BREATHING APPARATUS

Abstract: Breathing apparatus for aircraft passengers and others comprising: a) means (1) for supplying respiratory gases to a user, said supply means being detachably connectable to a first respiratory gas source (3), and thereby constituting a first oxygen supply system, said supply means including valve means (2), which valve means, when said supply means (1) is detached from the first respiratory gas source (3), automatically closes and prevents admission of noxious or hot gases into said supply means (1); b) means for supplying (5) or enabling supply (50) of a second respiratory gas source to said supply means (1), and constituting a second oxygen supply system, in which an absorption means (4) for absorbing carbon dioxide is included; and either c) means (6A) for automatically switching from said first oxygen supply system to said second oxygen supply system when said supply means (1) is detached from said first respiratory gas source (3); or c') means (6) for manually or automatically causing said second oxygen supply system to become operative to supplement or replace said first oxygen supply system, said second oxygen supply system continuing to be operable when said supply means (1) is detached from said first respiratory gas source (3).

Description: BREATHING APPARATUS This invention relates to breathing apparatus, particularly for aircraft passengers. In some aircraft accidents lives are lost due to the consequences of fire and in particular to the inhalation of smoke and fumes or hot gases. In some accidents passengers are overcome while still seated but do not show evidence of severe external burns. Some of these passengers could perhaps have been saved if a portable respirator, so called gas mask, had been available for each. Such devices can remove smoke and noxious gases by filtration and absorption. However, inhalation of very hot air, in the absence of noxious gases, can still cause death from thermal damage to the internal lining of the lungs. The use of a conventional gas mask would afford little or no protection against such very hot air. Furthermore in an aircraft fire noxious fumes from fuel and other sources may be present in such large amounts that normal filtration or absorption facilities can become blocked or exhausted. Additionally the fierce combustion of aircraft fuel can substantially reduce the oxygen content of the Cabin atmosphere. In patho-physiological terms alveolar burns,pulmonary oedema and shock may contribute to acute anoxia which may be of anoxic , anaemic, stagnant or histotoxic type or to a combination of some or all of these. Lives might also have been saved if each passenger had a portable respirator with self contained compressed air cylinder, as used by firemen and subaqua divers, but such apparatus is not practicable because of cost, weight and a high degree of skϋl and training required to use it. There are three main types of self contained breathing apparatus for aircraft passengers: firstly those which have filters to remove smoke and noxious gases, but these do not protect against hot gases; secondly those which provide a continuous supply of air or oxygen from a pressurised cylinder, but large volumes of gas are required and cylinders are heavy; and thirdly those which use pure oxygen in a rebreathing system with carbon dioxide absorber, but measures must be taken to maintain the absorbent material in good condition until it is needed and to remove nitrogen from the system. The efficiency of the absorbent material is dependent upon many chemical, physical and other factors. Importantly, the material deteriorates and becomes exhausted if it is exposed to air but frequent replacement is very expensive in maintenance costs. The activity is preserved for many months if the absorbent is sealed to prevent contact with air, which contains carbon dioxide and water vapour, but this is not easy to do. There is asubstantial amount of space between absorbent granules and this space is filled with air. If both ends of the container are sealed, the pressure within varies as the aircraft ascends and descends. This fluctuation may rupture the seal, even when there is a minimal volume of retained air. It is dangerous to rebreath air in the presence of an absorber, for acute anoxia may occur without warning, but pure oxygen is safe. Nitrogen should therefore be reduced but this should be achieved without waste of oxygen. The apparatus will be used by passengers without training or experience and with very little instruction. Thus the system should be simple to use and where possible automatic. It may also..have the oxygen source fixed to the conveyance means and may deliver oxygen to the reservoir. To reduce the risk of pure oxygen exacerbating a fire, an oxygen-rich atmosphere may be used rather than a pure oxygen atmosphere. If nitrogen wash out is not complete, the system is safe to use when the oxygen inflow is equal to or in excess of oxygen usage. If oxygen usage is in excess, then time is limited by the amount of oxygen remaining. A harness with adjustable straps may be used to retain a face mask in position and obtain a good fit to prevent gas leaks. Provision must also be made for children and for infants. It is an object of the present invention to at least minimize all the problems, including those which are peculiar in nature and intensity to aircraft fires, by the use of a simple, relatively inexpensive, portable breathing equipment. There are three main situations which can exist in an aircraft and which require safety means to operate. These are:- 1) Decompression 2) An in-flight fire 3) Escape of passengers from the aircraft on landing. Face masks connected to an oxygen supply are already provided in aircraft in case of sudden decompression at altitude. The user is supplied with a source of pure oxygen until the decompression problem has been solved. In the case of situations 2) and/or 3) an additional respiratory gas source is required which is independent of the oxygen supply already provided in aircraft. This additional respiratory gas source can be used to supplement the existing oxygen source in aircraft during an in-flight fire and/or the additional gas source can be utilised independently when escape from the aircraft on landing is necessary. Thus, the breatήing apparatus' of the present invention can be utilised for situations ' !) and/or 2) and/or 3) referred to above. Accordingly, in one aspect of the present invention, the breathing apparatus can be ' utilised to automatically switch from a first oxygen supply system to a second oxygen supply system, when supply of oxygen from said first supply system is terminated. In a further aspect of the present invention, said second oxygen supply system can be brought in to supplement the first oxygen supply system and thereafter the second system can itself continue to operate as a second system when supply of oxygen from the first system is terminated. According to the present invention there is provided breathing apparatus for aircraft passengers and others comprising: a) means for supplying respiratory gases to a user, said supply means being detachably connectable to a first respiratory gas source, and thereby constituting a first oxygen supply system, said supply means including valve means, which valve means, when said supply means is detached from the first respiratory gas source, automatically closes and prevents admission of noxious or hot gases into said supply means, b) means for supplying or enabling supply of a second respiratory gas source to said supply means, and constituting a second oxygen supply