GB2234440A

GB2234440A - Respiratory protective apparatus

Info

Publication number: GB2234440A
Application number: GB8916448A
Authority: GB
Inventors: Michael Harvey Glynn; Simon Kugler
Original assignee: Sabre Safety Ltd
Current assignee: Sabre Safety Ltd
Priority date: 1989-07-19
Filing date: 1989-07-19
Publication date: 1991-02-06
Anticipated expiration: 2009-07-19
Also published as: GB8916448D0; DE4023013A1; GB2234440B; FR2649897A1

Abstract

Respiratory protective apparatus incorporates a flexible hood 1 which encloses the head of a wearer and which has a neck seal 2 engaging the neck of the wearer and excluding noxious atmospheric gases from the space within the hood 1 and the neck seal 2. A breathing bag 3 is connected to the hood by first and second channels 5, 7 and a canister 8 of potassium superoxide is included in one of the two channels for absorbing carbon dioxide from exhaled gas and producing an equivalent quantity of oxygen. An accumulation of carbon dioxide in the gas inhaled by the wearer of the hood 1 is avoided, without the need for providing an inner half mask or a noseclip and mouthpiece, by providing a fan 14 or other air mover which withdraws gases from the hood 1 to the breathing bag 3 through one of the channels 5 and ensures that the gases pass through the canister 8 of potassium superoxide before being re-presented to the hood 1 through the other channel 7 for inhalation by the wearer of the hood 1. <IMAGE>

Description

-I- RESPIRATORY PROTECTIVE APPARATUS This invention relates to respiratory

protective apparatus.

An essential integer of respiratory protective apparatus is a protective means for surrounding the respiratory passages of a wearer of the protective apparatus. The protective means may be a full face mask or a half mask which engages the face to enclose the nose and mouth only of the wearer or it may be a hood which envelopes the whole head of the wearer.

Respiratory protective apparatus incorporating a hood and a cylinder of breathable gas such as air or oxygen is already known for use in escape equipment such as for escape from a fire on board a ship or in aircraft. A hood may also be used with compressed air-line equipment, for example, in nuclear power stations or when servicing chlorine installations in swimming pools. Furthermore, hoods may be used with fresh air equipment, i.e. connected via an airline to a source of fresh air some distance from the wearer.

When a hood is used it will be fitted with a neck seal to limit the ingress of toxic gases from the surroundings and preferably the neck seal may be a diaphragm of highly elastic polymer such as 1 -2silicone or polyurethane with a small central hole. The elasticity of the material allows this hole to be expanded sufficiently to pass over the head of the wearer when donning the hood and the hole then rapidly shrinks to fit around the neck and provide an excellent seal.

It is also known to provide a hood or a full face mask with a canister containing a chemical material which will absorb or "scrub" the carbon dioxide from the exhale gas and simultaneously generate oxygen to maintain a satisfactory level of oxygen in the gas which is then returned to the wearer for rebreathing. In such a system, it is important to minimise the volume of gas adjacent to the mouth and nose, otherwise the carbon dioxide level in the inhale gas will rise due to rebreathing of exhale gas which has not been scrubbed. This can be done by providing an inner orinasal or half mask with an inhale valve and an exhale valve.

It is an object of the present invention to provide respiratory protective apparatus in whi-ch an adequate supply of inhale gas with a low carbon dioxide concentration is made available for the wearer in a simple manner.

According to the present invention, there is provided respiratory protective apparatus comprising protective means for surrounding the respiratory passages of a wearer thereof to exclude noxious atmospheric gases from the space within the protective means and adjacent to the said respiratory passages. porous means retaining a chemical material which is capable of both absorbing carbon dioxide ad generating oxygen, and air moving means for causing gases exhaled by the wearer to pass through the chemical material in the porous means and be re-presented for inhalation by the wearer.

The protective means may be a full face mask enclosing the whole of the wearer's face, including the eyes, and having first and second channe ls providing connections from the full face mask to a reservoir of breathable gas such as a breathing bag.

Alternatively the protective means may be a flexible hood enclosing the head of the wearer and carrying a neck seal for engaging the neck of the wearer. When a flexible hood is used, the hood itself may constitute a reservoir of breathable gas, and both the air moving means and the porous means retaining the chemical material may be located within the hood, the air moving means being so positioned in relation to the chemical material that gas is either driven or sucked through the chemical material to maintain a low level of carbon dioxide and a sufficient level of oxygen in the breathable gas.

