GB2299762A - Respiratory mask - Google Patents

Abstract

A mask for protecting the respiratory system comprises a full face mask 1 of open or closed cell foam with curved eye pieces or a visor and integral bands 5a, 5b for wrapping around the head, the bands having respective hook and loop pads for overlapping and fastening together. The mask includes a face seal (11) and one-way exhalation valves 17a,(17b) located in the nose and mouth area and may include a filter assembly 19 extending along at least one side to provide a passage for air to the mask interior. The assembly houses a filter 27 which may be formed from a series of filter regions arranged so that different particulates and/or toxic gases are sequentially removed from the air passing through the filter.

Description

MASK This invention relates primarily to a mask suitable for use in hazardous environments to protect the respiratory system.

A person having to escape from a hazardous environment may be at risk of poisoning, which could be life threatening, due to inhalation of toxic gases or vapours, smoke or other gas-borne particles. There are several known methods of protecting the respiratory system in hazardous situations such as, for example. in the event of a fire or chemical spillage.

A first method is to use a protective plastics hood w ith an elasticated opening at the bottom, which is placed over the head and supplied with air from a suitable source such as an air or oxygen cylinder. A problem with this method is that only a limited supply of air can be easily carried by an individual. Furthermore, there is a build-up of carbon dioxide in the hood, from exhalation gases of the wearer. A half mask can be used with the hood to avoid carbon dioxide build up but this can be difficult to put on in an emergency. However a problem with using a half mask is that if the user is wearing a helmet it must be removed before putting on the hood. Additionally, if glasses, safety goggles or the like are worn, they are likely to be displaced during the donning process.

A second method is to use an oxygen generation device which is held in the mouth.

This method avoids time wasted in removing a helmet, and there is no build up of carbon dioxide since air is exhaled into the environment.

A third method uses a different approach. In this method, instead of using an air or oxygen source which must be carried by the user, a filter unit is employed, in conjunction with a hood, which filters air passing into the mask from the external environment. This method cannot be used in situations where the atmosphere contains little or no oxygen. Another difficulty is that the apparatus can be bulky to carry and the user must remove any helmet being worn before putting on the hood, again wasting valuable time in an emergency situation.

Another method employed is to use breathing apparatus comprising a full face mask used in conjunction with a limited air or oxygen supply from a cylinder.

It would be desirable to provide a mask for protecting the respiratory system of individuals needing to escape from hazardous environments which can be utilised easily and quickly and which is lightweight, compact and easy to carry upon one's person.

The present invention provides a protective breathing mask which can be simply wrapped around and secured to the head using fastening means which are fastened without requiring fine alignment. The mask may include at least one relatively wide band (or strap) extending from one or both sides of the mask which can be completely wrapped around the head, preferably at the level of the ears. The band has fastening means and is wrapped around the head and overlaps or is overlapped by (as appropriate) a part of the mask (or another band) having complementary fastening means. The fastening means are carried on adjacent facing surfaces of the band and the mask (or the other band) at the overlap and may be readily fastened, by bringing the opposed surfaces into contact, without the need for accurate alignment, to secure the mask to the head.

Preferably the fastening means are respective hook and loop fastening pads (e.g.

Velcro which are quickly and easily adjustable, because there is no need for careful alignment, to fit any size of head.

Preferably the band is sufficiently wide to cover the ears of a user to provide protection for the ears.

In this way the mask can be simply wrapped around and secured to the head of any user because the band can be simply connected over a wide range of lengths. There is no need for the user to remove a helmet or glasses to put on the mask in an emergency since the mask can be wrapped around a helmet or glasses. Thus the mask can be put on in seconds.

The mask may have curved eye pieces made from a protective transparent safety material or may have a single eyepiece.

Preferably the mask is made from a lightweight material so that it can be easily carried around by an individual when not in use. In the preferred embodiment the material is a flexible closed cell or partially closed cell foam such as polyethylene foam which can be formed into a shape which is flexible and conforms with the face whilst providing a breathing space between the mask and the face. The mask can thus be folded up and conveniently stored when not in use.