system, in which an absorption means for absorbing carbon dioxide is included; and either c) means for automatically switching from said first oxygen supply system to said second oxygen supply system when said supply means is detached from said first respiratory gas source; or c 1 ) means for manually or automatically causing said second oxygen supply system to become operative to supplement or replace said first oxygen supply system, said second oxygen supply system continuing to be operable-when said supply means is detached from said first respiratory gas source. Preferably, said means for supplying respiratory gases to a user includes means for covering the respiratory apertures of the user selected from a partial face mask, a complete face mask, a hood or a bag. In an embodiment of the invention, the means for enabling supply of a second respiratory gas source to said supply means comprises a filter arrangement. Desirably, the means for supplying a second respiratory gas source to said supply means comprises a reservoir for •containing respiratory gases and/or expired gases, so that said apparatus includes a rebreathing system and functions as a respirator or ventilator. Further preferably, said automatic switching means includes a release mechanism for rendering said absorption means operative when said supply means is detached from said first respiratory gas source. Alternatively, said automatic switching means comprises a seal/obturator means which renders the absorption means operative when the supply means is detached from said first respiratory gas source. The apparatus of the invention may include one or more of the following: a heat sink; an additional respiratory gas source; an additional C0 absorber; an additional filter; an additional reservoir; an additional release means; and an additional valve or valves. The reservoir may be enlarged to make a combined mother and young child unit. The apparatus of the invention may also include a ' logic circuit for controlling automatic delivery of apparatus, selection and supply of respiratory gases, broadcasting of instructions to passengers and providing an indication if apparatus has been tampered with or opened. According to an embodiment of the present invention there is provided breathing apparatus comprising a face mask attached to but detachable from an oxygen supply tube and connected to an inflatable reservoir or bag held in a deflated rolled up condition but releasable to provide when attached and deflated, an oxygen supply system and, when detached and inflated a portable respirator or ventilator in a closed rebreathing system with rebreathing bag and.oxygen supply in a microclimate free from noxious or -hot gases. The functions of the component parts of such apparatus are as follows: The face mask covers the nose and mouth, and may be extended to cover the eyes, and fits onto the face to provide a seal to prevent inward movement of noxious or hot gases whilst allowing outward movement of the exhaust gases when the rebreathing bag is rolled up. The self closing valve when held open by the oxygen supply tube allows the . passage of gases in both directions within the tube. When the oxygen supply tube is removed the valve is closed and does not allow the passage of gases in either direction. The carbon dioxide absorber absorbs carbon dioxide from the expired air. The reservoir may be rolled up and retained thus by a retain/release mechanism in one position or it may be freed and able to be inflated when the retain/release mechanism is in another position. When the reservoir bag is rolled up the equipment behaves as a simple oxygen delivery system. When the bag is released the equipment behaves as a closed rebreathing system. The retain/release mechanism may be used to retain the bag in a rolled up position or to release it from this position to allow it to be inflated either from the oxygen supply or with expired air. The guide means attached to the oxygen supply tube ensures that pulling the release mechanism first releases the bag reservoir. The mechanism is also designed to ensure that the bag is automatically released when the mask is disconnected from the oxygen supply. In practice, during an emergency face masks would be automatically delivered to all passengers, as presently happens on sudden cabin decompression. Each passenger puts a face mask in place and inhales oxygen through the oxygen supply tube. Exhaled air is voided to the cabin atmosphere and the lungs become filled with oxygen or oxygen enriched air. Thus the partial pressure of oxygen in the lungs is increased. This breathing of oxygen may be continued if necessary at normal atmospheric pressure for fifteen minutes or longer without side effects. When the passenger has to leave the aircraft cabin quickly a maximum inspiration is taken and the breath is held for a moment. The face mask is then supported with one hand while the oxygen supply tube is pulled out with the other and this automatically releases the rolled up reservoir. Alternatively the release"mechanism may be operated sequentially, firstly to release the inflatable reservoir and to inflate it with oxygen from the oxygen supply tube and secondly after a suitable interval to detach the oxygen supply tube. In either event exhaled air then passes through the carbon dioxide absorber and inflates or further inflates the reservoir which becomes ajrebreathing bag. Rebreathing could take place for several minutes without ill effect in the'absence of an absorber but the presence of this extends-the time for which rebreathing can take place without dangerous build up of carbon dioxide. Thus each passenger takes with him his own portable breathing apparatus with rebreathing system and oxygen supply in a microclimate at normal temperature, free from noxious or hot gases. If a passenger is unconscious the same apparatus can be used by a member of the cabin staff to secure his safe evacuation but with slightly different use. Firstly, the face mask is placed in position and held there by hand. Secondly, the bag release is operated without disconnecting the oxygen supply. Thirdly the reservoir is inflated with oxygen from the oxygen supply. Fourthly, the oxygen supply tube is .disconnected from the face mask. The unconscious * passenger now has his own portable oxygen supply and • rebreathing system. If necessary however, the apparatus can be used as a ventilator to inflate the lungs by manual compression of the reservoir while holding the face mask firmly in contact with the passenger's face. This invention also relates to improvements in passenger protection breathing apparatus including a seal mechanism which is not affected by change of cabin pressure, a co-axial circuit and valve arrangement to ensure efficient elimination of nitrogen with economical use of oxygen, means for switching the carbon dioxide absorber from the closed sealed storage mode to the open unsealed breathing mode, an improved harness for donning and adjustment and a modification for protection of infants and young children. There is automatic unsealing and the apparatus may be used by unskilled and untrained persons. The functions of the component parts of such apparatus are as follows :- The cover enables breathable gas to be carried to the respiratory apertures and carries expired gas to the carbon dioxide absorber. It may be a half mask covering nose and mouth, a full mask covering in addition eyes and face, a hood covering the head, or otherwise and it may be composed of rubber, plastic or other material. The self closing valve when held open by the oxygen supply tube allows the passage of