In a preferred embodiment of the present invention which will be described, the protective means is a flexible hood connected by first and second channels to a separate reservoir of breathable gas in a breathing bag. The air moving means, which is preferably a fan, may conveniently be located within the breathing bag.

In all embodiments of the present invention, the use of the fan or other air moving means has the effect of maintaining a good circulation of breathing gas through the chemical material so that there is always an adequate supply of inhale gas with low carbon dioxide concentration and adequate oxygen concentration available without the necessity of providing an inner orinasal or half mask within the protective means, whether this is a hood or a full face mask.

Advantageously, the fan circulates gases through the chemical material at a rate faster than the rate at which the wearer of the protective means is breathing.

In accordance with a preferred embodiment of the present invention there is provided respiratory protective apparatus comprising a flexible hood for enclosing the head of a wearer, a neck seal carried by the hood for engaging the neck of the wearer to exclude noxious atmospheric gases from the space within the hood and the neck seal, a breathing bag, first i and second channels connecting the space within the hood and the neck seal to the breathing bag, one of the first and second channels including porous means retaining a chemical material which is capable of both absorbing carbon dioxide and generating oxygen, and a fan located in the breathing bag and operative to move gases through the chemical material in the said porous means.

The porous means retaining the chemical material may be located in either of the first and second channels which respectively pass gases from the hood to the breathing bag and pass gases back to the hood for inhalation. When the porous means is in the f irst channel, the fan is arranged to suck exhaled gases through the chemical material in the porous means and, when the porous means is in the second channel, the fan is conveniently arranged to drive gases from the breathing bag through the chemical material in the porous means.

The second channel may include a further breathing bag, in which case the porous means may be located between the breathing bag and the further breathing bag. In such an arrangement the fan may be located in the second breathing bag and suck gases through the porous means.

Conveniently, a cooler is located on the i - 6downstream side of the porous means, either adjacent to the porous means or spaced from it. In the latter case, for example, the porous means could be located in the first channel and the cooler be located in the second channel.

Also in one embodiment of the invention which will be described the first channel includes an exhale valve, conveniently at the junction between the first channel and the interior of the hood. The second channel may include an inhale valve located between the further breathing bag and the space within the hood and the neck seal. Preferably, the further breathing bag is connected to the first channel through a pressure relief valve.

1 The fan may be driven by a battery-operated electric motor located within the breathing bag or by an electric or other motor mounted outside the breathing bag.

Although, in the preceding description, one embodiment of the present invention has been described above as having two breathing bags, these may be regarded as two parts of a single breathing bag, the parts being separated from one another by the porous means and, optionally, a cooler. Advantageously, the two parts of the breathing bag, or the two breathing bags, however they may be regarded, are stowed inside a lower part of the hood so that they are afforded

1 1 1 a degree of protection from hot particles in the atmosphere.

In another embodiment of the present invention which will be described, however, only one breathing bag is used.

The present invention will be further understood from the following description of preferred embodiments thereof which is made, by way of example, with reference to the accompanying diagrammatic drawings in which:

Figure 1 is a side view in part cross-section of one embodiment of respiratory protective apparatus according to the present invention including a hood, Figure 2 is a side view in part cross-section of an alternative arrangement of breathing bag for the apparatus of Figure 1 in which the oxygen cylinder is positioned outside the breathing bag, Figure 3 is a side view in part cross-section of another embodiment of respiratory protective apparatus including a hood, and Figure 4 is a side view in part cross-section of a further embodiment of respiratory protective apparatus according to the invention.

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 a flexible hood 1 made of a transparent 1 -8flame resistant material such as that obtainable under the Registered Trade Mark "KAPTON" or of a commercially available flame resistant composite formed of a suitable plastics material laminated to a woven base, the composite including avisor (not shown) of a rigid transparent plastics material, for example "Perspex" (Registered Trade Mark) or polycarbonate.

A neck seal 2 consisting of a septum of highly elastic polymer such as silicone or polyurethane is secured to a suitable part of the interior of the hood 1, for example by welding or adhesive, for engaging the neck of the wearer to provide a good seal.

Stowed inside a lower part of the hood 1 are breathing bags 3 and 4, a f irst breathing bag 3 being connected to the space within the hood 1 and the neck seal 2 by a first channel 5. A non-return exhale valve 6 is provided at the junction of the first channel 5 with the neck seal 2.