The mask may have at least one one-way exhalation valve so that exhaled air is released from the mask without allowing external pollutants to enter into the mask.

The mask is preferably formed from a fire and chemical resistant material such as a closed cell or partially closed cell foam. Alternatively, the mask itself is formed from silicone foam which is fire and chemical resistant. In a further alternative the mask could be formed from an open cell foam of lesser specification suitably sealed in a fire retardant and chemical resistant material.

Preferably the mask has one or more air inlet passages for connecting an air or oxygen source. The air passage(s) can connect the air or oxygen source to the eye areas within the interior of the mask from where the air or oxygen flows into the nose/mouth area, preferably via non-return valves.

Altenatively. or in addition, the mask has a filter assembly on one or both sides of the mask. The filter assembly includes a filter housing, in communication with the external environment, which receives a filter unit such as a cartridge or which houses a permanent filter. An air passage extends from the filter housing to the eye areas at the interior of the mask. In one embodiment the air passage is formed from a mounting for a one-way valve which may be moulded into the material of the mask.

Air is drawn into the mask from the environment through the filter and through the valve in response to the demand by inhalations of the user. Thus filtered air can be used to automatically supplement air from the air source or to supply all of the air to the user if the air source runs out or if the hazard does not warrant the use of an air source.

Optionally, the filter is in the form of a unit or 'cartridge' which can be removed and replaced. This filter may be fitted in the filter assembly with its end exposed directly to the atmosphere.

According to another aspect, the present invention provides a protective mask having a filter assembly which is integral with the mask.

According to yet another aspect, the present invention provides a protective mask having a filter assembly at a side of the mask, the filter assembly comprising a filter housing in communication with the exterior of the mask for receiving air from the environment, wherein the filter housing, in use, houses a filter which provides a passage for air received from the environment and filters the air passing through it.

The filter housing is also in communication with the interior of the mask to provide filtered air from the filter into the interior of the mask. Air is drawn from the environment through the filter assembly into the mask in response to the inhalations of the wearer.

Optionally, the filter assembly is adapted for use with a filter in the form of a removable unit or'cartridge'.

Preferably the mask is a full face mask with an integral half mask and/or seal.

According to another aspect the present invention provides a protective mask formed from open cell foam, partially closed cell foam or closed cell foam preferably of polyethylene or silicone.

Preferably the mask is formed from partially closed cell foam which is fire retardant and chemical resistant. Alternatively, or if open cell foam is used, the foam is suitably sealed in a fire retardant and chemical resistant material.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a side view of a mask forming a first embodiment of the present invention shown in use; Figure 2 is a cross section of the mask of Figure 1 shown in use; Figure 3 is a plan view of the inside of the mask of Figure 1 shown opened out; Figure 4 is a side view from above of the mask as shown in Figure 3; Figure 5 is an end view of the mask as shown in Figure 3, Figures 6a and 6b are respectively a plan view and a side view of a filter unit for use with the mask of Figure 1; Figure 7 is a side view of a mask forming a second embodiment of the present invention. shown in use: Figure 8 is a cross-section of the mask of Figure 7 shown in use, and Figure 9 corresponds to the view of Figure 7 shown partly cut away to reveal the filter assembly.

Figures 1 to 6 show a mask forming a first embodiment of the present invention.

The full face mask 1 has a front portion 3 for covering and protecting the face of a user. Extending from the sides of the mask are integral wide bands 5a, Sb which enable the mask to be simply wrapped completely around the head of the user at the level of the ears. The bands 5a, Sb are sufficiently wide to completely cover, and therefore protect, the ears of the wearer. The bands Sa, 5b are overlapped at the back of the head and the mask is tightly secured to the head by respective hook and loop (e.g. Velcro3) fastening pads 7a, 7b provided on opposing surfaces of the bands 5a, 5b near to their respective ends. The fastening pads 7a, 7b extend along a sufficient length of each band to enable the overlap to be adjusted to fit different sized heads.

