GB2214685A - Fire escape system - Google Patents

Abstract

Indication of a fire escape route from a system such as an underground railway which has one or more enclosed locations and one or more routes to one or more exits from the system is provided by one or more beams 20 of laser light along a route from at least one of the locations to at least one of the exits when a smoke condition exists in the system, the laser beam or beams providing an indication of the escape route. The beam may be shrouded so as not to be visible but part of the beam is diverted to illuminate direction signs or instructions or mixtures thereof disposed along the route or routes. As shown, beam splitting mirrors 30, 40, 50, 60 direct part of the beam down to signs 41, 61 which may be holographic or such as to luminesce or fluoresce. Fibre optic cable may also be employed. <IMAGE>

Description

"FIRE ESCAPE SYSTEM" The present invention relates to systems for assisting escape from enclosed areas in which there is an uncontrolled fire. Apart from the risk of death due to burning a frequent cause of death in fires is inhalation of smoke. Whilst smoke inhalation can cause death rapidly depending on the nature of the materials which are burning the risk of death is increased the longer a person is exposed to smoke. Recent fires in underground railway systems have demonstrated the need to make it possible to find ones way through smokefilled passages to an exit.

The present invention is concerned with providing visible indication of an escape route through an enclosed smoke obscured area. It has been developed with the problems which arise in fires in underground railway systems in mind and will be described with particular reference to such systems. It is however applicable to indicating an escape route from any enclosed location e.g. a room to the outside atmosphere where a multiplicity of routes are available or large rooms have to be traversed, having a remote exit or exits which have to be found to continue the route and which will be liable to be obscured by smoke.

Examples of such other locations include hotels, conference centres, buildings with atria, shopping centres or malls, multistory public buildings, mines, sports centres, oil rigs and oil rig accomodation, ships, and blocks of flats and domestic housing is not excluded.

Ordinary incandescent or neon lights and signs which have individual discrete locations rapidly become obscured in smoke quite apart from being more liable to fail when the temperature rises.

In the Kings Cross fire of 1987 the lighting system proved inadequate to enable people to find their way around in the smoke. Fire officers followed the walls by touch, there being no indication of any route to platforms where passengers needing to escape might be located.

The present invention is based on the realization that a highly collimated beam of light which tends to have low visibility in clean dust-free air becomes visible in smoke because the smoke particles diffuse the light in the beam. The most readily available current form of such a beam is a beam of laser light, which, as is well known, is a monochromatic (i.e.

single wavelength) coherent (i.e. all waves in phase) beam of radiation. Laser beams may be generated by exciting the electrons in material enclosed in a space bounded by opposing mirrors one of which has an exit aperture so that photons emited by electrons decaying from an excited state can emerge from the aperture and do so as the said coherent monochromatic beam. This may be a continuous wave or pulsed mode laser beam.

The laser may be a gas laser e.g. helium-neon, argonkryptron, or helium-cadmium, a solid state laser or a dye laser or other effective laser.

When the term laser beam or laser light is used herein it is to be taken to include any light beam having the highly collimated properties of a laser beam however the beam is generated, however beams actually generated by a laser are much preferred.

The power rating of the laser should desirably be chosen to be such as to penetrate the anticipated maximum smoke particle density whilst being of low enough power and so located to be such as not to cause eye damage; however even if the beam is such as eventually to be obscured by the smoke at the very height of the smoke intensity of a fire, it will still perform a very useful function by remaining visible much longer than other light sources. If the laser is located at a position where only deliberate efforts would enable a person to achieve direct intra-beam viewing i.e. to place their eye in the laser beam and look at the laser source then higher power ratings could be used.