The first breathing bag 3 is also connected to the space within the hood 1 and the neck seal 2 via a second channel 7 which includes the second breathing bag 4, a canister 8 containing a chemical material such as potassium superoxide which, in the presence of moisture, will react with the carbon dioxide in the exhale gas to give off oxygen, and a cooler 9. The cooler 9 is provided because the chemical reaction -9of absorbing carbon dioxide and generating oxygen in the canister 8 is exothermic so that the gas becomes heated. The cooler 9 may be in the form of a dispersed mass of metal such as a sintered metal block or a pad of wire wool or it may be in the form of a chemical cooler utilising the latent beat of a suitable chemical to provide cooling or of an extended passage enabling beat loss to the ambient atmosphere.

The channel 7 additionally includes an inhale valve 10 situated between the upper or second breathing bag 4 and the space within the hood 1 and neck seal 2.

The gas circuit is completed by providing a bypass 11 from the upper or second breathing bag 4 into the first channel 5 via a relief valve 12.

Mounted within the first breathing bag 3 is a small fan 14 which is fitted in such a position as to propel gas from the first breathing bag 3 through the canister 8 and the cooler 9 to the interior of the second breathing bag 4. In the embodiment illustrated diagrammatically in Figure 1, the fan 14 is driven by a small intrinsically safe electric motor 13 powered by a battery 15 and also located within the first breathing bag 3.

In operation, the electric motor 13 is switched on when the hood 1 is removed from its stowage or when it is donned, and the fan 14 immediately starts operating to drive gases from the first breathing -10bag 3 through the canister 8 and cooler 9 into the second breathing bag 4. When the wearer of the hood 1 inhales, inhale valve 10 opens and breathable gas is drawn into the interior of the hood 1 and the neck seal 2 for inhalation.

When the wearer of the hood 1 exhales, the inhale valve 10 closes and the exhale valve 6 opens permitting exhaled gases to pass into the first channel 5. The action of the fan 14 draws the exhaled gases through the channel 5 into the first breathing bag 3. The fan 14 is set such that it is moving gas from the first breathing bag 3 into the second breathing bag 4 through the canister 8 and the cooler 9 at a faster rate than the wearer of the hood 1 is breathing so that exhaled gases are removed from the interior of the hood 1 and the neck seal 2 before the wearer of the hood 1 commences to inhale. Thus, when the wearer commences to inhale and inhale valve 10 opens, the wearer benefits directly from the gases which have been scrubbed of carbon dioxide and replenished with oxygen by passage through the canister 8. These gases enter the interior of the hood 1 and the neck seal 2 via the inhale valve 10 and the upper part of channel 7.

Since the fan 14 is operating to direct gas through the canister 8 and cooler 9 into the second breathing bag 4, the pressure in the second breathing bag 4 may increase to an undesirable level. This is prevented by the pressure release valve 12 and A k bypass 11 which permit excess gas to be returned from the second breathing bag 4 to the first breathing bag 3 via the lower section of channel 5.

The system is preferably designed for an average breathing flow of 40 litres per minute with the two breathing bags 3 and 4 providing a buffer volume to cope with the variation of flow during the inhale and exhale phases of the breathing cycle.

Figure 2 shows an alternative arrangement in which the motor 13 is positioned within the first breathing bag 3 but is driven by a battery 15 positioned outside the first breathing bag 3.

In other alternatives which. are not illustrated there could be a remote drive from an electric or hydraulic motor or turbine outside the breathing bag 3 to the fan 14.

In the embodiment of the present invention illustrated in Figure 3 the inhale and exhale valves are omitted together with bypass 11 and pressure relief valve 12, but the apparatus is otherwise similar to the apparatus of Figure 1. The fan 14 creates a continuous circulation of gas from the first breathing bag 3 through the canister 8, cooler 9, the second breathing bag 4, the interior of the hood 1 and the first channel 5 back to the first breathing bag 3. This circulation of gas is at a rate faster than the rate of breathing of the wearer of the hood 1 with i 1.

-12the result that carbon dioxide scrubbed and oxygenenriched gas is available for every breath taken by the wearer of the hood 1.

Figure 4 of the accompanying drawings shows a modified version of the embodiment of the invention illustrated in Figure 3 in which the second breathing bag 4 is omitted and the second channel 7 comprises essentially the canister 8, which is located outside, rather than inside, the breathing bag 3, and the cooler 9.