The front portion 3 of the mask has a pair of curved eye pieces 9a, 9b made of a transparent, impact resistant, protective material. Such materials are known and used, for example, in safety goggles.

It will be appreciated that alternative designs of masks in accordance with the present invention could have a single eye piece.

The mask 1 is formed, as described below, from a partially closed cell polyethylene foam which is impenetrable to external gases. This material is particularly suitable because it is inter alia lightweight and flexible. In addition, the mask is coated on its external surface with a flame retardant and/or chemical resistant material to provide protection from these hazards.

The skilled person will appreciate that it would be possible to use an open cell foam sealingly coated with a flame retardant and/or chemical resistant material.

Alternatively a coating would not be necessary if the partially closed cell foam was of a specification having fire and chemical resistant properties.

At the front portion 3 on the interior of the mask 1 is an integral face seal 11 (shown in cross section in Figure 2) to seal the mask against the face. Such a seal is known and used in conventional breathing apparatus.

The seal 11 is shaped to conform with the face so that, in use, it provides a tight seal between the mask and the user's face at the seal. This seal prevents the ingress of polluted air from the environment into the mask.

The upper part of the nose and mouth cup 14 has on each side a one-way valve 14a and 14b respectively through which air can pass from the interior eye area of the mask into nose and mouth cup 14 for breathing. It will be understood that just one valve could be used.

On both sides, at the bottom of the front portion 3 of the mask are respective air inlet passages 12a and 12b which can be connected to respective air supply hoses 15a and 15b from an air source (not shown). Each air passage extends upwardly from the valve to just below the level of the eyepieces 9a, 9b. The air source provides a continuous air flow at a specific rate.

It will be appreciated that the mask could have a single connection point for entry of air from an air source with two moulded channels extending up to the level of the eyepieces of the mask.

Two one-way exhalation valves 17a and 17b extend from inside the nose and mouth cup 14 to the outside of the mask and are situated on either side of the mask, just below the mouth area. Each exhalation valve I 7a and 1 7b is opened by the force of the flow of air exhaled by the wearer whilst any inflow of environmental gases is prevented.

It will be understood that just one one-way exhalation valve could be used.

The mask according to the first embodiment additionally has a filter assembly 19 on each side of the mask so that filtered air can be provided to the mask from the environment when or if an air supply runs out, is not available or is not warranted.

The filter assembly 19 includes a filter housing 21 incorporated within the mask which is directly exposed to the external environment by way of an air inlet 23 and extends along the full length of the side of the mask up to the seal 11. A one-way valve 29 is mounted in an air passage which extends from the filter housing 21 through the seal 11 to the eye area of the interior of the mask. The filter assembly 19 provides a passage for air from the environment to the interior of the mask. Adjacent the air inlet 23 is a fibreglass pre-filter (not shown) which prevents large particles from entering the filter assembly. Each filter housing 21, as described below, in use, houses a filter 27 of a filter unit 26 in the form of a 'cartridge'. The filter 27 removes particulates and toxins from air drawn through it.

The filter unit 26, shown in detail in figures 5 and 6 comprises a generally rectangular foam base 28 and a filter 27 projecting from the base 28 shaped to be snugly received in the filter housing 21. The filter 27 may comprise various substances for removing toxins and particulates from the air passing through it, for example, open cell foam impregnated with appropriate substances for removing the toxins and particulates.

Such filters are known, an example being a catalytic converter which removes carbon monoxide from the air by converting it to carbon dioxide.

The filter 27 is formed, in this embodiment, from a graduated series of filter regions of different materials arranged so that different particulates and toxins are sequentially removed from the air passing through the filter.

An advantage of the filter extending along the relatively long length of the side of the mask and thus providing a relatively long passage for filtering air is that filtration is more efficient than for a filter providing a shorter passage for air.