gases in both directions within the tube. When the oxygen supply tube is removed the valve is closed and does not allow the passage of gases in either direction. The carbon dioxide absorber absorbs carbon dioxide from the expired air. It comprises a container, corrugated plastic tubing or otherwise, which holds absorbent material, soda lime or otherwise. The reservoir, a rubber bag or otherwise, holds breathable gas and functions both as an expansion chamber during the storage mode and also, during the breathing mode, as an oxygen collection chamber and rebreathing bag. The oxygen source is a source of breathing oxygen contained in a small pressure vessel, cylinder or otherwise, activated by a cord pull or other mechanism. This may be part of or attached to the release means. Additional or alternative sources may be provided from major fixed storage vessels from chemical generators or from other means. Where necessary a quick release means is provided to disconnect portable from fixed parts of the apparatus. The oxygen source is fixed to the conveyance means to prevent it from obstructing escape. The oxygen supply and delivery means comprising tubes, plastic or otherwise, conveys oxygen from the source and delivers it to the reservoir where it may be most efficiently used. Interposed between these two tubes is part of the seal mechanism described later. To avoid separate tubes which may become entangled one is placed inside the other in a co-axial arrangement. An exit valve spring loaded or otherwise, permits gas to escape from the cover to the exterior when pressure within the system rises above a determined amount, preset or otherwise. It must be sited in the cover close to the respiratory apertures to be most efficient. The seal means provides in essence an effective seal at one end of the container which holds the absorbent material. The main seal, rubber or otherwise, is attached to an obturator, plastic or otherwise, and these together occlude completely the lumen of the outer case, which is made of plastic or otherwise, when the mechanism is in the closed position. This effectively seals one end of the absorber container but the other end opens into the reservoir which is a closed system not open to the air and in which the absorbent material will keep for many months. Additional seals, rubber or otherwise, are provided near to the ends of the obturator to ensure that the obturator remains parallel to the outer case. The seal nearest to the oxygen source, called the pneumatic seal., also seals the oxygen supply tube so that the obturator is automatically moved to the open position by oxygen under pressure when the oxygen supply system is activated and the mid seal between the main and pneumatic seals prevents passage of oxygen directly into the mask. An external seal is required where the obturator expansion passes through the case. The switch on means comprises an obturator in which there is an aperture running from proximal to distal in the obturator. Movement of the obturator essentially switches the absorber from the closed storage mode to the open breathing mode. In the storage mode the obturator is close to the oxygen supply tube and the main seal is in the closed position with the obturator aperture on the absorber side of the seal. The obturator cannot move beyond this position because there is an expansion of the obturator at the other end which is prevented by the outside of the outer case from moving further. This expansion, plastic or otherwise, also serves as a handle to move the obturator manually, and to indicate its position. In the breathing mode the obturator is at the opposite end of the outer case prevented from moving further by the end wall of the case, the seal is broken and the aperture is in line with the channels to mask and absorber so that gases can pass freely to and fro. Thus the conversion means switches the absorber means from the closed storage mode, in which the absorber means is sealed and unavailable for use, to the open breathing mode in which the absorber is unsealed and available for use. Alternatively the obturator may be moved by a coiled up spring or otherwise between the expanded end of the handle and the outer side of the outer case. The spring may be held in the coiled up position by the wall of the box or container of the breathing apparatus so that it is automatically released when the apparatus is removed from the box. Thus each passenger takes with him his own portable breathing apparatus with rebreathing system and oxygen supply in a microclimate at breathable temperature, free from noxious or hot gases. If a passenger is unconscious the same apparatus can be used by a member of the cabin staff as a ventilator to inflate the lungs by manual compression of the reservoir while holding the face mask firmly in contact with the passenger's face. Since the apparatus is for use in fire and smoke it should be resistant to chemical substances found there and to high temperature. The donning means, comprising a strap or straps rubber or otherwise, is used to don the mask, or hood, and to adjust the fit of the mask on the face. The donning straps are held and are used to pull on the mask. The same straps are then pulled through the buckles to tighten the fit on the face but the ends may be difficult to find. This is avoided if each strap is continuous in a figure of eight loop for the strap to be tightened is the same as that used for donning. The passenger protection breathing apparatus may be used as a hood, plastic or otherwise, with a neck seal, plastic or otherwise, for older children. In such a system the dead space is greater and relatively more oxygen will be required to flush out nitrogen. The adult passenger protection breathing apparatus may be modified for babies and small children by attaching a large bag, plastic or .otherwise instead of the reservoir. The distal end is sealed in the storage mode but has a means to facilitate tearing it open. It also has a draw string about the middle. A baby is placed completely inside the bag and the end of the bag is folded over severaltimes * and held closed with strong spring clips. Alternatively it is placed over the head and body of a small child and the draw string is pulled tight around the abdomen for closure. In the meantime the mother or other parent has-donned her face mask and there is now a dual tandem system in which the mother circulates her expired gases through the absorber. Since the large rebreathing bag may initially be filled with air a larger amount of oxygen will be required to flush out nitrogen. It. will be noted that the passenger has only to put on the mask, tighten the straps and breathe normally. The high pressure in the oxygen source ensures that the oxygen flow rate is considerably in excess of uptake. Thus more oxygen is entering the bag than is being removed by the lungs and there is an oxygen gradient from bag to lungs. When the bag is full, nitrogen rich gas is exhausted from the system and oxygen levels will approach 1009. in a few minutes. Relevant anaesthetic principles are described in a synopsis of anaesthesia by Atkinson et al 1984. Wright, Bristol. The circuit described is similar to a Magill circuit but uses coaxial flow. However this is different from the Bain and Lack circuits and involves an inventive step to meet the needs of aircraft passengers using a rebreathing system and carbon dioxide absorber while breathing spontaneously and not under anaesthesia. Obviously improvements and adaptation of the described system may be made for use by experienced staff and changes may be made for ease of maintenance. The