GB2189153A - Emergency escape breathing apparatus - Google Patents

Abstract

In emergency escape breathing apparatus air or other breathable gas is supplied to the interior of a hood 1 which envelopes the head of a wearer. A half mask 5 mounted near a visor part of the hood 1 engages the nose and mouth of the wearer so that the gases breathed by the wearer are inhaled from and exhaled to the interior of the half mask 5. Gases pass between the interior of the half mask 5 and the interior of the hood 1 during both inhalation and exhalation, but, when the pressure within the half mask rises during the latter part of the exhalation, an exhale valve 8 mounted within the half mask opens and allows the exhaled gases containing the major part of the carbon dioxide to be expelled into the surrounding atmosphere. Preferably the walls of the half mask 5 are formed of a porous material such as open cell foamed plastics material. <IMAGE>

Description

SPECIFICATION Emergency escape breathing apparatus This invention relates to emergency escape breathing apparatus.

It is known to provide, emergency escape breathing apparatus which comprises a hood of transparent plastics material affording all round vision to the wearer, and a compressed air, or oxygen, breathing set supplying breathable gas to the interior of the hood at a predetermined constant rate of flow for a minimum predetermined duration dependent on the size of the gas cylinder. The hood is of a size which can be worn over the head of a wearer of any age or hair-style, without any adjustment and irrespective of whether the wearer is bearded or wears spectacles. The hood has an elastic neck band past which exhaled gas leaves the hood at a rate determined by the gas flow to the hood.

This known emergency escape breathing apparatus is designed for use in escaping from a location where there may be a toxic or otherwise irrespirable atmosphere, for example a room or corridor which is filled with smoke as a result of a fire. The user simply starts the flow of breathable gas to the hood, pulls the hood over his head, and proceeds through the irrespirable atmosphere to a place of safety.

While this equipment provides adequately for the escape of personnel in most circumstances, a difficulty can arise when panic occurs or undue exertion is necessary in order to escape, such as from the cabin of a civil aircraft containing many passengers some of whom may be overcome by fumes before they have time to don their emergency escape breathing apparatus. In such cases the panic or physical exertion necessary to climb over seats or over or past other obstacles can result in an unacceptable level of carbon dioxide building up within the hood with consequent risk to the wearer of the emergency escape breathing apparatus.

This difficulty can be overcome by increasing the preset rate of flow of breathable gas to the hood. However this action results in an undesirable reduction in the time for which breathable gas is supplied to the hood unless the gas supply is increased by providing a larger gas cylinder. A larger gas cylinder is heavier and adds to the weight carried by the user and to the exertion necessary to escape from the hazard area, so this is not a satisfactory solution to the problem.

According to the present invention there is provided emergency escape breathing apparatus comprising a hood of transparent plastics material which includes a half mask mounted to the inner surface of the hood near a visor part of the hood for engaging the face of the wearer of the hood around the nose and mouth, the half mask including means permitting exhaled gas to pass from the interior of the half mask to the interior of the hood outside the half mask at all stages of exhalation, and an exhale valve mounted in the hood, within the half mask,for allowing exhaled gas to escape from within the half mask to the surrounding atmosphere when the pressure of exhaled gas within the half mask reaches a predetermined level.

The expression "half mask" is not to be interpreted as restricted to the sophisticated shape of half mask conventionally used inside a full face mask but may also include an essentially simple ring of porous material mounted to or near the visor part of the hood, for example by adhesive, the ring extending to a position at which it may engage the face of the wearer of the hood around the nose and mouth in a manner to ensure that all gases breathed by the wearer come from within the ring of porous material. Preferably the half mask is constructed of an open cell foamed plastics material such as polyvinyl chloride or a polyurethane. However the porous material constituting the wall of the half mask may form part only of the half mask, the remainder of the wall of the half mask being impermeable.

As a further alternative, the half mask may be constructed entirely of impermeable material, and the means permitting exhaled gas to pass from the interior of the half mask to the interior of the hood outside the half mask is an aperture through an impermeable wall of the half mask. The aperture is a small hole of a size to permit gas to flow freely through it only at low pressures, i.e. pressures less than half an inch water gauge.

Advantageously the exhale valve is set so that it opens when the pressure in the face mask reaches the higher pressure present in the second part of an exhaled breath. It is the second part of an exhaled breath which contains the major part of the carbon dioxide.

Accordingly, the major part of the carbon dioxide in the exhaled breath is ejected from the hood through the exhale valve whereas the oxygen present in the first part of the exhaled breath passes from the half mask into the remainder of the interior of the hood.

The pressure reached during the exhalation is from one to two inches water gauge and the exhale valve is conveniently set to open at a pressure of approximately half an inch water gauge.

When the emergency escape breathing apparatus of the present invention is designed for emergency escape from the cabin of a civil aircraft which is subject to fire, there is a risk of hot materials falling upon the wearer of the breathing apparatus and, in order that the breathing apparatus may withstand such application of hot materials, the hood is advantageously made from a clear plastics material which is capable of withstanding temperatures of the order of 200"C. The plastics material sold under the trade name Kapton is one example of a suitable material. In this specification the term "heat resistant transparent plastics material" is used to denote clear nondermatitic plastics materials which are capable of withstanding temperatures of the order of 200"C.

Conveniently the emergency escape breathing apparatus of the present invention includes elastic means extending round the back of the wearer's head for retaining the half mask in engagement with the face of the wearer of the hood.

The present invention will be further understood from the following detailed description of a preferred embodiment which is made by way of example with reference to the accompanying single figure of diagrammatic drawing.

Referring to the accompanying drawing, there is shown emergency escape breathing apparatus according to the present invention which includes a hood 1 of the heat resistant transparent plastics material obtainable under the name Kapton in position on the head of a wearer. The interior of the hood 1 is fed with air through a flexible pipe 2 from a source of compressed air such as the cylinder 3, the air supply being initiated by turning a simple on/off valve 4. Alternatively to the on/off valve, the apparatus may be fitted with a valve which turns on the gas supply automatically, either when the apparatus is taken from its packaging or when the hood is donned by the wearer.

The hood 1 of the present invention includes a simple half mask 5 secured to the inside of the hood 1 near that part of the hood 1 through which the wearer will look when the hood 1 is being worn. This part of the hood 1 is denoted herein as a visor part but the visor part may be an area of the hood 1 which differs from other parts of the hood 1 only in that, when the half mask is engaging the face of the wearer, as shown in Figure 1, it is the part of the hood 1 in front of the wearer's face.

The half mask 5 may be of simple ring shape forming a tube or tunnel as illustrated in Figure 1 or it may be shaped in the more sophisticated manner provided as a half mask within a conventional full face mask. The half mask 5 is formed of a porous material, such as open cell foamed polyvinyl chloride, which permits passage of gases. The half mask is conveniently retained in position against the face of the wearer by elastic 6 incorporated in the hood 1 and engaging the back of the wearer's head.

An elastic neck band 7 conveniently retains the hood 1 in a position enveloping the whole of the head of the wearer.

A low resistance exhale valve 8, e.g. a stepped rubber mushroom valve, is installed in the hood at the centre of the ring defining the half mask 5 to allow exhaled gases to escape from within the half mask 5.

Inhale gas enters the half mask 5 through the porous material constituting the walls of the half mask 5 from the main interior of the hood 1 to which air is fed from the cylinder 3.

When the wearer exhales, the first part of the exhaled breath passes through porous material constituting the half mask 5, but, as the pressure of the exhaled breath increases, for example to half an inch water gauge, the exhale valve 8 opens at the higher pressure resulting from the higher flow in the second half of the exhaled breath. The pressure drop through the porous material slightly exceeds the pressure drop through the exhale valve so that the exhale flow of the second part of the exhaled breath containing the major part of the carbon dioxide is preferentially through the exhale valve 8 to the surrounding atmosphere.

The construction of the emergency escape breathing apparatus incorporating an exhale valve within a half mask ensures that there is no undesirable build-up of carbon dioxide to inconvenience the wearer when escaping from an area such as the cabin of a civil aircraft where exertion on the part of the wearer may be necessary.

Although the emergency escape breathing apparatus described herein utilises an air cylinder as the source of breathing gas, the apparatus may equally be used with a source of oxygen-enriched air or a source of oxygen gas.

Claims (9)

1. Emergency escape breathing apparatus comprising a hood of transparent plastics material which includes a half mask mounted to the inner surface of the hood near a visor part of the hood for engaging the face of the wearer of the hood around the nose and mouth, the half mask including means permitting exhaled gas to pass from the interior of the half mask to the interior of the hood outside the half mask at all stages of exhalation, and an exhale valve mounted in the hood, within the half mask, for allowing exhaled gas to escape from within the half mask to the surrounding atmosphere when the pressure of exhaled gas within the half mask reaches a predetermined level.

2. Emergency escape breathing apparatus according to Claim 1, wherein the said means comprises porous material constituting the wall of at least part of the half mask.

3. Emergency escape breathing apparatus according to Claim 1 or Claim 2, wherein the half mask is constructed of porous material.

4. Emergency escape breathing apparatus according to Claim 2 or Claim 3, wherein the porous material is an open cell foamed plastics material.

5. Emergency escape breathing apparatus according to Claim 1, wherein the said means comprises an aperture through a wall of a half mask constructed of impermeable material.

6. Emergency escape breathing apparatus according to any one of the preceding claims, wherein the predetermined level at which the exhale valve is set to open is the higher pressure present in the second part of an exhaled breath.

7. Emergency escape breathing apparatus according to any one of the preceding claims, wherein the transparent plastics material of the hood is capable of withstanding temperatures of the order of 200"C.

8. Emergency escape breathing apparatus comprising a hood of a heat resistant transparent plastics material for enveloping the head of a wearer, a source of compressed air and means for passing air from said source to the interior of the hood, the hood including a visor part near which a half mask is mounted, the half mask being engageable with the wearer's face to cause all gas breathed by the wearer to be inhaled from or exhaled to the space within the half mask, the walls of the half mask being formed of an open cell foamed plastics material permitting passage of gases between the interior of the half mask and the remainder of the interior of the hood to which air is supplied, and an exhale valve being mounted in the part of the hood within the half mask, the exhale valve being set to open when the pressure within the half mask reaches the higher pressure present in the second part of an exhaled breath.

9. Emergency escape breathing apparatus substantially as hereinbefore described with reference to the accompanying drawing.