If the laser beam is to be positioned where direct intra-beam viewing would bepossible accidentally or wilfully i.e. at head height or lower or where it is at a height contrary to local Health and Safety Regulations then the beam should be shrouded e.g. directed along a duct whilst access to the beam by the smoke is maintained, the shrouding being such as to prevent intra-beam viewing whilst maximizing the amount of the beam which can be seen. Such a duct could be a channel e.g. U-shaped and whilst open, to enable the beam to be seen, narrow enough to prevent direct intra-beam viewing, or could be an apertured tube.

In the U.K., Health and Safety Regulations stipulate that class 2 lasers, which are low powered lasers emitting visible radiation (400-700 nanometres) are not inherently safe but eye protection is normally afforded by aversion responses including the blink reflex. British Standard Specification No. 4803 identifies class 2 lasers as having an average power of 1 milliwatt.

Class 3A lasers have an output power of up to 5 milliwatts (as collected by an 80 mm diameter measuring optic) for continuous wave lasers and 5 milliwatt peak power for repetitive pulsed and scanning lasers that operate in visible wavelengths. The irradiance (beam power density) at any point in the beam does not exceed 2.5 milliwatts per sq.cm. i.e. equivalent to 1 milliwatt over a 7 mm diameter pupil size. Protection for the unaided eye is again afforded by aversion responses, including the blink reflex.

Class 3B lasers emit visible radiation at either an output power not exceeding 0.5 watts in the case of continuous wave lasers or in the case of pulsed lasers a radiant exposure of less than 105 Jim'2, Direct intra-beam viewing of these class 3B lasers and specular reflections are hazardous.

Class 4 lasers are devices with output powers exceeding those of class 3B lasers. In addition to the hazard from intra-beam or specular reflections they are capable of producing hazardous diffuse reflections.

They may also present a fire hazard.

The risk of such specular or diffuse reflections from the mirrors involved in the system of the present invention can be minimized or avoided because the mirrors are intended to be fixed (and the shrouding aspects afford secure fixings which could be made difficult to tamper with) and any which move can be protected by an interlock on the component itself e.g.

if a mirror is moved outside preset limits the laser is switched off, thus providing a fail-safe device.

Class 4 lasers if used should be positioned and shrouded in such a way that the risk of diffuse and specular reflections is contained to acceptable levels e.g. by having the laser beam viewed through controlled openings, which could be either shrouded or masked or be protected by tinting, bearing in mind the risk this use of the laser is avoiding and such as to minimize the risk of the laser beam itself being a cause of fire.

All laser beams used will be provided with beam stops or absorbers which are non-flammable and absorb the wavelength of the laser beam in question.

Emissions outside the 400-700 nanometre range are preferably kept to a minimum.

Class 2 and class 3A lasers may be used above eye level preferably at high elevations e.g. at least 3 metres above the highest surface on which a person can stand below them, or at lower levels but then desirably are shrouded to prevent direct intra-beam viewing.

Class 3B lasers should be mounted and shrouded to prevent intra-beam viewing and also to ensure that the minimum distance to which the eye can be brought to observe the beam is at least 5 cms and preferably at least 10 cms. Combinations of different power lasers could be used with smoke density sensors switching into operation the higher power lasers only when smoke density levels reach such values as to attenuate the beam sufficiently to reduce the specular and diffuse reflections to non-hazardous levels.

As distinct from discrete light sources a laser beam affords a continuous strip of light which when revealed by smoke can be followed continuously by the escaper. A laser beam can be bent e.g. refracted e.g.

by a prism or reflected by a mirror and can thus pass through a curved tunnel or pass round a corner substantially without break.

A laser beam can also be split e.g. by a part transmitting/part reflecting mirror. Mirrors with the split between reflection and transmission falling in a wide range of individual values can readily be obtained e.g. a 50/50 split, an 80% reflection/20% transmission or higher reflection level, or to an 80% transmission/20% reflection or higher transmission level as well as intermediate values can all be obtained.

Mirrors of this type are obtainable typically from Messrs. Specal Ltd. Laser beams having power ratings 3 milliwatts and 6 milliwatts produced by Gas helium-neon lasers of white colour have been satisfactorily split, 50% transmission/50% reflection, and 80% transmission/20% reflection using special mirrors.

