GB2196250A

GB2196250A - A fire extinguishing system

Info

Publication number: GB2196250A
Application number: GB08724503A
Authority: GB
Inventors: David Stevenson
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-10-21
Filing date: 1987-10-20
Publication date: 1988-04-27
Also published as: GB8625452D0; GB8724503D0

Abstract

A fire extinguishing system for an accommodation space such as an aircraft cabin comprises a plurality of face masks for the occupants of the space, each mask having a demand valve which opens to allow the escape of a breathable gas only when a suction is applied thereto, fire detectors (16) for detecting the presence of smoke or fire, and a gas delivery system (23) for introducing into the accommodation space a fire-extinguishing non-breathable gas from a source (22) thereof in response to actuation of the fire detector means (16) whilst at the same time connecting the said face masks to a breathable gas delivery system leading from a source (20) of breathable gas. <IMAGE>

Description

SPECIFICATION A fire extinguishing system Much attention has recently been given to the plight of victims of a fire in a confined space such as an aircraft from which escape is not always readily available due to the rapidity with which the fire can spread, the noxious gases which are produced thereby, and time which is taken for emergency escape apparatus to be brought into effect.

One of the most serious problems encountered in dealing with aircraft fires lies in the contradictory requirements of the passengers within the aircraft and the firefighters outside the aircraft. For the passengers, obviously, escape is imperative and early opening of as many escape hatches as possible is sought in order to evacuate the aircraft in an orderly manner as rapidly as possible. From the point of view of fighting the fire, however, opening the aircraft to allow the ingress of oxygen to support the combustion is detrimental. Airport fire services are on almost permanent alert and are almost always able to be in attendance at the scene of a fire in an aircraft within a matter of seconds rather than minutes. Sophisticated fire-fighting equipment is available to deal with any part of the fire on the outside of the aircraft.The majority of the combustible parts of an aircraft are housed within the outer shell, however, and consequently although any exterior fires can be contained quickly and easily from the outside by the fire-fighters present, access to the inside to deal with the fire, as with the escape of the passengers, necessarily involves making openings in the aircraft shell in order to gain access, thereby also allowing ingress to firesupporting oxygen.

It has been known for some considerable time that certain gases not only exclude oxygen but also have a very definite damping effect on the combustion reaction. One such gas, known under the trade name BCF, has been used for some time in fighting fires in aircraft engine bays and cargo bays, but it has not been possible to use it in passenger accommodation space because it is slightly toxic.

The present invention seeks to provide a system by which a fire-fighting gas such as BCF, (otherwise known as Halon 1211), Halon 1301, or the like, which is toxic, can be used in a passenger accommodation space in order to extinguish fires and save lives.

According to one aspect of the present invention, therefore, a fire-extinguishing system for an accommodation space comprises fire detector means operable to produce an output signal when the occurrence of a fire is detected, a source of non-breathable fire-extinguishing gas (such as BCF, Halon 1211 or the like), a first gas distribution system including at least one outlet to the said accommodation space, a control system operable to deliver the said fire-extinguishing gas to the said gas distribution system in response to the said output signal from the fire detector means, a source of breathable gas, a second gas distribution system including a plurality of delivery outlets each having a demand valve as herein defined, and means sensitive to the said output signal from the fire detector means operable to put the said breathable gas source into communication with the second gas distribution system.

As used in this specification the term "demand valve" will be understood to relate to a valve such as that used in underwater breathing equipment which is operated to allow the passage of gas in one direction only by a pressure differential which can be applied by a user attempting to inhale while sealing around the valve with the mouth or by means of a face-enclosing sealed mask. Clearly, if the said breathable gas is oxygen (which is one of the most convenient for the purpose) the beneficial effect of the fire-extinguishing gas would be lost if it were to be allowed to escape into the accommodation space. However, by providing the breathable gas distribution system with a demand valve at each outlet it is ensured that the breathable gas is only delivered into the accommodation space upon inhalation by a user. Any unused delivery outlets will thus remain closed.

Further, the terms Halon 1211 and Halon 1301 will be understood to refer to bromochlorodifluoromethane and bromochlorotrifluoromethane respectively.

The fire-extinguishing system of the present invention involves the provision of a plurality of breathable gas delivery outlets preferably in the form of face masks, one for each passenger or other occupant of the space. In an aircraft every occupant has an individual seat and consequently the possibility of an inadequate supply of outlets is avoided. Furthermore, the gases envisaged for fire-extinguishing purposes such as BCF or Halon 1211, are only slightly toxic and the risk of permanent injury from inhalation is very much less, should it happen that the gas is allowed into the accommodation space before every passenger is able to make use of the face mask provided for him, than is the risk of injury from the inhalation of the toxic gases produced as the result of combustion within an aircraft.

Of course, the breathable gas source may, in fact, be permanently in communication with the second distribution system, with a suitable alarm circuit or other release mechanism making the face masks available upon detection of a fire.

Any appropriate fire detection means, such as smoke detectors, temperature sensors or the like may be employed, and the system may include a delay circuit for ensuring that the breathable gas distribution system is put into operation in advance of the delivery of fire-extinguishing gas to the delivery outlets of the first distribution system.

One embodiment of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the interior of an aircraft showing the provision of a face mask for the breathable gas distribution system; and Figure 2 is a schematic circuit diagram illustrating the component parts of a fire-extinguishing system formed according to the principles of the present invention.