It will be appreciated that the materials used in the filter can be changed according to the requirements of the environment.

The filter unit 26 is secured within the filter assembly of the mask by inserting the filter 27 in the filter housing 21 and, using, for example, double sided sticky tape 33, adhering the filter carrying surface of the base 28 of the filter unit 26 bounding the filter to the facing surface of the side of the mask surrounding the filter housing 21.

The filter unit 26 may therefore be removed from the filter housing 21 by tearing the unit from the mask. Since the filter unit is in the form of a 'cartridge' it can be replaced once its lifetime has expired or changed for a different filter for use in a different environment.

Figures 7 to 9 show a mask forming a second embodiment of the present invention in which parts corresponding to those in the first embodiment have been given like reference numerals.

As in the first embodiment, the full face mask 1 of Figures 7 to 9 has a front portion 3 and integral wide bands Sa, 5b one extending from either side of the front portion 3 so that the mask can be readily wrapped around the head of the user at the level of the ears. The bands 5a, 5b have complementary hook and loop fastening pads 7a, 7b as in the first embodiment.

The front portion 3 of the mask has a pair of eye pieces 9a, 9b each in the form of a visor which is moulded into the mask. East visor comprises a front. upper and side portion which are positioned at appropriate angles with respect to each other to give good visibility. The visor is made of a suitable transparent, impact resistant and protective material.

In this embodiment the mask is formed of partially closed cell silicone foam which has fire and chemical resistant properties. The external surface of the mask is coated with a thin silicone material or "skin" which facilitates elasticity whilst providing tear resistance.

As with the partially closed cell polyethylene foam used in the first embodiment, the partially closed cell silicone foam is lightweight and flexible and can be readily moulded into the required shape.

As can be seen from Figure 8, the mask 1 is formed in two pieces. The inner piece is a full mask with an integral face seal 11 for sealing the mask against the face in use. The face seal 11 is shaped to conform to the faces of the widest possible range of users. The outer piece includes the full front portion 3 and bands 5a and Sb. The eye pieces 9a and 9b are moulded into the outer piece.

As with the first embodiment, the seal has a nose and mouth cup 14 which forms a complete and fixed unit. On the upper part of the nose and mouth cup 14 is a oneway valve 14a, 14b through which air can pass from the interior eye area of the mask into the nose and mouth cup for breathing. In addition, on either side at the lower part of the nose and mouth cup is an outlet which leads to one-way exhalation valves 17a, 17b respectively on the exterior the mask 1. The exhalation valves are similar to those described in relation to the first embodiment.

The mask further has air inlet passages 12a, 12b connected to an air supply hose of an air source (not shown). However, unlike the air inlet passages 12a, 12b of the first embodiment, air is not conveyed directly into the eye area of the mask but is conveyed via the filter system as described below.

The mask according to the second embodiment has a filter assembly 19 on each side of the mask so that filtered air can be provided to the mask from the environment.

The filter assembly in this embodiment is a fixed and integral assembly. Referring to Figure 9, the assembly comprises a housing 21 which is exposed to the external environment by way of inlet 23. The housing 21 has a generally rectangular transverse cross-section, corresponding to the area of the inlet, and extends along the side of the head, across the ears to the edge of the eye pieces. The filter housing 21 thus provides a passage for air from the environment to the interior of the mask. It will be noted that because the eye pieces are moulded or bonded into the outer piece of the mask, the air passage from the filter system into the interior of the mask is not obstructed.

The filter housing 21 houses a filter 27 comprising a number of filter segments 27v, 27w, 27x, 27y and 27z. Each filter segment has a cross-section, perpendicular to the direction of air flow, corresponding to the transverse cross-section of the filter housing so that air flowing through the filter 27 must pass through the filter material.

The filter segments 27v, 27w, 27x, 27y and 27z are spaced apart from each other so that there are air gaps between them.