These lasers were Scientif ia-Cook Ltd lasers models EL H/3 (3 mWatt (milliwatt)) and EL-H/6 (6 mWatt (milliwatt)).

Another possibility is that the shrouding of the beam may be complete over parts of the route to escape by being conveyed through a wave guide e.g. a fibre optic cable, though such a waveguide should permit light to radiate from it so that its position is apparant and it can also be followed.

This could be useful where particularly sharp corners or complex changes in direction are needed and the use of mirrors or prisms and duct type shrouding would intrude objectionably into the passage way.

Desirably these waveguide aspects would be used downstream from the primary location being evacuated e.g. an underground station platform since the interaction of the smoke with the beam is a forceful visual warning of the hazard condition. This change in appearance would not occur when the beam is totally enclosed in a waveguide or optical fibre.

A disadvantage of waveguides is that their surface can be obscured by a film of dirt or smoke and they are liable to damage if not encased.

According to the present invention a method of providing an indication of an escape route from a system having one or more enclosed locations and one or more escape routes to one or more exits from the system comprises providing one or more beams of laser light along the said escape route so that when a smoke condition exists in the said system, the laser light beam provides an indication of the escape route. This indication of the route may be effected by the laser beam itself being rendered of enhanced visibility by the smoke at least at the said location, escape from the system thereby being facilitated.

At least one of the beams of laser light is preferably substantially continuous.

Reference to a substantially continuous beam means a beam which extends substantially from the remote location to an exit; it may be made up of a number of sequential lasers but the beginning of the second beam is next to the end of the first beam and so on so that a person following the first beam will immediately be able to locate the second beam and so on to the exit; a continuous beam may have bends or corners in it and may have its intensity reduced along its length by diversion of part of the beam and part of the beam may be located within an optical fibre.

Alternatively the laser beam may be used to illuminate direction signs which themselves indicate the escape route. Splitter mirrors may be used to divert just sufficient of the beam to achieve the necessary illumination.

Such a system permits the beam to be shrouded from the eye and only be open to the wall and thus may permit higher power lasers to be used. Combinations of lower power visible beams and higher power shrouded beams illuminating the wall may be used, and may be operated together or in sequence either the higher or the lower power devices being used when there is less smoke.

Direction signs and instruction panels which are to be so illuminated are preferably made of highly reflective material or material which luminesces or fluoresces in the particular laser light being used.

Clearly a combination of a visible beam and diversion of some of the beam to illuminate signs can also be used.

The signs may be such that they are normally invisible and an advantage of this is that it reduces the risk of them being defaced and also concentrates attention on them when there is a hazard situation.

Preferably the laser beam is provided or established by being switched on in response to detection of fire or smoke anywhere in the system. The switching on of the laser beam may be carried out by automatic means responsive to the detection of fire or smoke in the system or may be switched on by a human or computer controller after an assessment of the severity of the condition detected and its location in the system. The system may be provided with a mimic diagram on which are represented the location of the smoke or fire detectors and the structure of the system e.g. the rooms, passages, corridors, tunnels, hallways, platforms, lifts, escalators etc. and the laser beams.

The mimic diagram can be interrogated by a human operator or computer to determine the source and severity of the detected condition and the safest routes to one or more exists from each part of the system and the appropriate laser beams can then be actuated.

Such actuation could be under automatic control of computing means running under software control.

As mentioned above the laser beams or other laser beams may also be used to illuminate normally invisible direction signs or escape instructions or both.

If a single laser beam is to be used part of the beam may be diverted e.g. by mirror splitters to illuminate direction signs or instructions. Such signs are preferably holographic or other images which are invisible in incandescent or fluorescent light but visible in laser light and may be such as to luminesce or fluoresce.