oxygen supply may be controlled by a manually operated valve for nitrogen washout or otherwise and an "on demand" system may be incorporated for use during exercise. Soda lime,, or other absorbent agents may be used and indicators which change colour when the agent is exhausted may be used to confirm at the time of maintenance that the absorbent is active. - Ik - The present invention mill be further illustrated, by ωay of example, ωith reference to the accompanying drawings, in ωhich: Fig.1 shαωs in perspective and cross section the breathing apparatus ωith the oxygen supply tube attached and the reservoir retained in the deflated rolled up pαsitiαπ by the retain/release mechanism; Fig. 2 shαωs in perspective and cross section the breathing apparatus ωith the αxygeπ supply tube detached and the reservoir released in the inflated pαsitiαπ ωith the retain/ release mechanism still attached tα the oxygen supply tube; Fig. 3 schematically shαωs the inclusion of an additional reservoir tα compensate for the intermittent nature of breathing of a user; Fig. schematically shoωs the use of a combined face mask and hααd arrangement in the inoperative position; Fig.5 schematically shoωs the face mask and hood arrangement of Fig.4 in the operative position; Fig. 6 schematically illustrates a modified system of the embodiment illustrated in Figs. 1 and 2. Fig. 7 diagrammatically illustrates a linear type arrangement of an embodiment in accordance ωith the invention; Fig. 8 diagrammatically illustrates the system of . Fig. 7 but ωith the oxygen supply tube removed; Fig. 9 is an electronic circuit for use in accordance ωith the present invention; Fig. 10 is a schematic vieω αf an alternative embodiment in accordance ωith the inventiαπ utilising a proximal seal assembly, coaxial oxygen supply tube and carbon dioxide absorber; Fig. 11 diagrammatically illustrates a complete filter assembly and receptacle means ωhich may be utilised in association ωith the device of the present invention; Fig. 12 shαωs a mother and baby unit; Fig. 13 diagrammatically illustrates a hood arrangement in the inoperative pαsitiαπ; Fig.14 diagrammaticaly illustrates the hαod arrangement of Fig.13 in the operative position; and Fig. 15 diagrammatically illustrates a modification αf the apparatus of Fig. 1 in ωhich the reservoir is replaced by a filter. As illustrated in the embodiment shoωπ in Figs. 1 and 2, the breathing apparatus comprises a face mask 1, made for example from plastic or rubber, connected by ωay of a self closing valve 2, made for example αf opposing rubber flaps, tα an oxygen supply tube 3, ωhether plastic αr αtherωise, and by ωay αf a carbon dioxide absorber 4, ωhether chemical using sαda lime αr αtherωise, tα a railed up reservoir 5, ωhether an inflatable rubber bag αr otherwise, ωith a manual release mechanism 6, ωhether a single cord tied tα a rubber band or otherωisε, led through a guide means 7, ωhether a metal ring or otherωise and connected to the oxygen supply tube 3, cord 6A being connected to the reservoir 5. In Fig. 1 the breathing apparatus is shoωπ attached to the oxygen supply tube 3, and in Fig. 2 the breathing apparatus is shoωπ detached. In particular it should be noted in Fig. 2 that the oxygen supply tube 3 is detached, that the valve 2 is closed, that the manual release mechanism 6 and the cord 6A are still connected to the oxygen supply tube 3 but not to the reservoir 5 ωhich is nαω inflated. In order to detach the oxygen supply tube 3, the face mask 1 is held and the oxygen supply tube 3 is pulled out αf the self closing valve 2. The same movement will pull the cord 6A attached tα the oxygen supply tube 3 and will automatically release the rolled up reservoir 5 retained by the cord 6A αf the release mechanism 6. If desired, the rolled up reservoir 5 can be released for inflation ωith oxygen via the oxygen supply tube 3 and via the carbon dioxide absorber 4 by manually pulling the release mechanism 6 through the guide means 7 aωay from the rolled up reservoir 5 ωithαut pulling the oxygen supply tube 3 out αf the self closing valve 2. Whilst a face mask has been utilised in Figs. 1 and 2 tα envelope the respiratory apertures, it is also possible to envelope the ωhαle head or body utilising for example, a bag;or hααd. Clearly it would be advantageous if the material used tα envelope the respiratory apertures or indeed the entire apparatus is fire resistant. The volume of the envelope should be large enough for normal breathing ωhen used as an oxygen supply system and might itself be expansible and contractible as is a bag or hood. Whilst the floω of oxygen through tube 3 is constant, respiratory breathing is of an intermittent flαω nature. Accordingly tα compensate far such situation as shown in Fig. 3, an additional reservoir 9 can be added-and could for example be placed adjacent tα the mask and connected by a side arm 8 tα the oxygen supply tube 3. A one ωay valve 10 between the side arm and the mask would prevent rebreathing into bag 9. Expired air passes along side arm 11 and is vented to the exterior through an additional απe ωay valve 12. The supply tube 3 is connected to a supply source of respiratory gases comprising oxygen either as pure oxygen or air. The choice of gas ωould be made by the aircreω αr cabin staff. The oxygen might be generated chemically or stored under pressure in containers designed for the purpose and ωith suitable pressure regulation means associated therewith. Such a supply source might serve - a plurality of outlets. Air might be similarly stored αr obtained from another source free from noxious or hat gases. The valve 2 may be a simple valve to allow free passage αf respiratory gases when open and to allow no passage of gases in either direction when closed. Hoωεver, this αr another more complex valve might be used to regulate the gas flαω ωith reduction from source pressure tα delivery pressure. The supply tube might be rεcoππectable as ωell as discαπnectablε. Rεcoπnεctioπ may be achieved for example simply by pushing the supply tube 3 through the valve 2, for example a valve made from opposed flaps of rubber or αtherωise thick at the base and thin at the free edge to preserve the ability tα direct flαω. Whilst valve 2, when closed, prevents admission αf noxious αr hat gases into said supply means it can operate as an exit valve by removal αf the second element αf the valve tα permit escape of expired air into the atmospherε. Thε absorber 4 and reservoir 5 are excluded from the breathing circuit when used as an oxygen supply system but both are included in the circuit ωheπ used as a portable respirator or ventilator. In thε embodiment using a hααd αr a bag, there is an εnlargεd cover 1. In a hααd, respiratory action ωould probably be sufficient to circulate expired air but if παt, as in the bag for an infant, a manually operated bεllows could be usεd. Thε αxygeπ supply system utilised in Figs.4 and 5 is that illustrated in Fig. 3. Thε face mask 1 is part of the wall αf the hααd at thε dome, or possibly elsewherε, with thε αxygεπ supply tubε 3 at the apex. Thε dαmε is fixed tα the face mask and thε hααd is fαldεd like a concertina with a neck sεal 13 fittεd round thε facε mask tα kεep the hood interior sealed and therefore to kεεp thε 10 carbon diαxidε absorber 4, ωhich is spread out on the inside αf thε hααd, sωitchεd out of the circuit. When usεd as an oxygεπ supply system for decomprεssiαn or, as an air supply systε far in flight firεs, the face mask 1 is used. Additional valves may be provided tα prevent back Tc floω αr tα allαω voiding to the external at αsphεrε and a collecting bag may also be provided. For