Respiratory protective apparatus in accordance with the present invention is demand sensitive. The carbon dioxide produced by a person depends on his or her weight and work rate. At a low work rate, the quantity of carbon dioxide is correspondingly low, and at a high work rate it is high. However, the oxygen produced by the potassium superoxide or similar chemical material is directly proportional to the carbon dioxide absorbed. Thus, when the work rate is low, so is the oxygen produced, but a change to a high work rate results in an almost immediate response in oxygen production. Thus oxygen and carbon dioxide absorption capacity are both saved during periods of low work rate. This contrasts with a conventional system using a carbon dioxide absorbent filter and a source of oxygen such as an oxygen cylinder or a cblorate candle, in which, unless a demand valve 1 i 4 1 -13is fitted, oxygen is supplied at a pre-determined rate, regardless of work rate.

In an emergency, it may be necessary to provide a quick initial burst of oxygen to fill the bood before sufficient carbon dioxide and moisture has been generated by the wearer to procure a full chemical reaction in the potassium superoxide in canister 8. The canister 8 of potassium superoxide is therefore fitted with a small starter which is well known in the art, such as a small cblorate candle with a cartridge which is arranged to be fired when the bood 1 is taken from its package. Alternatively, a plunger is arranged to pierce a small volume of acid which, flowing into the potassium superoxide in canister 8, starts the reaction. Other well-known starting methods may be used as convenient so that the potassium superoxide becomes operative as the hood 1 is unpacked and donned.

The preferred embodiments of the present invention which have been described provide respiratory protective apparatus incorporating a bood which encloses the bead of the wearer and in which an adequate supply of breathable gas with low carbon dioxide concentration is always available for inhalation without the necessity of providing an inner half or orinasal mask within the bood. This result is achieved by maintaining a good circulation of the breathing gas through the 1 I canister 8 of superoxide or similar chemical material, capable of absorbing carbon dioxide and generating oxygen, the rate of flow of the gas through the canister 8 being f aster than the rate of use of the breathing gas by the wearer of the bood.

0 4

Claims

CLAIMS:

1. Respiratory protective apparatus comprising protective means for surrounding the respiratory passages of a wearer thereof to exclude noxious atmospheric gases from the space within the protective means and adjacent to the said respiratory passages, porous means retaining a chemical material which is capable of both absorbing carbon dioxide and generating oxygen, and air moving means for causing gases exhaled by the wearer to pass through the chemical material in the porous means and to be re-presented for inhalation by the wearer.

2. Respiratory protective apparatus according to Claim 1 wherein the protective means is a flexible hood enclosing the head of the wearer and the hood carries a neck seal for engaging the neck of the wearer.

c

3. Respiratory protective apparatus according to laim 1 wherein the protective means is a full face mask.

4. Respiratory protective apparatus according to any one of the preceding Claims wherein the air moving means circulates gases through the said chemical material at a rate faster than the rate at which the wearer of the protective means is breathing.

1

5. Respiratory protective apparatus comprising a flexible hood for enclosing the head of a wearer, a neck seal carried by the hood for engaging the neck of the wearer to exclude noxious atmospheric gases from the space within the hood and the neck seal, a breathing bag, first and second channels connecting the space within the hood and the neck seal to the breathing bag, one of the first and second channels including porous means retaining a chemical material which is capable of both absorbing carbon dioxide and generating oxygen, and a fan located in the breathing bag and operative to move gases through the chemical material in the said porous means.

6. Respiratory protective apparatus according to Claim 5 wherein the second channel includes a further breathing bag, and the porous means retaining the chemical material is located between the breathing bag and the further breathing bag.

7. Respiratory protective apparatus according to Claim 6, wherein the second channel further includes a cooler located between the porous means and the further breathing bag.

8. Respiratory protective apparatus according to A:

Claim 6 or Claim 7 wherein the second channel includes an inhale valve located between the further breathing bag and the space within the hood and the neck seal.

9. Respiratory protective apparatus according to any one of Claims 6 to 8 wherein the further breathing bag is conected to the first channel through a pressure relief valve.

10. Respiratory protective apparatus according to any one of Claims 6 to 9, wheren the first channel includes an exhale valve.

11. Respiratory protective apparatus according to Claim 5, which further includes a cooler located in the second channel between the porous means retaining the chemical material and the space within the hood and the neck seal.

12. Respiratory protective apparatus according to any one of the preceding Claims wherein the chemical material is potassium superoxide.

_13. Respiratory protective apparatus constructed and arranged to operate substantially as hereinbefore described with reference to the accompanying drawings.

Published 1991 atThe Patent Office, State House. 66/71 High Holborn. IondonIkICIR47P. Further copies may be obtained from Sales Branch. Unit 6, Nine Mile Point. Cwmielinfach. Cross Keys. Newport, NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent,