GB2189152A - Emergency escape breathing apparatus - Google Patents

Abstract

In emergency escape breathing apparatus oxygen 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. Passage of both inhaled and exhaled gases between the interior of the half mask 5 and the interior of the hood 1 occurs through carbon dioxide absorbent material (8 or 11) located either in the walls of the half mask 5 (Figs. 1 and 2 not shown) or in a container (10) outside of the hood 1 near to the visor part of the hood 1 (Fig. 3 (not shown)). <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 positioned within the hood for engaging the face of the wearer of the hood around the nose and mouth, and porous means for retaining a material capable of absorbing carbon dioxide in a location so related to the half mask that the gases both inhaled and exhaled by the wearer pass through said carbon dioxide absorbent material.

The emergency escape breathing apparatus of the present invention thus erhploys pendulum breathing. The double passage of gas through the carbon dioxide absorbent material enables a good scrubbing of carbon dioxide from the breathable gas to be obtained with a relatively small quantity of carbon dioxide absorbent material.

The carbon dioxide absorbent material may be provided either within the hood or in a container attached to the outside of the hood.

When the carbon dioxide absorbent material is provided within the hood it is preferably retained between layers of porous material in a sandwich structure in the walls of the half mask. However, the carbon dioxide absorbent material may be provided in a container or canister in a gas passage which is outside the hood and which communicates both with a half mask of impermeable material and with the interior of the hood outside the half mask.

Preferably the container or canister is mounted to the outside of the hood.

In the alternative arrangement wherein the carbon dioxide absorbent material is in a container or canister mounted to the outside of the hood, the container or canister is advantageously mounted on the outside of a visor part of the hood so that the container may readily communicate with the interior of the hood both within the half mask and outside the half mask. The carbon dioxide absorbent material is retained within the container by porous means such as porous screens and the gas breathed by the wearer of the hood is exhaled through the carbon dioxide absorbent material into the interior of the hood outside the half mask.

The container may be entirely filled with carbon dioxide absorbent material or it may have a central empty chamber from which the gas passes through porous means such as screens into the carbon dioxide absorbent material.

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 preferred embodiments thereof which will be described,by way of example, with reference to the accompanying diagrammatic drawings in which: Figure 1 shows emergency escape breathing apparatus according to the invention with the hood in position over the head of a wearer, Figure 2 is an enlarged view of the part of the hood incorporating the half mask and showing the carbon dioxide absorbent material, and Figure 3 is a view similar to Figure 2 of another embodiment of the invention in which the carbon dioxide absorbent material is located outside the hood of the emergency escape breathing apparatus.

In the drawings the same or similar parts are designated by like reference numerals.

Referring to Figure 1 of the accompanying drawings, 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 oxygen through a flexiblepipe 2 from a source of oxygen under pressure such as the cylinder 3, the gas supply being initiated by turning a simple on/off valve 4. Alternatively to the on/off valve 4, 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 a 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 of the hood, 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 through which the wearer will see.

The half mask 5 may be of simple shape such as a tube or tunnel as illustrated in Figure 1 or it may be shaped in the more sophisticated manner conventionally provided as a half mask within a full face mask of known breathing apparatus. 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 retains the hood in a position enveloping the whole of the head of the wearer. The elastic neck band 7 also constitutes a seal adequate to prevent toxic gases entering the hood 1. Optionally a simple exhale valve (not shown) may be fitted to the hood to prevent undue build-up òf pressure in the hood.

In accordance with one embodiment of the present invention the half mask 5 is constructed to incorporate a material capable of absorbing carbon dioxide, for example particles of soda lime. This embodiment of the invention is illustrated in Figure 2 of the accompanying drawings where the walls of the half mask 5 are shown to be of a sandwich construction in which a carbon dioxide material 8 is retained between layers 9 of a porous material such as an open cell foamed plastics material, for example foamed polyvinyl chloride or foamed polyurethane.

In operation all gases breathed by the wearer of the hood 1 containing the half mask of Figure 2 in both inhalation and exhalation are caused to pass through the walls of the half mask 5 in a pendulum breathing operation. On each pass carbon dioxide present in the gases is absorbed by the soda lime or other carbon dioxide absorbent material 8. In this way the amount of carbon dioxide remaining within the hood is kept to a level at which no inconvenience is caused to the wearer of the hood even though he may be forced to make vigorous physical movements while wearing the hood 1.

The absorption of carbon dioxide by soda lime or other carbon dioxide absorbent material is an exothermic process. In consequence heat is generated in the walls of the half mask 5 in the embodiment of Figure 2.