escapε, the hood is pulled over the head, using thε handlεs 14 provided, and the oxygen supply tube 3 is pulled out. A release means 6A, attached tα the tube 3 and tα an integral oxygεπ 2Q cylinder 15 automatically sωitches on thε oxygεπ supply from source 15. In a relatively large volume hood or envelope there is no separata rεbrεathiπg bag. The absorber is dispersed on and fixed tα the inside surface αf the hood. It is covered by a seal ωhich is pεεlεd back tα εxpαsε the 25 absorber ωheπ it is switched in to thε circuit. Hαωever, it is important to have a smaller volume hoαd for airflαω and a larger volume for escapε ωhεπ pure oxygen is used. For escapε thε αxygεn sourcε is activatεd at thε samε time.as thε absαrbεr is sωitched in to the circuit. In a completely self contaiπεd 3 Q systεm a sεparatε oxygen supply and separate absorber might be used ωith a pure αxygeπ supply system for decompression. For in flight fires air floω is requirεd ωith no absαrbεr but it dαεs not matter if an absorber is pressπt provided that ' there is a sufficiently high air floω rate and that another 2 absorber is availabls to bε switchεd in for εscape. A securing mεans ' such as a head harness or body harness, may be used tα secure the face mask, hood or bag. The hood may be secured under a jacket or round the neck by an elastic grαmmet, that is polo neck or turtle neck, or by αthεr means. Thε bag may be closed by a draw string or otherwisε. Additional eye protection means may be an εyε shield or gaggles with a face mask or may be a transparent hood or bag or with a clear window αr visσr in it. Other additions might include an ancillary portable oxygen or air supply, such as a small pressure cylinder which might also be activated by the same release means using a third cord. A separate release means could be used and ωould make the device more complex and difficult tα use but this cαuld be overcome by incorporating a time lapse sωitch to release the oxygεπ frαm the sparklet αr a series of sparklets at fixed αr presetable time intervals. A circulation means may comprise an additional system of one ωay valves and/σr circuits tα ensure passage αf expired air through the absorption means. This additional system may be inside the mask or hααd and may include a projection attached tα one ωall αf the mask or hαod tα be an additional sεcuring means ωheπ gripped by the teeth. The essence of the invention is a means αf sωitching the absorption means out αf or in tα the breathing circuit. This may be dαπe in other ways so that thε samε rεsεrvoir may be used far rebreathing and far collecting.- This system, shoωπ for example in Fig. 6 consists αf an arrangement in line αf oxygen supply tube 3; self-closing valve 2, common reservoir 61 C0„ absorber 4, additional valve 62 and face mask 1. The additional valve 62 alloωs gases to pass in tα the face mask but not out. This system may be convεrtεd to a rεspirator if a rεlεase cord 6A attached to the guide ring 7 remαvεs αr holds open the valve 62 or opens a bypass which bypasses it. Thε bypass may far examplε be a collapsible rubber tube retained in a folded and closed condition by an εlastic band attachεd by thε card and guidε ring 7 tα thε supply tubε 3. When the supply tubε 3 is rεmoved the elastic band is pulled off to rεlεasε the bypass to thε opεn condition. It will be appreciated by thoseskilled in the art that the diagrams illustrate priπciplεs ωhich must bε implemented in accαrdaπcε ωith well established kπαωledgε dεscribed for example in R.S.. Atkinson et al 1982, a synopsis of anaesthesia, Wright, Bristol. It will also be clear that the same result may be achieved in other ωays. For example Fig. 7 shαωs in diagrammatic farm a linear arrangement αf oxygen supply tube.3, valve 2, dual purpose bag 71, absαrbεr 4, and mask 1. One ωay valves ωith air flαω direction indicated by arrαωs .._ arε placεd in thε mask inlet circuit 16 and in the rebreathing circuit 17 near the mask. The circuit 17 is occluded by an extension of the supply tube 18. Incoming air or oxygen enters thε bag through holεs 19 in thε tube ωhich has a fusiform enlargement 20 tα prevent it slipping out. Expired air is veπtεd to the cabin round the side of.the mask. Tα facilitate reinsertion, a guidε means 21 may be provided far example from metal rods fixed at each end. Whεπ, as in Fig. 8, thε αxygeπ supply tube 3 is removεd together ωith its extension 18, the rεbrεathiπg circuit 17 is no lαπgεr αccludεd. The apparatus is παω a rebreathing system ωith gas flαω from bag 71 by ωay αf inlet circuit 16 to mask 1 and by ωay αf rebreathing circuit 17 back tα bag 71. It is obviαus to those skilled in the art that improvements may be made. For example the chamber 71 in Figs. .7 and 8 may become a small junction chamber more simple to manufacture and the rebrεathiπg bag may be connectεd tα thε surfacε B (Fig. .8). Thε inlet breathing circuit 16 and rebreathing circuit 17 may bε concentric in crass section.ωith thε absorber 4 centrally placεd so that the extεπsiαπ 18 may be conveniently inserted. Additional valves may be inserted and circuit 16 may be closed during rebrεathiπg tα ensure double passage of gases through absorber 4 during inspiration and expiration. As previously mεπtioπεd thε respiratory gases comprise αxygeπ εither as pure oxygen αr as air and the choice αf gas ωαuld be made by thε aircrεω on the flight deck or by the cabin staff. An embodiment for automatic selection of gas or of gas mixture to coπservε αxygεn and in particular that stored under pressure for such pressurised oxygen is itself a fire hazard if thε delivery or storage system is peπεtratεd by the fire described with reference to Fig. 9. An electronic circuit is shoωπ containing logic gates ωhich are ωell known in the art. A logic gate having the function OR gives an output signal ωheπ there is an input signal in απe input line OR in any other input line from a plurality of such inputs. A logic gate having the function AND gives an output signal when thεre is an input signal in απe input line AND in all other input lines from a plurality of such inputs". Λ logic gate having the function NOT changes the signal state αf input and output. Thus, there is NOT an output signal when there is an input signal and vice versa. An embodiment αf the logic circuit required for automatic delivery αf apparatus and respiratory gases to aircraft'passengεrs is shown in Fig. 9. It is well ' known in the art that additional devicεs all well kπoωn in ths art are required far operation of said logic circuit. The plurality αf additions not shown in the diagram include a power supply means, circuit closing means, for example a manually operated switch, and signal geπεratiπg mεans. • All input circuits 24-29 arε connected to a plurality αf alarm sωitches or detectors each αf ωhich generates a signal in the appropriate input circuits ωhen operated manually or automatically tα give ωarniπg of in flight condition. Such warning might include an indicator means, visual or auditory or other, tα indicate that the recεptacle means has beεπ opεπεd and thus detεct, in an εmεrgεπcy, that all passengers are using, or attempting to use, breathing apparatus and, in the absence αf an emεrgency, that someαπε is tampεriπg ωith passεπgεr protεctiαπ apparatus. Such manual sωitchss arε distributed at convenient sites in the aircraft to be operated by flight deck or cabin staff. 