An advantage of only establishing the laser beam in response to detection of a smoke or fire condition is that the presence of the beam revealed by the smoke (or dust in the air in an underground railway system) acts as an automatic visual alarm signal. Since it then affords a method for escape it may be anticipated to have a calming effect on the persons using it to escape from the system. The directions and instructions may be positioned adjacent the beam or on a more remote location where more people could see it simultaneously (as might be advantageous in the early stages of an emergency before the smoke had become too thick). Posters visible in ordinary light advising users of the system about the laser escape route indicator and thus making them aware of it would be also advisable.

Pulsed wave lasers could be used to provide directional instructions intrinsically in the beam, the escaper following the direction of the pulse; clearly the pulse speed would have to be slow enough for the direction of the pulse to be visible.

Directional instructions to different escape routes could also be given by arranging beam diversion means so that different indications of the direction to be followed could be illuminated at will. Such beam diversion means could be splitter mirrors movable between positions where in one position one direction indicator is illuminated and in another position a different indication of direction is illuminated. The mirrors could be motorized or solenoid driven under appropriate control e.g. from a central controller.

A directional "arrow" could also be achieved by setting "beam splitters'1 in the path of the main beam, first to split the beam in two into opposite directions, which would then be reflected by angled mirrors sending the beam back to its original position where it would then be straightened by two further mirrors or a converging lens so as to reconstitute the laser beam which would then continue undiminished.

The invention also extends to a system for imparting directional information to a laser beam which comprises placing beam splitter means in the beam so as to direct a proportion of the beam or the whole of the beam away from the axic thereof, collector means adapted to collect the said diverted laser light and return it back to the axis of the said beam at a location spaced along the beam from the beam splitter and converging means for converging the said returned laser light and directing it along the axis of the laser beam.

The beam splitter could be a first mirror transmitting a proportion of the beam (e.g. 50%) and reflecting the remainder to one side of the axis of the original beam where a fully reflecting mirror reflects the beam back to a converging lens positioned at the axis of the beam, and a second mirror reflecting the remainder of the beam to the other side of the axis of the original beam where another fully reflecting mirror reflects the beam back to the converging lens, the converging lens being such as to converge the reflected laser light into a beam parallel to the original laser beam.

The direction to be followed could also be indicated by having lasers set up in opposing positions, so that the end point or beam stopper can be percieved as the direction to be followed; one or other beams would be switched on thus indicating the direction to be followed. This would be particularly useful with a pulsed laser.

Pairs of lasers could also be used, one with a continuous beam and the other with a pulsed beam.

We now turn to specific consideration of the use of the system in an underground railway system.

Each platform would have a laser beam, preferably ducted, depending from the roof of the platform about midway across its width and extending substantially its full length. The beam would be split and part diverted down each exit e.g. by use of beam splitting and fully reflecting mirrors. If there were a number of exits, more than one laser could be used so as to provide a more intense beam for diversion down the exit tunnel.

Ideally one laser beam would be provided for each tunnel so that each beam could be diverted unattenuated down the tunnel to which it was assigned. Portions of the beams e.g. minor portions e.g. 10 to 30% such as 20% could be diverted to illuminate normally invisible direction signs and instruction panels. Splitter mirrors as described above could be used for this purpose. Direction signs would best be located on the wall of the platform. However as discussed above at least some of the instruction panels might best be located remote from the beam e.g. on the far wall or roof of the tunnel beyond or over the tracks.

A feature of the smoke pattern in fires in underground railway systems appears to be that the smoke is more dense at the floor than at the ceiling. Thus having the directional beam and direction indicators and instructions at a high rather than a low level in the tunnel may be advantageous. This is the reverse of what appears to happen in domestic fires. The pattern of smoke build up characteristic of the particular system should therefore be born in mind when installing a system in accordance with the present invention.

Another advantage of having the beam at a high level is that higher power lasers or less ducting may be used.

