GB2472466A - System for assisting the rescue of vulnerable persons - Google Patents

Abstract

A system is provided for assisting the rescue of vulnerable persons, such as young children, the elderly, and the disabled, from buildings, particularly by a fire rescue crew. Conventionally, a fire rescue crew, upon entering a burning building 1, will search rooms 1A to 1H in a strictly specified order to ensure that every room is searched. This procedure however does not ensure that top priority is given to rooms that are likely to contain vulnerable persons. This problem is addressed by the disclosed system which utilises a visual signalling unit 5 mounted on or adjacent the door of a room 1F identified as containing a vulnerable person and visible to rescuers in the access area A. The signalling unit 5 comprises a microphone (6,fig.2); means (7-11,fig.2) for processing an output of the microphone to identify a sound emanated from a smoke alarm; and means (12,12A,fig.2) for generating, in response to such detection, a visual signal, visible to rescuers in the access area A. Activation of the visual signal may be delayed by a predetermined period to allow for longer observation of a sound potentially emitted from a smoke alarm in order to avoid false activations, and to account for the response time of the fire rescue crew.

Description

A System For Assisting the Rescue of Vulnerable Persons This invention relates to a system for assisting the rescue of vulnerable persons such as young children, elderly and the disabled, from buildings, particularly by fire rescue crew. The US Fire Administration has produced statistics showing that an estimated 2800 children aged 14 or younger are injured and 850 killed annually in residential fires. Of these children, over 40% are under the age of 5 and 70% under the age of 10.

According to standard procedures for fire rescue crew eg those adopted by the UK Fire Rescue Service, the crew, on entering a burning building, will, as a first priority, search rooms in a strictly specified order common to all buildings, eg clockwise starting from the first room on the right of the entrance. This ensures that every room is systematically searched even in difficult conditions where visibility is limited.

This invention arose from an observation that, during fires, there is an instinctive reaction, particularly in young children, to hide in their bedrooms, often under the bed or in the wardrobe or a closed space like a cupboard whilst the more able bodied will attempt to escape from the building. Children revert to a state of mind "if they cant see it it cant hurt them". Despite the best efforts of fire safety education in schools and from parents, children, particularly young children still seek safety from fires by hiding in their bedrooms. The vast majority of children killed in domestic fires are found in their bedrooms. Consequently, any room used by a child or other vulnerable person is more likely than other rooms to contain a person in need of rescue. The invention resides partly in the theory that, for the above reason, a rescue exercise that involves an initial search of rooms likely to be occupied by children or other vulnerable people is likely to improve the statistics of successful rescues.

The invention provides a system for assisting the rescue of vulnerable persons from a building comprising an internal access area and a number of rooms having doors opening onto the access area, characterised by a visual signalling unit mounted on or adjacent the door of a room identified as containing a vulnerable person, the signalling unit being designed to respond to an emergency situation by generating a visual signal, visible to rescuers in the access area.

By employing the invention, it becomes possible, in a building already fitted with one or more normal alarms, to identify to rescuers the rooms that are most likely to contain a person in need of rescue. The standard procedures of rescue crews can then be modified so that these rooms are always searched first.

Each visual signalling unit is preferably designed to respond to the sound of a smoke alarm. There may be such a smoke alarm just at selected positions in the building eg in a kitchen area, where a fire is most likely to start; or there may be a smoke alarm in each room. Alternatively, the visual signalling unit may be designed to respond to other types of alarm signal. For example the sound of a carbon monoxide alarm, the sound of a fire alarm, it may be hard wired into an alarm system. Another option is for the signalling unit to be designed to respond to an ultrasonic or radio signal. An advantage of this is that such a signal can be encoded so as to eliminate any possibility of false alarms. A disadvantage, however, is that such a system could not be used with standard smoke alarms without modification to the latter.

In buildings such as hotels it may be convenient for visual signalling units to be mounted on or alongside the doors of all guest rooms and to be designed to be activated or deactivated depending on occupancy. The activation or deactivation may be performed by a central control unit at a reception area. When a vulnerable person checks in at the hotel he/she can be allocated a room and the associated unit activated at the same time. Existing infrastructure currently used for key and lock activation may be used for this purpose.