5uch automatic detεctors are also conveniently distributed far exercise of detection function. All output circuits 30-33 are connected tα mechanical or elεctrical dεvicεs, ωhεthεr valves αr αthεrωisε, to prεsεnt brεathiπg apparatus ' to passεngεrs and to deliver in said oxygen supply tubε appropriate gases αr mixturε of gasεs. Thε logical control dεcisiαns arε madε by logic gatεs 34-40 having inputs frαm input circuits and/or othar logic gatεs and having outputs coππεctεd tα αthεr logic gates and/or output circuits. Warning αf an in-flight fire is given manually by pressurε on switch αr automatically by smαkε dεtεctiαπ mεaπs or othεrωisε to generate a signal in circuit 24. Warning of emεrgεπcy αr prεcautiαπary landing is givεn by similar manual switch αr αthεrwisε tα generate a signal in circuit 25. Warning αf abort αf take off similarly gives a signal in circuit 26. Cabin pressurε may be detεctεd by prεssurε sensors in the cabin or otherwise and a signal is generated in circuit 27 ωhen said pressure is lαω and in circuit 2B ωheπ said pressure is normal. Outlet demand may be detεcted by breaking αf a circuit ωheπ the bαx is αpεπed αr by pressurε detectors in oxygen supply tube, compared if necessary with cabin pressure, tα detect lowered prεssurε resulting from inspiration αr otherwise and a signal is generated in circuit 29 ωheπ said demand is detεctεd. Thε purposε αf supply, only on demand-, is to rεducε loss of oxygen ωhich may fuel a fire. Thε OR gate 34 has four inputs connected to circulate 24, 25, 26 and 27 and an output to secure release αf breathing apparatus to passengers in any αf the εveπts recognised in said circuits 24 tα 27. The OR gate 35 has three inputs cαππectεd to circuits 25, 26 and 27 and an output tα AND gate 36-. This has a corresponding input, an other input from circuit 29 and an output 31 to secure delivery of pure αxygeπ tα passengers in the event αf outlet demand AND one αf thε events signalled απ circuits 25 tα 27. The AND gatε 37 has three inputs connected tα circuits 24, 28 and 29 and output 32 is given to securε delivery αf pure air to passengers. The AND gate 40 has an input from the output αf NOT gate 36 the input of ωhich is connected to circuit 28 such that AND gate 40 recεivεs an input signal if input circuit 2B is NOT indicativε αf normal cabin pressure. A similar circuit through NOT gate 39 to input circuit 17 is such that AND gate 40 receives an input signal if input circuit 27 is not indicative of low cabin prεssurε. Thε third input to AND gate 40 is connected tα the input circuit 29. Thus thε output circuit 33 is activatεd if there is a signal on all thrεε inputs αf gatε 40 to secure delivεry αf a mixturε of αxygεπ and air. It is obvious to thosε skilldd in thε art that anothεr typε of logic gate, for example NAND and NOR, may be used and that other types of device, for example fluid logic devices, may be usεd. It is also obvious that diffεrent pressure ranges, othεr than normal or law, may be recαgπisεd and that the proportion αf air and oxygen may be adjusted accordingly, that is regulation αf gases bath in respect of quantity and quality. It is also obvious that detεctiαπ αf an εxcεssive demand may indicate penεtration αf a supply line by fire with lass of gas and that in such event the corresponding supply sources should be shut off. " It is also obvious to those skilled in thε art that other devices such as microprocessors may be used and have advaπtagεs including ease αf handling a multiplicity of signals, ability to deal ωith complεxity and εasε of rε-programmiπg in the light αf expεrieπcε. Rεfεrriπg to Fig. 10 thε mαdifiεd brεathiπg apparatus comprisεs facε mask 1, self closing valve 2, exit valve 2A, oxygεπ supply tube 3, carbon dioxide absorber 4, inflatable reservoir 5, oxygen sourcε 15, sεal assεmbly 22 haπdlε and indicator 23 and αxygeπ delivεry tube 3A. A rεleasε card A is associated ωith oxygen source 15 tα automatically cαmmεπcε αpεratiαn thεrεαf ωhεn thε αxygeπ supply pipε 3 is pullεd out αf valvε 2. It should bε παtεd that εxit valvε 2A is in an altεrnative position tα exit valve 12 in Fig. 3. Furthermore, as has bεεn nαtεd, valvε 2 may bε an εxit valvε. Thε sεal assεmbly may be operated tα permit the rebreathing cycle to be eπtεrεd. The device is held firmly against the apparatus container wall. In such arrangement, it is clεar that the auxilliary devicε is not brought into αpεratioπ. When thε dεvicε has been remαvεd from thε apparatus contaiπεr wall the indicator 23 is allowed to move and a frεε passagε αf αxygεπ is pαssiblε betweεπ mask 1 and rεservαir 5. The seal mechanism includes an obturator and a number of channels. When the αxygeπ is switched απ the prεssure of the oxygen pushes the αbturatαr along until the opening is in line ωith the channels to the resεrvoir and mask. Thε end αf the ■ cαπtaiπεr ωall prevents further movement. At this point, the end πearεst to the αxygeπ sourcε has mαvεd beyond the oxygεπ supply tube and αxygeπ flαωs down this tα the reservoir. The seals prεvεπt lεakagε of αxygeπ αr movement αf gases except wherε intended. In Fig-. : 10 the exit valvε 2A is an alternative to 12 in Fig. 3. It should have an adjustable pressurε sεttiπg with resistance set tα be higher that the maximum pressure rεquirεd far rebreathing but loω enough tα allαω voiding to..external atmαsphεrε, ωheπ the system is full,to prevent lung damage from too high pressure due, for example, from malfunction αf pressurised oxygen supply sourcε. As previously mentioned the respiratory gases comprise oxygen either as pure αxygeπ αr as air and the choice of gas ωould bε madε by aircrεω in the flight deck or by cabin staff. It should παω be made clear that an alternative oxygen supply sourcε includεs purε oxygεπ from a chemical generator or stored αxygεπ and it also includes αxygεπ in air. Furthermorε the air supply source may be ram air or bleed air or compressed air or filtered air. Filtεrεd air will not protεct against hot gases but filters can provide substantial protection until exhausted, until the air becomes tαo hot tα breathe αr until it is time tα escape. However, a filter system ωith a heat sink added, may provide adequate protection against hot gases and may bε prεfεrred if it has other advantages, for example lightness αf weight. A 500 gram ilter may, depending upon smoke density and other factors, provide protection for 20 tα 30 minutes and may be suitable for some in flight fires. It is an advantage that filters may be fitted without major engineering alterations tα the aircraft. Additionally thε filtεr should, like the carbon-dioxide absorber, be sealed and a method αf doing this is illustrated in Fig. 11. The cover 1 has a said self closing valvε 2 and αxygeπ supply tube 3 passes therethrough. The proximal end αf said αxygeπ supply tube 3 is sealed by a proximal seal means 41 attached by a proximal cord mεaπs 42 tα a rεcεptaclε means 43 or box or otherwise fixed tα thε aircraft. Thε distal and αf said oxygen supply tubε 3 is conπεctεd to or becomes the proximal end of a filtεr means 44 and a distal seal mεaπs 45 sεals the distal αr air intake and of thε filtεr and is conπεcted by thε distal cord means 46 tα the recεptacle means 43 αr αtherwisε fixed. Thus removal of the mask and filtεr frαm thε box automatically uπsεals the filter 44 and proximal end αf said oxygen supply tube 3, by rεmoviπg the seals 41 and 45. The filtεr 44 is alsα fixsd tα the recεptaclε mεans 43 by an additional cord mεans 47. This allows thε filterεd air systεm to be used by a seated passenger but it automatically sεparatεs thε filtεr 44 and oxygεπ supply tube 3 from the cover 1 and self closing valve 2 ωheπ thε passεπgεr lεavεs his sεat to escape from the aircraft. Thε said third cord tα activatε thε stored oxygen sourcε may also bε attachεd tα said filtεr 44 tα ensure that said source is activatεd automatically at thε timε of εscapε. Thε said filtεr must bε capablε of rεmoviπg smoke particles, carbαπ monoxide gas, cyanide as and other toxic substances. The combination of a filterεd air course ωith a pure oxygεπ rεbrεathiπg systεm may bε dεscribed as a hybrid systεm. Thε dεvicε αf Fig.