However in the exit tunnels, which in general have lower ceilings, shrouding or ducting may well be prudent even with lower power lasers, or waveguides could be used at least for part of the escape route.

When the system is being installed during the building of an environment or system it may be convenient to sink the ducts into channels in the walls at about head height or lower. When the system is to be installed in an already existing environment the ducts can be wall or surface mounted.

The use of ducts has the advantage of providing a ready location and mounting for beam deflectors to bend the beam and for beam reflectors and beam splitters.

The ducting is best apertured to ensure adequate access of the smoke to render the beam visible but it may also be desirable for one or both upstanding walls of a duct to be transparent or translucent. When higher power lasers such as class 4 or even class 3 are being used transparent duct walls disposed between the beam and the escapers head height may well fulfill a useful safety role for the eyes.

In certain systems an escape route may have branches connecting it to a number of platforms.

Clearly it is desirable for the beam to indicate which is a feeder tunnel and which is the escape route. This could be achieved by using different coloured lasers for the different ranking of tunnels e.g. red for a feeder and green for a main route or having the main route a double or triple beam possibly obtained by splitting the beam or providing a separate extra laser beam running parallel to the original beam.

The invention thus extends not only to a method as set out above but also to a system such as an underground railway station provided with means for carrying out the method.

The invention also extends to apparatus for indicating an excape route from a location via one or more passages to one or more exits, the apparatus comprising laser means mounted in the said location so as to provide one or more, preferably substantially continuous, laser beams from a location to an exit via one or more passageways, beam stopping means for the end of each laser beam and means for directing a laser beam from within the location to an exit therefrom and thence to a passageway or passageways connecting the exit from the location to the exit from the system, and means for directing the or a further laser beam or beams along the said passageway or passageways to an exit from the system.

It will be appreciated that the beam could be directed either outwardly from the location to the exit or inwardly from the exit to the location and different directions of the beam could be used for different parts of the route; all that is necessary is that a substantially continuous beam be established extending between the location and the exit.

Whilst the invention has been described with reference to evacuation from a location it will be appreciated that any one located in one of the passageways will be able to pick up the escape route.

Detection of the correct direction to follow along the beam is also provided for as described above.

All parts of the system are desirably provided with route indicating means in accordance with the present invention and may be led to a single escape route via feeder beams as described above or could be led to a different escape route. When more than one escape route is provided in a system these are preferably differentiated so that if one escape route becomes blocked or dangerous escapers can be directed to the or one of the other routes.

In addition to the system and apparatus aspects of the present invention it also extends to novel shrouding means preferably provided with means for mounting the various elements of the system and to an assembly of the shrouding with the elements mounted thereon and to a kit of parts of the shrouding and individual elements.

Apart from the safety aspects of the shrouding it also provides a very convenient and rapid way of aligning the components of the system and a very adaptable way of mounting the whole assembly in the system e.g. in an underground railway station.

When elements of the system such as beam diverters are to be movable under remote control the shrouding can also provide a mounting for the drive means e.g. a motor or solenoid and furthermore for the power supply and control wires therefor. Indeed the shrouding also provides a ready route and mounting means for the power and control cables for the lasers involved in the system and for smoke, fire or temperature detectors associated with the system even if they are not actually mounted on the shrouding. The shrouding could also carry cabling for loudspeakers whereby audio instructions could be given as well as for microphones or telephones which could assist in the detection of survivors or the reporting of an alarm condition to a central control location (which could itself be remote from the system actually being protected).The shrouding could also carry such loudspeakers or microphones. It could carry telephones at locations where the shrouding was at head height or there abouts or lower.

The invention may be put into practice in various ways and one specific embodiment as applied to an underground railway station will be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic cross-section of a platform in an underground railway system; Figure 2 is a diagrammatic longitudinal section on the line II-II of Figure 1 of part of the platform shown in Figure 1 showing an end exit tunnel and a side exit tunnel; and Figure 3 is a diagrammatic perspective view of an underground railway station showing one of several platforms, and various exit tunnels.

