It is known to use face masks in order to provide protection from air pollution. Particular users include commuters walking, jogging or cycling to work. Known face masks suffer from a number of problems. For example, they cover the user's nose and can therefore be uncomfortable and make swallowing difficult. Although the area of the filter may be considerable, a large proportion of the filter is against the user's face to ensure a close fit for the mask and is therefore ineffective. Further, known face masks are often made of materials which do not allow the skin to breathe and therefore trap moisture. In hot weather and during exercise, the mask can quickly become saturated with moisture, thereby increasing its resistance to airflow and the load on the user's inspiratory muscles, as well as reducing its effectiveness as a filter. A major problem is that the filter is at the forward, exposed, side of the mask. In wet weather the filter can quickly become saturated and unusable. Moreover, exhaled air is generally not removed efficiently from the mask with the result that heat and moisture can build up within the mask, adding to the discomfort of the user, increasing the resistance to

airflow and reducing the efficiency of the filtration material.

It is therefore an object of the present invention to provide a respiratory protection device which overcomes or ameliorates at least some of the above-described disadvantages.

According to the present invention there is provided a respiratory protection device comprising: a housing defining a chamber within the housing; a mouthpiece communicating with the chamber; a filter for filtering air flowing into the chamber; and an outlet communicating with the chamber and provided with a non-return valve which is operable to allow air to flow out of the chamber.

Thus the device according to the invention allows a user to inhale, drawing air into the chamber through the filter and out of the chamber through the mouthpiece, and to exhale, urging air into the chamber through the mouthpiece and out of the chamber through the non-return valve of the outlet.

A small proportion of exhaled air may also pass out of the chamber through the filter, but the non-return valve presents no significant resistance to the passage of exhaled air.

The non-return valve may comprise a flap valve or umbrella valve. The non-return valve may be mounted in a recess within the surface of the housing.

The outlet may be substantially coaxial with the mouthpiece. The outlet may be elliptical in shape with the major axis adapted to extend laterally in use. The cross- sectional area of the outlet may correspond substantially to the cross-sectional area of the mouthpiece.

The mouthpiece may be provided with a radially outwardly flared portion adapted to be received in the mouth of the user, for example, behind the lips and in front of the teeth of the user. The mouthpiece may be elliptical in shape with the major axis adapted to extend laterally in use.

The chamber may extend laterally to one or both sides of the mouthpiece.

The housing may be provided with first and second opposing faces, the outlet being provided in the first face and the mouthpiece and the filter being provided in the second face. The remainder of the first face may be substantially continuous. In this way, the filter is positioned within "wings"extending on the same side of the housing as the mouthpiece and is therefore protected from rain ingress by the first (forward) face of the housing.

The housing and the filter may be curved so as in use to extend around the face of the user.

The filter may comprise a web of filter material mounted within a frame, the frame being mounted in a recess formed around the housing.

The filter may be mounted over a hollow member forming part of the housing. The hollow member may be of elliptical cross-section. The mouthpiece may be formed with a radially extending lip for retaining the filter in position on the hollow member.

For a better understanding of the present invention and to show more clearly how it may be carried into effect reference will now be made, by way of example, to the accompanying drawings in which:

Figure 1 is an exploded front perspective view of one embodiment of a respiratory protection device according to the present invention ; Figure 2 is an exploded plan view of the respiratory protection device shown in Figure 1 ; and Figure 3 is a rear perspective view of a housing of the respiratory protection device shown in Figure 1.

The respiratory protection device shown in the figures comprises a housing 1, a filter 3 and a mouthpiece 5.

The housing 1 includes a hollow member 7 of elliptical cross-section, the major axis of the ellipse being substantially horizontal. The hollow member 7 is provided with lateral openings 9 for the passage of air.

The housing 1 also includes a pair of wings 11 which extend laterally, one from each side of the hollow member 7. The wings 11 are of generally U-shaped cross-section and provide a substantially continuous (first) forward surface to resist the ingress of rain or the like into the device.

The wings 11 are curved so as to extend in use around the face of the user and the outer ends of the wings are closed at 13.

An upright supporting bar 15 extends along the minor axis of the hollow member 7 across the outlet 16 of the hollow member. An umbrella valve 17 is secured to the supporting bar by means of a mushroom shaped protrusion 18 extending from a rear face of the valve and passing through an aperture 20 provided substantially in the middle of the bar 15. The umbrella valve 17 is made of a resilient material, such as an elastomeric material, and the domed side of the protrusion 18 allows the protrusion to pass through the aperture 20, while the flat under surface retains the valve in position. The umbrella valve 17 is recessed into the outlet 16 of the hollow member, the recess being shown at 19. Recessing the valve in this way minimises the risk of the valve becoming caught, and potentially damaged, when it is stored, such as in a bag. Alternatively or additionally, a (removable) protective guard may be provided for the valve.

As an alternative to the protrusion 18, the umbrella valve could be secured to the supporting bar by other suitable means, such as an adhesive.