In implementing the invention there is a serious problem of avoiding actuation of the signalling unit by sounds similar to a smoke alarm such as bird song or music. There can also be a problem arising from actuation of the unit when the smoke alarm is temporarily actuated in a situation that is not a true emergency eg in response to a minor incident which can quickly be fixed, such as burning toast. A preferred feature of the invention avoids these problems in a particularly effective manner that will now be described.

The UK Fire and Rescue Service (which is typical of similar services worldwide) estimates that the minimum response time between receipt of a call for help and arrival at the scene of a fire is 4 minutes in an average urban location. In remote locations it may be very much longer. The inventors have realised that, because their invention is intended to assist a professional rescuer to find a potential victim, the whole of this 4 minute time period (with a margin for error) is available for observing and analysing the sound of the smoke alarm to avoid false triggering by other sounds.

This contrasts with known sound activated flasher units that are designed to be activated immediately after activation of a smoke alarm for the purpose of indicating exit and entry point to the building. Therefore, a preferred feature of the invention is that the sound from the smoke alarm is observed for as long as is necessary (up to a limit of 4 minutes) in order to be as sure as possible of avoiding false actuations or actuations arising from minor incidents such as the burning toast scenario referred to earlier. A period of at least 15 and preferably 30 seconds is preferred because it has been found that few extraneous sources of sound will mimic a smoke detector consistently for a 30 second period. Better still is a period of 1, 2 or 4 minutes, which will also give sufficient time for minor incidents, that are not true emergencies, to be dealt with.

The analysis of the sound over the abovementioned long period of time can be effectively achieved by inspecting the output of a microphone during this period, and generating an indication of variations in frequency, pulse rate and/or onloff ratio in the signal. An audible signal from a smoke alarm will be highly consistent over a period of 4 minutes whilst other sounds, that might be difficult to distinguish from a smoke alarm using traditional filtering methods, are unlikely to continue without variation, for 30 seconds or more.

One way in which the invention may be performed will now be described by way of example with reference to the accompanying drawings in which: -Fig 1 is a schematic plan view of a building fitted with a system in accordance with the invention; Fig 2 is a circuit diagram of an indicator unit mounted outside one of the rooms of the building; and Fig 3 is a flow chart showing the principal operations performed by a processor indicted on Fig 2.

Referring firstly to Fig 1 there is shown a building having an outer wall 1, a number of rooms 1A to 1H and an access area A. Doors 3 open into rooms 1A to 1H respectively and a door 4, in the outer wall, opens into the access area A. Each of the rooms 1A to 1H and the access area contains a ceiling-mounted smoke detector SD of conventional construction. This is designed to emit an alarm signal in the form of a sound burst or "bleep" having a frequency of f and a duration oft1. This sound burst is repeated indefinitely with periods of to between bursts. The values of f, ti and to vary depending on manufacture. They generally use a base frequency of 2.5KHz to 3.8 KHz. Pulse rates vary from 1 to 4 Hz and the onloff ratio from 95% to 2%.

In Fig 1 it is assumed that room 1 F has been identified as being occupied by a vulnerable person. Adjacent to the door 3 of this room and visible to persons in the access area A is a visual signalling unit 5. This is designed to respond to an alarm signal from any of the smoke alarms by emitting a flashing light to direct a rescuer, on entering the access area A, directly to the room containing the most vulnerable person.

The visual signalling unit 5 comprises a housing adapted to be fixed to the wall and containing a circuit shown, in simplified form, on Fig 2. This comprises a microphone 6 comprising an off-the shelf piezoelectric device 6A, adjustable resistor 6B, capacitor 6C and resistor 6D.

The output of the microphone 6 is passed to an amplifier and filter 7 having three identical stages 7A, 7B and 7C. Each of these stages includes an OP amp such as component MCP6144 available from Microchip Technology Inc. used in a multiple feedback configuration and designed to pass frequencies within the band 2.5 to 3.8 KHz. A pair of diodes 7D between the second and third stages prevents the third stage from saturating and causing excessive demands of the battery.