Referring now to Figure 1 a conventional aircraft seat is illustrated and generally indicated with the reference numeral 11. Above the seat 11, in a hatch above the passenger's head is a container 12 housing a face mask 13 joined by a flexible duct 14 to a fixed distribution system (not shown). The casing 12 includes a closure flap 15 which is normally held in the closed position so that the fact mask is housed inside the container 12 and is not accessible. Upon operation of the fire-extinguishing system, however, automatic release mechanisms (not illustrated) are triggered to open the flaps 15 allowing the face mask 13 to fall to a position where it becomes accessible to the passenger in the seat behind the seat 11. It is only necessary, in an emergency, therefore, to grasp the mask 13 and place it over the face for a supply of breathable gas to become available.It is envisaged that an aircraft fitted with the fire-extinguishing system of the present invention would have such a structure in the vicinity of the luggage rack above every seat and in a similarly convenient location for the crew seats, together with a number of additional outlets, not specifically related to the seating pattern, for the use of crew members or passengers who may not actually be sitting in their seats upon the occurrence of an emergency.

Referring now to Figure 2 there is shown an outline schematic diagram of a fire-extinguishing system formed according to the present invention. The system illustrated comprises a plurality of fire detectors generally indicated 16 linked together in a circuit to a control unit 17 which is constantly energised to monitor the state of the detectors 16. The fire detectors 16 may be of any known type, including temperature sensors, smoke detectors and the like, and need not necessarily be all of the same type, but may be different from their neighbours, either connected in a single circuit as illustrated or in a number of parallel circuits each operable when energised, to trigger the alarm unit 17.The output from the alarm unit 17 passes to a public address system 18 including a recorded message instructing the passengers in the use of the face masks 13 which become immediately accessible, as described in relation to Figure 1, upon triggering of the alarm circuit 17 and commencement of the public address through the system 18.

A line 19 leads from the control unit 17 to a breathable gas source 20, which may be oxygen, nitrogen, a mixture thereof or any other breathable mixture capable of supporting life for a short period of time. In this connection it is envisaged that an automatic fire control system such as that of the present invention should be able to contain any outbreak of fire within a matter of minutes given that the location of the fire must be contained within the aircraft which, unless the doors are actually open for the entry or exit of passengers, would be in a closed airtight state. The ingress of the fire-extinguishing gas into such a closed space immediately upon the detection of a fire should, therefore, act to extinguish the fire almost immediately, preventing it from developing into a major conflagration.The line 19 also leads via a delay circuit 21 to a second source 22 of gas, this gas being the fireextinguishing gas which may be BCF (Halon 1211), Halon 1301, or other known or yet-tobe-discovered fire-extinguishing gas. The purpose of the delay circuit 21 is to ensure that the breathable gas delivered from the source 20 is available at the face masks 13 several seconds before the toxic non-breathable fireextinguishing gas is delivered from the source 22. As can be seen in Figure 2 the source 22 delivers gas to a distribution network 23 including gas outlets 24 spaced around the interior of the aircraft so that within only a few seconds of the delivery system 23 being connected to the gas source 22 the whole of the interior space of the aircraft can be filled with the fire-extinguishing gas under super-atmospheric pressure.

Once the fire has been brought under control the fire-extinguishing gas may be vented from the interior of the aircraft and the passengers evacuated using the known emergency evacuation equipment and procedures already in existence. Even if the evacuation procedures are commenced prior to the removal of the fire-extinguishing gas the risk from inhalation of such gas for only a short period is relatively small, and certainly very much less than the risk of injury from inhalation of toxic combustion products.

As illustrated in Figure 2, the delivery system 23 also has a flow control valve and flowmeter 25 to allow for different cubic capacities of loading of aircraft (by varying the delivery flow rate of the fire-extinguishing gas) that is by reducing the flow rate when the aircraft is more fully loaded and therefore when the difference between the total interior volume of the aircraft and the volume occupied by passengers and/or cargo is at a mini mum, and conversely by increasing the flow rate when the aircraft is less fully loaded and therefore when the above defined difference volume is at a maximum. This will enable the correct percentage of fire extinguishing gas to be distributed throughout the aircraft in order to minimise toxicity and cost.

Claims

1. A fire extinguishing system for an accommodation space, comprising fire detector means operable to produce an output signal when the occurrence of a fire is detected, a source of non-breathable fire-extinguishing gas (such as Halon 1211, Halon 1301, or the like) a first gas distribution system including at least one outlet to the said accommodation space, a control system operable to deliver the said fire extinguishing gas to the said gas distribution system in response to the said output signal from the fire detector means, a source of breathable gas, a second gas distribution system including a plurality of delivery outlets each having a demand valve as herein defined, and means sensitive to the said output signal from the fire detector means operable to put the said breathable gas source into communication with the second gas distribution system.

2. A fire extinguishing system as claimed in Claim 1, in which the breathable gas source is permanently in communication with the second distribution system.

3. A fire extinguishing system as claimed in Claim 1 or Claim 2, in which the breathable gas delivery outlets are formed as face masks adapted to seal around the mouth and/or nose of a user.

4. A system as claimed in Claim 3, adapted for use in an aircraft having a plurality of face masks stored in respective storage compartments associated one with each seat on the aircraft, and releasable so as to be made available to the passengers.

5. A fire extinguishing system as claimed in Claim 4, in which the release of the face masks to make them available to passengers is effected automatically in response to the said output signal from the fire detector means.

6. A system as claimed in any preceding Claim in which the breathable gas in the said second gas distribution system is oxygen.

7. A fire extinguishing system as claimed in any of Claims 1 to 5, in which the breathable gas in the said second gas distribution system is nitrogen.

8. A fire extinguishing system as claimed in any preceding Claim, in which the non-breathable fire extinguishing gas in the said first gas distribution system is Halon 1211 or Halon 1301.

9. A fire extinguishing system as claimed in any preceding Claim, further including a delay circuit associated with the said first gas distribution system operable to ensure that the said breathable gas is available through the said second gas distribution system in advance of the delivery of fire extinguishing gas to the delivery outlets of the said first gas distribution system.

10. A fire extinguishing system substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.