- 11 alsα includes, but παt shαωπ, an exit valve and a release mechanism tα bring the rebrεathiπg bag into operation. The functions of the component parts αf the apparatus are as follαωs. The cover, the self-closing valve and the oxygen supply tube are as previously described. The proximal seal means seals the proximal end of thε " αxygεπ supply tubε. Thε proximal cord means attaches the proximal seal means to the receptacle means. The receptacle means holds the apparatus and is itself firmly fixed tα the aircraft. The filter means is the distal part αf the αxygeπ supply tube and contains substances ωhich removε by filtration παxiαus gasss. The distal seal means seals the distal αr air intake end of the filter means. The distal cord means attaches the distal seal mεaπs to the receptacle means. The additional card means attaches the filter means to the recεptacle means and thε cord is long enough for the apparatus to be removed from the box and used by a seated passenger. The filter may be remote and may serve several passengers. It may have a long connecting tube (not short as shown) which may have an exit valve 12 as in Fig. 4 and/or collecting bag 9 and παπ-rεturπ valve 10. Such might be used with a αtαrised filtεr systεm. Thε modified rεsεrvoir in thε αthεr and baby unit (Fig. 12) is clαsεd by folding aver the end and holding it closed with spring clips 48, and in the mother and young child unit it is closed by a drawstring 49 round the abdomen. In the sealed mode.of a hood εmbodimεπt as shown in Fig. 13, the self closing valve 2 and oxygen supply tube 3 are cαππectεd to the cover means 1, which in turn is coππεctεd to thε hood. Thε hood is foldεd in thε horizontal plaπε so that thε absorbεr 4 is in a fold and thε rεservαir 5 is εmpty. Thε fold is kεpt in pαsitiαπ by a sεriεs of radially pαsitioπεd guidε means 7 and by two relεasε mεans 6A. An additional release means is rεquirεd to activatε thε oxygen supply sourcε 15. Each ring αf thε guidε mεans is in a vεrtical plaπε with altεrnatε rings attachεd tα uppεr and lσωεr εdgεs αf thε fold. Each rεlεasε mεaπs is attachεd at onε επd to thε oxygen supply tube 3 and is thrεadεd through thε ipsilatεral sat αf rings tα kεep the absorbεr 4 sωitchεd out αf contact ωith thε iπspirεd and εxpirεd gasεs. Thε absorber is shoωn in Fig. 14 in the open circuit state. Tα sωitch the absorber in tα the circuit the αxygεπ supply tube 3 is ωithdraώπ and automatically pulls out bath releasε mεaπs 6A. Thε αpposεd surfacεs αf the absorber 4 are no longer held togεthεr by thε guidε means 7 and the fold is unfolded by the pressurε of oxygεπ to expose the absαrber 4 in thε covεr mεaπs 1 and rεsεrvoir 5 ωhich arε now combined as one επlargεd hood. A sεparate releasε means may be provided tα switch in the absαrber without pulling out the oxygen supply tube 3. It is αbviαus tα those skilled in the art that the fold in the hααd may, alternatively or additionally, be in a vertical plane, corαπal, sagital or other. A coronal fold would not obstruct vision and any vertical fold would decrεasε hααd volumε. Also thε dαmε may bε silvεrεd to reflεct hεat. Thε oxygεn supply tubε 3, shown as sited low down, may be sited in the dome or εlsεwhere and the diagram is shown by way αf examplέ only. As in thε facε mask model one αr more portable oxygen supply sources may be attached to the hααd, far examplε a first purε αxygεn sourcε and a first absαrber for dεcomprεssiαπ, a high floω air supply source for in flight fire and a sεcαnd pure oxygen sourcε and sεcαπd absorbsr for εscapε. The εmbodimεnt αf Fig. 15 is similar tα that of Fig.l, but in which thε rεservoir 5 has been replaced by a filter 50. The releasε mεaπs 6 and 6A unsεal the filter 50 (in the manner as shown in Fig. 11). In this embodiment, an exit valve 2A is shoωπ and therε arε tωα entrance valves. Thε first valvε 2B is adjacεπt thε carbon diαxidε absαrbsr 4 and thε sεcαnd valvε is in thε αxygεπ supply tubε 3 (as prεviαusly described in Fig. 3 as valve 10). It should bε noted that the opening pressures αf valves 2B and 10 should be balanced such that valve 10 opεπs first and valvε 2B does not opεπ until no furthεr gas can be obtained through valve 10, or through αxygeπ supply tube 3 at the site αf valve 10; thus valve 2B ωill automatically open to supplement breathable gas ωheπ required if manual release 6 has been activated. The filtεr sεal is rεquired far the purpose of excluding air from the filter 50 during thε stαragε modε. It ωill bε apparεnt tα thosε skillεd in thε art that changes may be made in the shape, design and material composition αf thε apparatus and that a variεty αf manufacture methods, of types, αf sizes and of devices may be used for the components thereof; face mask, oxygen supply tube, self closing valvε, carbon diαxidε absorbεr, rεtaiπ/rεleass mechanism, guide means and inflatablε rebreathing bag resεrvαir. It ωill also bε apparεπt tα those skilled in the art that additional αr ' aπcilliary apparatus may be used including ' means αf ensuring a ωell fitting face mask, including a head harness to hold the face mask in position, including goggles tα protect the eyεs from noxious gasεs and very hot air, and including an additional system αf απe ωay valves and/or circuits tα sπsure circulation, to αr frα, of air from lungs to absorber, tα resεrvαir and back to lungs. It ωill also bε obvious to thosε skillεd in thε art that thε apparatus illustratεd, the methods suggεstεd and thε possibility far aπcilliary apparatus arε givεπ by ωay αf εxample only and dα not exlude thε many othar mεthαds or possibilitiεs ωhich arε obvious for such brεathing apparatus or ancilliary apparatus. Oπε furthεr example may be given becauss αf its simplicity and suitability for childrεn of diffεrεπt sizes and ages and particularly for yαuπg children. In essεπcε it is a largε clεar plastic bag connected tα the oxygen supply tubε"through a sεlf closing valve. Thε bag is placεd ovεr thε head and shoulders and a seal is provided by putting on a pullover, anorak or jacket fastened up to the neck απ top of the bag. The bag is inflated ωith αxygeπ and the oxygεπ and the oxygen supply tubε is rεmovεd just bεfαre the child ωalks or is carried from the cabin αf the aircraft. It ωill be appreciated that the priπciplε is thε same but the entirε hεad is iπsidε thε rεbrεathing bag and-a carbon diαxidε absαrber may not bε nεcεssary due tα the rεlativεly large volume, αf the microeπvirαπmεπt cαmparεd with thε lung volumε and the rεlativεly short ti ε for which it is rεquired. Alternativεly a yαuπg infant could bε placεd εntirεly iπsidε the bag which cαuld be closed at the distal end opposite tα the αxygeπ outlet. However, it is safer to have an oxygen supply and carbon dioxide absorber as shαωπ in the mother and baby unit. The absorption αf carbon diαxidε is. an εxαthεr ic reaction and it is obvious that it may be necessary to coal the gas coming out αf thε absαrbεr αr to dispεrsε the heat or both. Coaling may bε pεrformεd by chεmical, physical or αthεr mεans, far εxamplε by combining it ωith an επdothεrmic rεaction. Dispεrsioπ may be achisvεd by using a hεat sink, far εxamplε contact ωith coppεr mesh or other goad heat conductor, or by a circuit arrangement, far examplε siπglε pass through thε absorbεr from lungs tα rεsεrvoir and rεturn αf mixεd gasεs ωhich bypass the absorber. The body is an efficient hεat sink bεcause the latent heat αf vapourisation of ωater is high and εxpirεd