The output of the amplifier 7 is passed to a square wave generator 8 comprising a capacitor 8A and a Schmitt trigger 8B. The resulting square waves, still at audio frequencies, are passed to a programmed microprocessor 9 such as component Plc i 8F24K20 of Microchip Technology Inc. The output of the amplifier 7 is also passed to a wake-up circuit 10 where it is first rectified by an arrangement of diodes 1OA and capacitors lOB and resistor 1OC. The rectified signal is then passed to a low pass filter formed by resistor 1OD and capacitor bE. When the rectified voltage, has exceeded a certain level, say 2 volts, for a significant period, say 1 second, the voltage on capacitor 1 OE becomes sufficient to operate a Schmitt trigger 1 OF, indicating the presence for that 1 second period, of a sound having a frequency consistent with that of a smoke detector. The Schmitt trigger, when triggered, switches and holds on the power from battery Bi to the microprocessor 9. When there is no detected sound, the microprocessor is switched off by the circuit 10 thereby avoiding demand on a battery B 1. The battery supplies power to each of the components 7, 8, 9 and 10 but the demand from the microprocessor 8 is the greatest.

In addition to receiving timing signals from the square wave generator 8, the microprocessor has access to a store 11 containing, for all known commercially available smoke alarms, information defining i) the range of average audio frequencies, ii) the range of periods between the start of any one burst and the start of the next burst, and iii) the range of onloff ratios. It is programmed to perform a logical operation which will be described later with reference to Fig 3 and to produce a pulsing output (of 0.5 Hz with an onlof ratio of 2/7) only when it has detected a consistent pattern of input signals for a period of one minute.

The output from the microprocessor is fed to an LED driver circuit 12 powered, in this particular example, from a separate battery B2, to drive an LED 12A. After a rescue operation, the system is re-set using a reset switch RS connected to the processor.

Referring now to Fig 3, when the processor 9 has been switched on by the wake-up circuit 10, a real time clock 13 generates interrupt signals at times T1, T2, T3 etc, defining time slots between them. In this example, each time slot is 20 ms. The square wave generator 8 of Fig 2, also shown on Fig 3, produces bursts of square waves corresponding to the bursts of noise detected from the smoke alarm that has activated the wake-up circuit. During each time slot, the zero crossing points (two for each cycle of the square waves) are counted and stored at 14. At 15, the count for each time slot, representing the instantaneous frequency of the input signal, is compared with a set range of counts which are known to be generated if the detect sound has emanated from commercially available smoke alarms. In this example, the set range of counts is 100 to 200, corresponding to smoke alarm frequencies of 2 to 4 KHz.

If the incremental count derived at 15 is outside the set range, it is assumed that the current burst of sound or "bleep" has finished and the finishing time, eg T is recorded at 16. When an incremental count within the set range is next detected, it is assumed that a new burst of sound has started and the start time is, eg Tn+1, is recorded at 17. The count values from 14 and the burst start and ending times from 17 and 16 respectively, are processed at 18 to derive, for each burst and subsequent period of silence: i) the average frequency of the burst, ii) the period of the burst, and iii) the onloff ratio. These values are all compared at 19 with ranges of corresponding values for known smoke alarms stored at 10. These ranges of values need to be wide because of the wide differences between different alarms. For example value i) may be specified as being within a range of 2 to 4 KHz; value ii) between 0.5 to 2 seconds; and value iii) 95% to 50%. If no match is found the power to the processor 8 is switched off.

In an alternative arrangement, the store 10 contains specified values i), ii) and iii) for every known make and model of smoke alarm. Although it is still necessary to have a margin for error in the comparison process, this margin does not have to be as wide as the ranges used to cover all alarms. However, a problem with that alternative is that resetting of the store would be needed whenever a new alarm is marketed.

If a match is found, a step is performed at 20 to test for consistency of the values i), ii) and iii) over the time since the wake-up circuit 9 switched on the processor. If the values are all found to match within a specified tolerance (in this example 10%), a score, held in a register 21 is incremented by 1. If any one of these values are found to have varied by more than the specified tolerance, the register is decremented by an amount greater than 1. In this particular example it is decremented by 3. In this way, the register 21 contains a measure of the consistency of the sensed sound. This is important because, although different smoke alarms have a wide variety of different sounds depending on make and model, they can all be relied upon to be highly consistent over a long period of time.

If the score held in register 21 reaches zero (it is not permitted to be less than zero), this is detected at 22 and the power to the processor 9 is switched off If the score reaches a value corresponding to a 2 minutes of processor switch-on time (in alternative embodiments this could be up to 4 minutes), this is detected at 23, causing a strobe circuit 42 to produce a pulsed output to the LED driver circuit 11 before the fire crew arrive at the scene of the fire.