Figure 1 shows one end of a platform P1, with a train tunnel TT and a platform exit PE1 leading to a tunnel T1. Mounted on the end wall of the platform is a laser L1 positioned to direct its beam 20 (see Figure 2) along the platform generally parallel to the wall.

The platform here is shown as being straight; when the platform is curved, the beam will be made up of a number of arcs created by bending the beam an appropriate extent by suitable beam bending means (e.g.

a prism or mirror) in a series of straight interconnecting lines following the curve.

High and low level smoke detectors 21 and 22 are secured to the wall of the platform. These are set to detect a predetermined smoke density and to send a signal to a central controller (not shown). Alternatively they may directly activate the laser L1.

The laser L1 may be provided with power from a central location or have a local standby e.g. battery driven power supply and may be under central or local control as by the smoke detectors.

The laser beam 20 is split just after emerging from the laser L1 by a beam splitting mirror 30 which allows a major part of the beam to be transmitted while reflecting the remainder downwards to a 100% reflecting mirror 31 which reflects the beam along the roof of the exit tunnel PE1. The diminished beam 23 now continues to a motorized beam splitting mirror 40 which allows a high percentage e.g. 90% to pass and directs the remainder e.g. 10% down onto the wall onto one or other of two direction signs e.g. arrows 41 and 42. These are invisible in incandescent or fluorescent light but become strongly visible in laser light. They may be holographic or be such as to luminesce or fluoresce.

With the mirror in one position the arrow 41 will be illuminated directing escapers to the tunnel PE1, with the mirror in the other direction escapers will be directed in the other direction.

The further diminished beam 24 now continues to a stationary beam splitting mirror 50 which allows a high percentage e.g. 90% to pass and directs the remainder e.g. 10% across the tunnel to the far wall beyond the tracks onto a panel 43 giving instructions about the escape route and the direction indicating system. This panel or the letters are again invisible in incandescent or fluorescent light, or, if visible so as to instruct users prior to an alarm condition, are rendered of increased visibility in laser light. They may be holographic or be such as to luminesce or fluoresce.

The diminished beam 25 now continues to a beam splitting mirror 60 which allows part of the beam to be transmitted while reflecting the remainder downwards to a 100% reflecting mirror 61 which reflects the beam along the roof of the side exit tunnel PE2. The further diminished beam 26 now continues along the platform and is used to illuminate direction signs and instructions as well as such other exit tunnels as may emerge from the platform. (Figure 3 shows four such tunnels but for simplicity we will discuss the arrangement of Figure 2 as if only the two exit tunnels shown are provided.) Assuming that it is desirable that the intensity of the beam used to indicate the entrance to a tunnel is the same for each tunnel it will be necessary to divert a higher % of the beam at the mirror 60 than was necessary at the mirror 30.The appropriate % transmission and % reflection at each mirror will depend on the dimensions of the platform and the number of exits and the number of directions and instructions it is wished to illuminate.

The laser L1 on the platform being positioned high up can be of high power; lower power lasers can be used in the tunnels to carry the substantially continuous laser light beam on through the tunnels to the exit and illuminate direction indications from time to time.

Such additional beams may be in parallel with the original beam or that beam may be stopped with a beam stop and the additional beam carry on in replacement of the original beam.

Returning to Figure 2 the beam 26 can be used to illuminate further direction indicators but since we have made the assumption that PE1 and PE2 are the only exits from the platform P1 such further arrows would be in the sense of arrow 41 directing escapers on the platform back to the exit PE2 or PE1.

Turning now to Figure 3 the platform P1 is provided with exits PEl and PE4 at the ends of the platform and PE2 and PE3 as side exits. PE4 links directly to an exit 3 via a tunnel T4 and is the only platform in the station provided with such a direct emergency exit.