The filter segment 27v closest to the air inlet 23 is in abutment with the inlet 23 and comprises a pre-filter material such as fibreglass which prevents any large particles passing into the filter and causing a blockage. The prefilter also assists with heat dissipation and protects the filter from any ambient heat. Mounted in the gap between the pre-filter 27v and the next filter segment 27w is a one-way valve (not shown) which prevents the backflow of air out of the mask through the inlet 23.

The next filter segment 27w in from the inlet is a carbon filter. as is the last filter segment 27z. In between the two carbon filter segments are two filter segments 27x.

27y comprising HOPCOLITE (trade mark) sintered to carbon material. The sintered HOPCOLITE (trade mark) filter acts as a catalytic converter, converting carbon monoxide to carbon dioxide. It will be noted that since the catalytic converter reaction is exothermic, the filter segments 27x and 27y tend to wann up in use.

The advantage of having a series of filter segments along the path of air flow through the filter unit, with an air gap in between each of the filter segments, is that the air flow created is non-laminar which improves the efficiency of filtration. Furthermore, air flow is less likely to be impeded by a blockage in a part of the cross-sectional area of one of the filter segments than would be caused if the air flow were laminar. If such a blockage were to occur in one of the filter segments of this embodiment, the full cross-sectional area of the other filter segments could still be utilised since the air gaps allow the air flow to take a labyrinthine path through the filter segments avoiding any blockages.

It will be appreciated that other filter configurations are possible and different filter materials may be used depending upon the circumstances for which the mask is to be used.

In addition to the filter assembly filtering air from the environment, the air flow from an air supply is also passed through the filter. Thus, the air inlet passages 12a and 12b extend from the air supply hose 15 of the air source through the mask material to the filter. Each air inlet passage passes around the base of the mask along the side and back to just behind the pre-filter segment 27v (as shown in Fig. 9) and is then diverted back into the filter housing in the direction of the eye area of the interior of the mask. The air from the air supply is thus caused to flow through the filter 27 into the interior of the mask.

One advantage of diverting the air from the air supply through the filters is that it has a cooling effect which is particularly important for the catalytic convertor filter segments 27x. 27y which tend to warm up. It may also help to improve air flow into the mask from the environment.

The air gaps between the filter segments also help to disperse air which is heated as a result of the exothermic reaction within the catalytic converter filter segments.

The mask may be manufactured using a number of methods of which the following are examples: A first method is to cut out a blank for the main part of the mask in the general outline of the mask from a sheet of foam and to separately cut out a blank for the seal area from the same foam. The seal part is then welded to the main part and the seal is thermo formed to shape it into the desired face shape. The various valves (air receiver/exhalation valve) are then incorporated within the mask by hand drilling and any outer material and eye pieces are welded in place using high frequency welding.

An alternative method is to mould the mask in one piece by forming the foam material within a suitable mould. The apertures for the eye pieces and the valves, and the filter housing are integrated within the mould and the eye pieces and valves are then welded in place using high frequency welding. Mountings for the valves could also be moulded integrally with the mask.

This method is simpler than the first method because it requires less finishing but development costs to produce the mould are naturally higher. However, once the mould has been developed it would be possible to form masks of different foam materials.

A further method, particularly suitable for forming a mask according to the second embodiment is to mould the rnask in tWO pieces. an inner piece and an outer piece.

The foam material could be formed in the moulds, which would incorporate the air supply hoses and filter housing etc. and the two pieces subsequently sealed together.

The mask 1 of both the first and second embodiments is used as follows. The air inlet passages 12a and 12b of the mask 1 are first linked to an air or oxygen source containing a finite quantity of air which can be automatically supplied, at a specific rate, when the mask is removed from its container. The user then places the nose and mouth cup over the nose and mouth area and the mask is tightly wrapped around the head at the level of the ears and is firmly secured in place using the hook and loop fastening pads. As the mask is wrapped first around the face, the shape and material of the seal is such that the foam 'closes' in towards the face forming a tight seal.

