invention, to provide an overall flow of air through the house and avoid potential pressurisation problems created by injection of air through air outlet pipes 51 , 52 a separate air extraction unit (not shown) may be provided within the loft area 22 in order to extract air from a low level in the house, and especially the room 18 via an air extraction pipe (also not shown) .

The effect of the ventilation unit 50 in this embodiment of the invention is to slightly pressurise the house such that air is expelled therefrom through natural escape points (not shown), such as cavities, recesses, windows doors and the like. Air intake for the ventilation unit 50 is in the loft 22 where the ambient temperature is in most cases sufficient to ensure that the relative humidity of the air expelled inside the house 10 is below 55%, and dust particles in the air within the house 10 which may contain dust mite allergens are expelled as the air is forced through said natural escape points to the external atmosphere 1. Air injection into room 18 and area 28, air escape, air movement in the hall area 28, and air movement across the central partition 26 are indicated generally by arrows 52a, b, c, d, e respectively.

A possible enhancement in the operation of the invention may be brought about by utilising a specifically adapted vacuum cleaner (not shown) on the carpets and other textiles in the house. Many current vacuum cleaners make use of a suction pump to provide the necessary force to lift particulate matter from carpets, curtains and other similar furnishings. Air laden with said particulate matter is subsequently blown into a fabric or paper bag which allows air to pass through and retains said particulate matter inside the bag. Often, dust particles are of such size that it is possible for more minute particles to escape from the bag with the air and return to the atmosphere of the room in which the vacuum cleaner is being utilised. More specifically, dust mite allergens may also be returned to the atmosphere in this manner.

Common vacuum cleaners may be easily adapted for use with the present invention by attaching one end of a pipe to the suction outlet of the pump of the vacuum cleaner, and the other end of said pipe either to an outlet to the atmosphere, or to the end of the air extraction pipe 40 as shown in Figure 1. In this manner, dust mite allergens may be safely removed from the room 18 during any vacuum cleaning operations.

Figs 3 , 4 and 5 illustrate another embodiment of the invention in which a ventilation unit 100 is mounted in or on the wall 19 of the house 10. The unit is mounted approximately half way up the part of the wall 19 which bounds the bedroom 18, and inside the wall (in the bedroom or perhaps in the wall cavity) is a duct 102 which extends from top to bottom of the bedroom 18. The duct 102 has an outlet 104 at the top and an inlet 106 at the bottom. The outlet and inlet may be covered by a grill as shown.

The duct interior communicates with the unit 100 but is split centrally by means of a partition 108 to ensure that the flows of air through the duct 102 are as required and as described herein. The partition is located where the duct 102 communicates with the unit 100 and the arrangement is that the unit 100 pumps air from the atmosphere 1 through the unit 100 and into the duct 102 above the partition 108, so that this fresh air travels up the duct and is injected into the room 18 at the top thereof as shown by arrows 110.

On the other hand, the air at low level in the room 18 is drawn by the unit 100 into the inlet 106, as shown by arrows 112 and through the lower half of the duct 102 to the unit 100, from whence it is discharged into the atmosphere 1. As the warmer air which being discharged passes through the unit 100, it gives up some of its heat by heat exchange to the fresh incoming air to pre-heat same. The unit 100 may additionally include a heater to further heat the air.

In this embodiment, which can be used on its own or in conjunction with any other embodiment, the advantage is that the lower air in room 18, which tends to contain more allergen than the higher air, due to the fact that although dust mites and allergen are raised in the room by human movements, the dust mites and allergen are heavier than air and tend to gravitate back to the lower levels, is directly removed from the room and as the process of air changing continues, so the level of dust mite and allergen, and indeed other airborne particles, progressively reduces.

In the alternative embodiment shown in Fig. 6, there is a fan 100 in the wall 19, but the heat exchanger 100A is a separate unit located in the duct 102. It performs the same function of transferring heat from the air which is being discharged to atmosphere to the fresh air which is being injected into the room.

The embodiment of Fig. 7 has no heat exchanger, and no duct 102. There is an injection fan 200 at the top of the wall which injects fresh air into the top of the room directly, and a fan 202 at the bottom of the wall which draws the warm stale air from the room at the low level.

In the arrangement shown in Fig. 8, heat exchange takes place as the fresh air 110, drawn in by a fan 204 at the lower end of wall 19, passes up throughout the height of the duct 102. This air is discharged into the room at the top level through outlet 104. The stale air is drawn into a heat exchange tube 206 in the duct 102, which extends in a sinuous or other manner, from the bottom of the duct 102 to the top thereof, where it is connected to a discharge fan 208. Fan 208 discharges the stale air 112 to the atmosphere, as shown.