Such generation of heat may cause discomfort to the wearer of the hood 1, and an alternative embodiment of the present invention which reduces this possibility is illustrated in Figure 3 of the accompanying drawings.

In the embodiment of Figure 3 there is shown the hood 1 and the half mask 5 which in this case is made of an impermeable material such as rubber. A container 10 is mounted to the outside of the hood 1 near to the visor part of the hood 1, the container 10 containing soda lime or other carbon dioxide absorbent material 11 retained by an arrangement of porous screens 12 so as to permit pendulum breathing via the half mask 5 through the container 10 into the interior of the hood 1 outside the half mask 5 and back from the interior of the hood 1 through the container 10 via the half mask 5 to the user.

The flow of gases in this pendulum breathing is illustrated by arrows 13 and 14.

The container 10 is preferably made of thinwalled metal, such as aluminium, so as to provide good heat transfer to the external atmosphere, thus aiding cooling of the exhaled gases. The container 10 may even incorporate simple cooling fins.

The container 10 may have any suitable shape, for example it may be cylindrical in shape in which case the container 10 illustrated in Figure 3 has two sections, an outer annulus containing the carbon dioxide absorbent material 11 and an.inner empty chamber.

Alternatively, the container 10 can be designed as a rectangular three chamber box in which case the carbon dioxide absorbent material 11 is contained in upper and lower chambers separated from the central empty chamber by porous screens 12.

As a further alternative the container 10 can be designed without any central empty chamber but with the porous screen 12 coincident with the portion of the hood 1 which is within the half mask 5, so that the half mask 5 communicates directly through the porous screen with the carbon dioxide absorbent material.

The amount of soda lime or other carbon dioxide absorbent material is calculated to cope with the maximum amount of carbon dioxide likely to be produced during an escape and is preferably adequate for about twice the expected time to escape, i.e. about ten minutes.

The embodiment of the invention illustrated in Figure 3 is easier to assemble than the embodiment of Figure 2 and is cooler in operation.

As an alternative to the open cell plastic foam, the layers 9 of porous material and the porous screens 12 may be fine metal gauze, mineral wool, glass fibre filter paper, or any other material which will both retain soda lime dust and offer low resistance to breathing gas flow.

Although the emergency escape breathing apparatus described herein utilises the oxygen cylinder as a source of breathing gas it will be understood that the apparatus may equally be used with a source of compressed air or oxygen-enriched air.

Claims (7)

1. Emergency escape breathing apparatus comprising a hood of transparent plastics material which includes a half mask positioned within the hood for engaging the face of the wearer of the hood around the nose and mouth, and porous means for retaining a material capable of absorbing carbon dioxide in a location so related to the half mask that the gases both inhaled and exhaled by the wearer pass through said carbon dioxide absorbent material.

2. Emergency escape breathing apparatus according to Claim 1, wherein the porous means is provided by layers of porous material retaining the said carbon dioxide absorbent material in the walls of the half mask.

3. Emergency escape breathing apparatus according to Claim 1, wherein a container for the said carbon dioxide absorbent material is mounted on the outside of the hood, the said container permitting gas flow from the half mask to the interior of the hood outside the half mask through porous means retaining the said carbon dioxide absorbent material within the container.

4. Emergency escape breathing apparatus according to Claim 3, wherein the exhaled gases pass through the half mask into a central space within the container before passing through porous screens into the carbon dioxide absorbent material.

5. Emergency escape breathing apparatus comprising a hood of a heat resistant transparent plastics material for enveloping the head of a wearer, a source of oxygen under pressure, and means for passing oxygen from the said source to the interior of the hood, the hood including a visor part near which a half mask is mounted within the hood, 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, and the walls of the half mask including layers of porous material retaining therebetween a material capable of absorbing carbon dioxide, the walls of the half mask including the said layers and the carbon dioxide absorbent material constituting the sole means by which gas may pass from the interior of the half mask to the other space within the hood.

6. Emergency escape breathing apparatus comprising a hood of a heat resistant transparent plastics material for enveloping thehead of a wearer, a source of oxygen under pressure, and means for passing oxygen from the said source to the interior of the hood, the hood including a visor part, a half mask mounted to the inside of the hood near the visor part, and a container having carbon dioxide absorbent material therein mounted to the outside of the hood near the visor part, 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 container permitting gas flow to the interior of the half mask and the interior of the hood outside the half mask through porous means retaining the said carbon dioxide absorbent material within the container, and all gas flow between the interior of the half mask and the interior of the hood outside the half mask being through the said container.

7. Emergency escape breathing apparatus substantially as hereinbefore described with reference to the accompanying drawings.