Significantly, because of the tendency of the material to close in towards the user's face, the same size and shape of seal can be used to fit 2 to 98S; of the population.

It will be particularly noted that in both the first and second embodiments the shape of the seal and the use of a nose piece between the eye pieces prevents the mask from moving away from face and instead may help to seal the mask. Additionally the seal is soft and pliant and so deflects away from the arms of glasses or anything else being worn beneath it. Thus, the mask can be wrapped around the head without the need to remove glasses or a helmet.

Air from the air source is carried up through the passages 12, as shown by arrow A, into the respective interior eye areas of the mask. In the second embodiment the air passes to the eye area via the filter systems. At the eye area the air from the source flows around the eyepieces 9a and 9b and then down through the one-way valves 14a and 14b into the mouth and nose cup 14. The flow of air around the eyepieces 9a and 9b helps to prevent them from becoming misted.

The wearer inhales the air in the mouth and nose cup 14 and the exhaled air passes out of the mask. as shown by arrow C. through the exhalation valves 17a and 17b.

Whilst the air source is supplying air and the wearer is breathing normally, no air is drawn into the mask through the filter assemblies 19a and 19b. The wearer's demand is met solely by the air source. However, in the event that the wearer has a greater demand than the source can supply, the exertions of the wearer's inhalations will cause air to be drawn into the filter assemblies, at each side of the mask, from the environment. The air drawn in will pass directly into the filter assemblies through inlets 23a and 23b. It will be noted that the length X of the end of the band Sb is greater than the corresponding length Y of the end of the band Sa so that neither of the inlets 23a and 23b to the filters are covered, even when the mask is fastened on a very small head.

The air passes through each filter 27 which removes toxic gases, smoke particles etc.

and the filtered air is then drawn along through one-way valves 29 to the eye pieces at the front interior of the mask. The filtered air can then pass into the nose and mouth cup 14 through the valves 14a and 14b. Thus, as shown by arrow B, air is drawn into the filter assembly 21 into the front interior of the mask in response to the demand of the user.

Accordingly, in the described embodiments filtered air can be used to automatically supplement air from the air source or to supply all of the air to the user. This is particularly useful when only a limited air source is available to the user in an emergency situation. The user can rely on the air source during a short time whilst escaping from or passing through a hazardous environment in which the air is of poor quality e.g. with low oxygen content, and cannot be breathed. Once in a less hazardous environment the filtered air can be breathed.

The ability to supplement the air source with filtered air from the environment therefore provides the wearer with additional time to escape from a hazardous environment for a given size of air supply. Accordingly. the mask of the described embodiments can be expected to provide an increased escape time compared with the prior art for a given air cylinder size.

A particular advantage of the described filter assemblies is that because the filters are located at the sides of the mask, the air has to pass through the whole length of the filter in order to reach the eye pieces at the front of the mask. This ensures that the air is filtered as fully as possible before it is breathed. In addition the filters' location on the sides of the mask provides a degree of protection for the ears.

It will be understood by the skilled person that the mask could be provided without the filter assemblies if the mask is to be used, like conventional breathing apparatus, with a sufficiently large air supply for the time to be spent in the hazardous environment. The mask would be more comfortable, and less cumbersome to wear than conventional breathing apparatus in view of the lightweight, flexible material and because it can be put on by simply wrapping it around the head and securing it at the back. It can thus be put on more quickly (in a matter of seconds) which can save valuable time in an emergency situation.

It will also be appreciated that for some uses for example, where air from the environment contains sufficient oxygen, the mask may be provided without the air receiver so that all the air is supplied to the wearer via the filters. The mask would still have the advantages of the filter assembly as well as being lightweight, compact and easy to use by simply wrapping it completely around the head without the need to first remove a helmet or glasses being worn.