As will be understood, there are many ways of injecting fresh air and discharging stale air, and in each case one or two fans can be used.

It is to be pointed out that any feature or aspect of any embodiment of this invention or any method or apparatus as described herein capable of being used in combination with any other such feature or aspect, is considered as being described in such combination, in that the applicant wishes to reserve the right subsequently to claim such combination in the claims of this application.

Claims

CLAIMS.

1. A method of controlling the air quality of an enclosed environment containing textile furnishings providing breeding grounds for dust mites and/or allergens thereof, wherein the air is replaced with relatively clean air substantially continuously, or as needed, over an operational period, and, at least in a selected part of the enclosed environment, at least one of the following additional measures is effected:

2. A method of controlling the air quality of an enclosed environment containing textile furnishings providing breeding grounds for dust mites and/or allergens thereof, wherein the air is extracted and replaced with relatively clean air substantially continuously, or as needed, over an operational period, and, at least in a part of the enclosed environment, at least one of the following additional measures is effected:

(i) a further extraction means is provided for extraction of the air from the lower region of the environment or part thereof over the operational period to the atmosphere surrounding the enclosed environment;

(ii) the relative humidity of the air is limited, over the operational period, to a mean value not exceeding 55% (iii) the furnishings are treated for elimination of dust mites and/or allergens thereof.

3. A method according to claim 1 or 2, wherein when the furnishings are treated they are preferably treated so as to eliminate the mites and also denature the existing allergens.

4. A method according to claim 1, 2 or 3, said environment or part thereof is one which is regularly occupied or occupied for extended periods of time by a sufferer of asthma or respiratory or other condition, such as a bedroom in a house.

5. A method according to any preceding claim, wherein the air is preferably changed by a ventilation unit with air propulsion means for propelling air from an air outlet into the said environment or part thereof.

6. A method according to claim 5, wherein the ventilation unit is adapted to expel or permit expulsion of the air from the said environment or part thereof to outside the environment or part thereof.

7. A method according to claim 5 or 6, wherein the ventilation unit charges fresh air from the surrounding atmosphere into the top of the environment through the top half of a duct which extends from top to bottom in the environment or part thereof, and withdraws air from the bottom of the environment through the lower half of the duct and discharges it into the atmosphere.

8. A method according to claim 7 wherein the fresh air undergoes heat exchange with the air which is withdrawn from the environment or part thereof for the pre-heating of the fresh air.

9. The method according to any of claims 5 to 8, including a further ventilation unit having more than one air outlet for charging air into different locations within the enclosed environment or part thereof.

10. The method according to claim 9, wherein a part of the environment is controlled, and one of the air outlets is located to discharge air into the part, and another air outlet is located to discharge air into the remainder of the enclosed environment.

11. A method according to claim 9 or 10, wherein the further ventilation units extracts air from the environment or part thereof, and discharges it to the atmosphere outside the enclosed environment or part thereof.

12. A method according to claim 9, 10 or 11, wherein the enclosed environment is a domestic dwelling having a roof space, and the further ventilation unit is contained in the roof space.

13. The method according to claim 5 or any preceding claim when dependent upon claim 5, wherein the ventilation unit and/or the further ventilation unit is provided with filter means to filter the air from outside the enclosed environment or part thereof before it is injected thereinto.

14. The method according to claim 9 or any preceding claim when dependent upon claim 9, wherein the further ventilation unit is provided with heat exchanging means to warm or cool the air from outside the enclosed environment or part thereof such that air injected into the enclosed environment or part thereof has an acceptable value of humidity.

15. The method according to any preceding claim, wherein a part of the environment is controlled, and said part is a room in a building.

16. An installation fitted to an enclosed environment for controlling the air quality thereof wherein the environment or a part thereof contains textile furnishings providing breeding grounds for dust mites and/or allergens thereof, including means for replacing the air in said environment or part thereof substantially continuously, or as needed, over an operational period, and means for effecting in said environment or part thereof, at least one of the following

(v) treatment of the furnishings for elimination of dust mites and/or allergens thereof and/or (vi) extraction of the air in said environment or part thereof over the operational period to the atmosphere surrounding the enclosed environment (vii) providing that the air is replaced by being injected into the environment or part thereof at a high level, and removed by being withdrawn at a low level.