PE1 links directly via a tunnel T1 to a main concourse tunnel T7 from which the normal entrance and exit is via an exit TE7, a tunnel T8 and a tunnel exit TE8 to an escalator hall EH from which access to the main exit 1 is via an escalator El.

The concourse tunnel T7 is provided with an exit TE9 to a tunnel T9 which leads directly to an emergency exit 2.

The concourse tunnel T7 also has exits TE5 and TE6 which lead via tunnels T5 and T6 to other parts of the station e.g. other platforms.

The concourse tunnel T7 is also fed by exit TE2 to a tunnel T2 and TE3 to a tunnel T3. However tunnels T2 and T3 each branch. T2 branches into one branch T2A leading to platform P1 by the exit PE2 and the other branch T2B leads to another part of the station e.g. a platform parallel to P1. T3 branches similarly into T3A and T3B; T3A connects via exit PE3 to P1 and T3B connects to the same platform as T2B.

Each of the tunnels T1 to T9, each of the platforms and EH and El are provided with the means to establish a substantially continuous laser beam therein and these beams link up to form a substantially continuous network leading to the exits. Preferably the laser beams in tunnels T8, T9 and T4 can be separately switched on and off independently of each other and the remainder of the system whilst the beams on each platform and its exit tunnels are separately controllable. As a fail safe whilst the beams on the platforms have the function of indicating the location of the exits and the beams in the tunnels T1, T2, T3, T5 and T6 are also separately controllable, it may be desirable for the platform beams to be taken at least as far as T7 even if added to by additional beams in these tunnels.

These various beams may be under a central controller so that particular beams can be switched off to prevent escapers being lead to the seat of the fire.

However the escapers may themselves be able to sense approach to the seat of the fire and it may be better to maintain the route indications on at all times. This is a matter for experimentation on the use of the invention in a particular environment.

Possible use of the system will now be described in various scenarios.

Scenario 1: Assume a fire in El. The beam in T8 could be switched off or motorized beam splitters used to indicate arrows pointing towards T7. TE7 could be provided with a motorized beam splitter to illuminate a "danger no entry sign" (as could all exits TE1-TE9 and PE1-PE4). Escape could then be via TE9 to EXIT 2.

Scenario 2: The fire in El has burnt down T8 and is emerging from TE7. Escapers in T2, T5 and T6 could go back to P1 and escape via PE4 and T4 or less advisedly via PE3, T3A, T3, TE3, TE9 and T9 to Exit 2.

Scenario 3: Assume a fire between TE7 and TE9.

Escapers from T1, T2, T5 and T6 could escape via TE7 and T8 and EH to exit 1. Escapers from T3B or T2B or T3 could escape via P1 and T4 or less advisedly via T2 or T1 and TE7 etc.

In scenarios 2 and 3 appropriate no entry signs at the relevant tunnel exit or platform exits would be illuminated and the direction arrows in the tunnels would be reversed to direct escapers away from the seat of the fire.

We have mentioned the desirability of differentiating a main escape route from feeder tunnels. In Figure 3 T2, T3 and T7 are main escape tunnels whilst T2A, T2B, T3A, T3B, T5 and T6 are feeder tunnels. T1 and T4 and T9 are also main escape tunnels. The main escape tunnels should preferably have double beams whilst the feeder tunnels have single beams.

It will be understood that these scenarios are merely illustrative and the logic to be used in any given environment will need individual development.

Claims (21)

1. A method of providing an indication of an escape route from a system having one or more enclosed locations and one or more routes to one or more exits from the system which method comprises providing one or more beams of laser light along a route from at least one of the locations to at least one of the exits when a smoke condition exists in the said system, the laser beam or beams providing an indication of the escape route.

2. A method as claimed in Claim 1 in which at least one of the beams is substantially continuous.

3. A method as claimed in Claim 1 or Claim 2 in which the beam itself indicates the escape route by being visible to persons in the system and being made visible by scattering of light in the beam by the smoke.