The described masks according to the invention are made from a lightweight foam material but the skilled person will appreciate that other similar materials may be used. However the advantage of using a foam material, and in particular closed cell foam, is that it can be readily manufactured using known techniques, and is also comfortable to wear. In addition the mask can be shaped to provide a degree of protection to the users head, the foam material deflecting external obstacles which the wearer may bump into when trying to escape from a hazardous environment with poor visibility.

The skilled person will appreciate that plastics or rubber foams as well as polyurethane/polyester and silicone based foams can also be used. Silicone and other types of foam may be made lighter in colour and consequently nicer to use than a dark polyurethane foam. Additionally, in the second embodiment the silicone foam does not need to be coated with a fire or chemical resistant material since it has chemical and fire resistant properties.

The described mask provides all round protection which can be used in different environments, in all weathers and climates.

It will be understood that various modifications may be made to the described embodiment and it is intended to include all such modifications and variations as fall within the scope of the accompanying claims.

For example, the filter arrangement of the second embodiment could be used in cartridge form or the arrangement of the first embodiment could be in permanent form. A single wide strap having a Velcro pad could be used and fastened to the side of the mask having a complementary Velcro pad. The one-way valve could be of any suitable construction.

A filter assembly in accordance with the invention and as illustrated by the embodiments could be incorporated within a half mask as well as a full face mask.

The mask has many applications and could be adapted to conform to the standards required for the application. For instance, the mask could be used in aircraft if designed to confonn with CAA standards. Thus the mask can be used in anv circumstances where need to escape from toxic environments.

Claims (17)

1. A mask for protecting the respiratory system of the wearer, which can be wrapped around and secured to the head of the wearer using fastening means which are fastened without requiring fine alignment.

2. A maik as claimed in claiim 1, in which the mask is a full face mask.

3. A mask as claimed in claim 1 or claim 2, having at least one band extending from one side of the mask, the band carrying on its inner surface at least one hook or loop fastening pad, and, in use, overlapping the other side of the mask, or another band extending from the other side of the mask, carrying on its outer surface a complementary hook or loop fastening pad.

4. A mask as claimed in any preceding claim, in which the sides of the mask protect the ears of the wearer.

5. A mask as claimed in any preceding claim, the substantial parts of which are formed from a foam material.

6. A mask as claimed in claim 5, in which the foam is an open cell foam.

7. A mask as claimed in claim 5, in which the foam is a closed cell foam.

8. A mask as claimed in claim 7, in which the closed cell foam comprises polyethylene closed cell foam or silicone closed cell foam.

9. A mask as claimed in any one of claims S to 8, in which the mask is a full face mask.

10. A mask as claimed in any one of claims 5 to 9, in which the mask incorporates an integral face seal formed of the same foam material.

11. A mslrk as claimed in any one of claims 5 to 10, in which the mask incorporates a suitably shaped nose-piece.

12. A mask as claimed in any preceding claim, having a filter assembly extending along at least one side of the mask, said filter assembly providing a passage for air received from the environment and/or a discrete air supply system into the interior of the mask.

13. A mask as claimed in claim 12, in which the filter assembly comprises a filter housing in communication with the exterior of the mask for receiving air from the environment, and in communication with the interior of the mask, wherein the filter housing, in use, houses a filter which filters the air passing through it.

14. A mask as claimed in claim 12 or claim 13, wherein the filter is formed from a series of filter regions arranged so that different particulates and/or toxic gases are sequentially removed from the air passing through the filter.

15. A mask as claimed in any preceding claim, in which the mask is a full face mask having an integral nose and mouth cup.

16. A mask as claimed in any preceding claim, comprising at least one filter in communication with the environment for filtering air from the environment, and means sealed from the environment for supplying air from an air source to the interior of the mask, in which, in use, air is automatically drawn through the filter from the environment when the wearer's demand for air exceeds the amount supplied by the air source.

17. A mask as claimed in any preceding claim, comprising at least one filter in communication with the environment for filtering air from the environment, and means sealed from the environment for supplying air from an air source to the interior of the mask, in which the means for supplying air from the air source supplies air to the interior of the mask via the filter.