The rearward edge of the curved forward surface provides a second face opposing the first face and is recessed at 21 on each side of the hollow member 7 to receive the filter 3 as will be explained in more detail hereinafter. The

filter, in conjunction with the housing 1, forms a chamber 22 within the housing at each lateral side of the hollow member 7.

The filter 3 comprises a substantially elliptical central section 23 with two laterally extending frames 25. A web 27 of a suitable filter material of any well known form is secured within each generally rectangular area defined by the central section 23 and the frame 25. As an alternative to a conventional untreated filter material, the filter material may comprise one or more of: an electrostatic filter material, a filter material incorporating activated carbon, a filter material incorporating an open cell foam incorporating activated carbon, and a filter material incorporating an open cell foam coated with a hygroscopic substance. The web 27 may be secured to the frames 25 by laminating such that the web is on that side of the filter 3 within the housing 1. The frames 25 are curved so as to extend in use around the face of the user in the same manner as the wings 11 of the housing.

The central section 23 of the filter 3 is dimensioned so as to be a push fit over the hollow member 7, with the central section occupying the recesses 21 provided in the rearward edge of the curved forward surface. The frames 25 are a close fit within the area defined by the curved forward

surface such that the housing 1 and the frame 3 co-operate to form a chamber which extends the entire length of the device, that is over the length of both wings 11. Thus the chamber provides a substantially unobstructed passage for air which is drawn in through the filter by a user.

In use, a substantially air-tight seal is formed between the filter 3 and the housing 1.

The mouthpiece 5 is substantially elliptical in cross- section with the major axis of the ellipse being substantially horizontal. The mouthpiece 5 is formed with an axially extending flange 28 which is dimensioned to be a close fit within the hollow member 7. The mouthpiece is also formed with a radially outwardly extending lip 29 which may serve to retain the filter 3 in position on the hollow member 7. Alternatively or additionally, the frames 25 of the filter 3 may be held in place within the housing 1 by friction or the like.

As best shown in Figure 2, on that side of the mouthpiece remote from the flange 28, the outer surface of the mouthpiece is curved in the axial direction such that the cross-sectional area reduces and subsequently increases to form a flared region 31 which is adapted to be received in the mouth of the user between the lips and teeth of the

user. Thus, the mouthpiece offers protection similar to a gum shield.

The mouthpiece 5 and the outlet 16 of the hollow member are substantially coaxial so as to allow substantially unobstructed passage of air from the mouthpiece to the outlet when the user exhales.

As an alternative to laminating the web 27 to the frames 25, the web 27 may be separate and may be provided with means, such as lugs or the like, for engaging with the frames in order that the web may be removed and replaced as required by the user. In such a case, the frames 25 could be integral with the mouthpiece 5.

The components of the device may be made of any suitable material. For example, the components may be made of polyethylene which is an FDA compliant material and can readily be moulded in different hardnesses. The mouthpiece, at least, should be relatively flexible in order to be comfortable in use and not to present a hazard in the event of an accident. Polyethylene has several advantages. For example, it can be sterilised by immersion in boiling water and can be made from renewable resources and can readily be recycled or incinerated to recover energy.

If desired, the device may be provided with a cord which will in use extend loosely around the neck of the user in order that the user does not need to hold the device when it is not in use. In this way, the device can readily be taken out and replaced, for example when waiting at traffic lights.

In use of the respiratory protection device according to the present invention, the device is first assembled with the mouthpiece 5 securing the filter 3 in position relative to the housing 1. The cord is positioned around the user's neck and the device is ready to use.

The mouthpiece is inserted into the user's mouth between the lips and the teeth and in this position gives rise to relatively little saliva build-up, allows clenching of the teeth and does not inhibit swallowing as compared with a conventional mouthpiece which is positioned behind the teeth of the user. Further, the device according to the present invention does not cover the nose of the user because it has been found that above relatively low levels of exercise all inspiration takes place through the mouth.

During expiration the umbrella valve 17 flexes to allow exhaled air to pass through the outlet 16 with little or no resistance, while during inhalation the valve 17 is drawn

against the housing to seal therewith and air is therefore drawn into the chamber through the filter 3.

The filter material is initially a bright white colour but visibly changes from white to grey with use as particulates and other polluants are trapped in the filter. When the filter needs to be changed this can be readily accomplished simply by removing the mouthpiece from the hollow member 7, removing the filter 3 replacing the used filter with a new one, and replacing the mouthpiece.

The filter material is positioned on that side of the housing adjacent to the face of the user. That is, the filter is between the continuous face of the housing and the face of the user and is therefore protected from rain and spray.

The filter material is not obstructed in any way, for example due to contact with the face of the user, and the entire surface area of the filter material is therefore able to pass air into the chamber and to the mouthpiece with very little obstruction and therefore without applying any significant stress to the inspiratory muscles of the user thereby minimising the additional work of breathing.