4. A method as claimed in Claim 1 or Claim 2 in which the beam is shrouded so as not to be visible but part of the beam is diverted to illuminate direction signs or instructions or mixtures thereof disposed along the route or routes.

5. A method as claimed in Claim 1, 2, 3 or 4 in which part of the beam is diverted to illuminate one or more direction signs or instructions or mixtures thereof.

6. A method as claimed in any one of Claims 1 to 5 in which the route to an exit is differentiated from locations or feeder passages connecting locations to the route by the colour or number of beams used in the route as compared to those used in the locations or feeders.

7. Apparatus for indicating an escape route from a location via one or more passages to one or more exits which comprises, means for providing a laser beam mounted in the said location so as to provide one or more substantially continuous laser beams from a location to an exit via one or more passageways, beam stopping means for the end of each laser beam and means for directing a laser beam from within the location to an exit therefrom and thence to a passageway or passageways connecting the exit from the location to the exit from the system, and means for directing the or a further laser beam or beams along the said passageway or passageways to an exit from the system.

8. Apparatus as claimed in Claim 7 including one or more means for directing laser light onto one or more direction indicators or sets of instructions for excape.

9. Apparatus as claimed in Claim 8 in which the direction indicators or sets of instructions for escape are invisible in incandescent or fluorescent light.

10. Apparatus as claimed in Claim 8 or Claim 9 in which the means for directing laser light onto the indicators or instructions comprises means for diverting a proportion of the said substantially continuous laser beam onto the said indicators or instructions whilst permitting the rest of the beam to continue.

11. Apparatus as claimed in any one of Claims 7 to 10 including smoke or fire or temperature detector means and means responsive to detection of an alarm condition in the system for establishing the said substantially continuous laser beam.

12. Apparatus as claimed in any one of Claims 7 to 11 including means for shrouding the said substantially continuous laser beam or parts thereof.

13. Apparatus as claimed in Claim 12 in which the shrouding means is such as to permit the beam to be visible to persons in the system but such as to prevent direct intra-beam viewing or placement of the eye closer than the locally stipulated safe viewing distance for the type and power of laser being used and the power of the beam at the location in question, whilst leaving access for smoke to the beam.

14. Apparatus as claimed in Claim 12 in which the shrouding means is such as to prevent the beam being visible to persons in the system and means are provided for using the beam or a proportion thereof to illuminate direction indicator means which are continuous or are at spacings such that a continuous pathway through smoke can be perceived by a person following the succession of indicators.

15. Apparatus as claimed in any one of Claims 12 to 14 in which the shrouding means carries mounting means for the beam diverting means or the beam bending or reflecting or absorbing means or for the laser means or for the smoke, fire or temperature detection means, or means for mounting the shrouding in the system or for connecting such mounting means to the shrouding or any combination thereof.

16. Apparatus as claimed in Claim 15 in which the shrouding means has mounted on it the laser or lasers and beam stops for each beam, beam diverting means, and beam bending means, e.g. which may diffract or reflect the beam.

17. Apparatus as claimed in any one of Claims 13 or 14 to 16 when dependent on Claim 13 in which the shrouding means has an aperture or apertures disposed along its length to permit access of smoke to the beam and the depth of the shroud from the aperture or apertures and the location of the beam within the shroud and the width of the apertures are such as to prevent direct intra-beam viewing.

18. Apparatus as claimed in Claim 17 in which the surface of the shroud facing persons in the system or part of the said surface is afforded by transparent material.

19. Apparatus as claimed in Claim 18 in which the transparent material is free of apertures.

20. Shroud means as claimed in any one of Claims 15 to 19.

21. A kit of parts consisting of shroud means as claimed in Claim 20 and one or more of laser means, laser stop means, beam diverting means, beam bending means, and direction signs or instruction sets which are rendered visible by laser light.