air contains much ωater vapour. It is obvious that removal of ωatεr vapour by a hygroscopic or deliquescεnt agεπt or αthεrωisε ωill εnsure the continued efficiency αf this heat sink mechanism. In any aircraft system ωeight ϊs of paramount impαrtancε and if, for εxample, a filter system ωith a heat sink is found tα provide adεquatε protεctiσn against hot gasεs but is lightεr than, for εxamplε, a closed rebreathing system then this ωαuld be preferred. Breathing apparatus may best be stored overhead and presented to passengers ωheπ required but this requires engineering modifications to aircraft. In the meantime, far apparatus fitted in tα a seat back, an indication may be given ωhen the container is opened. This ωill alert cabin staff to unauthorised use by children or others tampering, pilfering or attempting tα don hoods for other than emergency use. For example a circuit may be broken ωheπ a lid is lifted and an indication given at a crεω station. Thε rεbreathiπg bag may be the floatation chamber αf a life jacket so that both life support systems, smoke protection and floatation, are combiπεd. It ωill also bε apparent to thαse skilled in the art that such apparatus may bε usεd in an industrial environment and in hotel, shop, office and house fires and may be used by firemen, miners, sεωage ωαrkers, civilians and αthεrs ' and that additional αranciiliary apparatus may be usεd including means ωhether automatic or αtherωise of delivεriπg thε apparatus to passεngers ωhεn πεεded, including mεaπs αf issuing instructions during thε εmergeπcy, ωhεthεr by automatic rεcordεd mεssagε αr αthεrwisε, including indicator means, including means of inflating the reservoir directly frαm a fixed αxygeπ supply and including adaptation for usε with closεd αxygεn αr air supply systems as well as closed rebreathing systems. It ill.be obvious to those skilled in thε art that thε apparatus illustratεd, thε mεthods suggested and the possibility for ancillary apparatus arε given by way αf examplε only and do not exclude the many • other methods αr possibilities ωhich are obvious for such brεathiπg apparatus or aπcilliary apparatus. Of thε many obvious places for use of such brεathiπg apparatus hotεls and multi-stαrey buildings for offices and shops or stores should be mεπtiαπεd. ery similar, apparatus could be kεpt in each roam ωith a plurality αf outlets frαm an oxygen cylinder supplying sevεral rooms or a complete floor. Fire alarms could bε liπkεd tα rεcorded instructions for using the apparatus. If the apparatus is removed from its storage place an elεctrical signal could bε automatically traπsmittεd to rεceptiαπ tα indicate ωhich items mere bεiπg utilisεd. In hαtεl fires a longer time might bε πεeded to εscape and aπcilliaryapparatus such as oxygen sparklεt or sεveral such activatεd automatically at set time intervals or manually might be useful. Such apparatus might also be useful in industry in hostile environments to comply ωith Section 30 of the Factories Act 1961 and in mines and seωers ωhere εthaπε may cαllεct. It is alsα obvious that the apparatus may be used in coπvεrsε sεqueπcε that is coπvεrsiαn from portable breathing apparatus, used for example in rescuing people from house αr hotel fireβ or mines or seωers, to an oxygen supply system, when the sama apparatus is connected tα a βtatic oxygen aource, απcs the victim hαa been removed frαm the hostile environment. The addition of a small portable oxygen source mould be particularly suitable for this use. The apparatus may be used by firemen and by members of the armed forces during fires in aircraft, ships or buildings and by others. It ωill also be obviouB that in the case of the armad forces the conversion may be from portable gas mask using filtration means tσ portable respirator using rebreathing bag ωith icrαeπvironment and ωith further conversion option to static supply system. It is, of course, passible to utilise the rebreathing Bystem aa the first oxygen supply system in the case of decompression and/or in flight fire and tα switch to the filter system for escape from the aircraft.

Claims: CLAIMS 1. Breathing apparatus for aircraft passengers and others comprising: a) means for supplying respiratory gases to a user, said supply means being detachably connectable to a first respiratory gas source, and thereby constituting a first oxygen supply system, said supply means including valve means, which valve means, when said supply means is detached from the first respiratory gas source, automatically closes and prevents admission of noxious or hot gases into said supply means, b) means for supplying or enabling supply of a second respiratory gas source to said supply means, and constituting a second oxygen supply system, in which an absorption means for absorbing carbon dioxide is included; and either c) means for automatically switching from said first oxygen supply system to said second oxygen supply system when said supply means is detached from said first respiratory gas source; or c 1 ) means for manually or automatically causing said second oxygen supply system to become operative to -supplement or replace said first oxygen supply system, said second oxygen supply system continuing to be operable when said supply means is detached from said first respiratory gas source. 2. Breathing apparatus as claimed in claim 1, wherein said means for supplying respiratory gases to a user includes means for covering the respiratory apertures of the user selected from a partial face mask, a complete face mask, a hood or a bag. 3. Breathing apparatus as claimed in claim 1 or 2, in which the means for enabling supply of a second respiratory gas source to said supply means comprises a filter arrangement. 4. Breathing apparatus as claimed in any one of claims 1, 2 or 3, in which the means for supplying a second respiratory gas source to said supply means comprises a reservoir for containing respiratory gases and/or expired gases, so that said apparatus includes a rebreathing system and functions as a respirator or ventilator. 5. Breathing apparatus as claimed in any preceding claim, in which said automatic switching means includes a release mechanism for rendering said absorption means operative when said supply means is detached from said first respiratory gas source. 6. Breathing apparatus as claimed in any one of claims 1 to 4, in which said automatic switching means comprises a seal/obturator means which renderssaid absorption means operative when saidsupply means is detached from said first respiratory gas source. 7. Breathing apparatus as claimed in any preceding claim, including one or more of the following: a heat sink; an additional respiratory gas source; an additional CO^ absorber; an additional filter; an additional reservoir; an additional release means; and an additional valve or valves. 8. Breathing apparatus as claimed in claim 4, in which said reservoir is enlarged to make a combined mother and young child unit. 9. Breathing apparatus as claimed in any preceding claim, including a logic control circuit for controlling automatic delivery of apparatus, selection and supply of respiratory gases, broadcasting of instructions to passengers and providing an indication if apparatus has been tampered with or opened. 10. Breathing apparatus as claimed in any preceding claim, additionally including a guide means for guiding said release mechanism to ensure appropriate release of the reservoir or of operation of the filter.

Inventors: STEWART JOHN STEWART SIMPSON, STEWART, JOHN, STEWART, SIMPSON
Applicants: INTERTEK LTD, INTERTEK LIMITED
Application year: 1986
Main classification: A62B7
IPC codes: A62B7, A62B17