The embodiment of the invention that has been described is particularly effective and reliable because it employs, for processing, at least a substantial proportion of the minimum time taken for a fire crew to respond and arrive and because it examines the signal for consistency of the parameters referred to by references i), ii) and iii) above rather than the more obvious choice of relying on instantaneous measurements of frequency etc. Many variations to the described arrangement are possible within the scope of the invention as defined by the accompanying Claims. For example, the store 10 could be loaded with values i), ii) and iii) for every known make and model of smoke alarm.

Although it would still necessary to have a margin for error in the comparison process 37, this margin does not have to be as wide as the ranges used to cover all alarms.

However, a problem with that alternative is that resetting of the store would be needed whenever a new alarm is marketed.

In another variation, the one minute time period during which processing takes place and the one second timing period of the wake-up circuit 9 could be varied. Another possible variation would be to arrange the microprocessor to switch on the amplifier 6 only intermittently. In theory, it would need to be switched on for just one second (sufficient for the wake-up circuit to respond) each 4 minutes (the minimum time taken for a fire rescue crew to arrive, though in practice some good margins for error are desirable. Although the invention is thought to be most likely to be employed in relation to fire emergencies, it is equally applicable to emergencies associated with dangerous heat levels (without combustion) and emergencies associated with dangerous gasses.

Claims (13)

1. Claims 1. A system for assisting the rescue of vulnerable persons from a building comprising an internal access area and a number of rooms having doors opening onto the access area, characterised by a visual signalling unit mounted on or adjacent the door of a room identified as containing a vulnerable person, the signalling unit being designed to respond to an emergency situation by generating a visual signal, visible to rescuers in the access area.
2. 2. A system according to Claim 1 characterised by at least one alarm designed to generate an alarm signal in an emergency situation, the signalling unit being designed to respond to the alarm.
3. 3. A system according to Claim 2 characterised in that the alarm is an audible alarm.
4. 4. A system according to Claim 2 characterised in that the alarm is an ultrasonic alarm signal.
5. 5. A system according to Claim 2 characterised in that the alarm is a radio alarm signal.
6. 6. A system according to Claim 2, 3, 4 or 5 characterised in that the signalling unit comprises a processor adapted to examine an alarm signal for consistency over a time period.
7. 7. A system according to Claim 6 characterised in that the time period is at least seconds.
8. 8. A system according to Claim 7 characterised in that the time period is at least seconds.

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9. 9. A system according to Claim 8 characterised in that the time period is at least 1 minute.
10. 10. A system according to Claim 9 characterised in that the time period is at least 2 minutes.
11. 11. A system according to Claim 3 or 4 or any of Claims any of Claims 6 to 10 when dependent on Claim 3 or 4 characterised in that the signalling unit comprises a microphone and means for examining a property of a signal derived from the microphone for consistency during the said time period.
12. 12. A system according to Claim 2 comprising two or more of the said visual signalling units mounted adjacent respective doors, a control unit, means by which the control unit can communicate with the signalling units to selectively activate them to be responsive to the emergency situation.
13. 13. A visual signalling unit for use in a system according to any preceding Claim Amendments to claims have been filed as follows 1. A system arranged to assist the rescue of vulnerable persons from a building comprising an internal access area and a number of rooms having doors opening onto the access area, characterised by a visual signalling unit mounted on or adjacent the door of a room identified as containing a vulnerable person and visible to persons in the access area, the signalling unit comprising: a microphone; means for processing an output of the microphone so as to identify a sound emanated from an alarm; and means for generating, in response to such detection, a visual signal, visible to rescuers in the access area.2. A system according to Claim 1 characterised by at least one alarm designed to generate an audible alarm signal in an emergency situation, the alarm being Q positioned at a position in the building selected as being where a fire is most likely to start, the signalling unit being designed to respond to the audible Cv') 15 alarm.If) 3. A system according to Claim 1 or 2, characterised in that the signalling unit comprises a store for defining at least one characteristic of an alarm signal a processor adapted to compare the output of the microphone with the content of the store.4. A system according to Claim 1, 2 or 3, characterised by means to indicate whether the output of the microphone is consistent with a known characteristic of an alarm signal over a period of at least 15 seconds and in response to such indication to cause the visual signal to be generated..5. A system according to Claim 4 characterised in that the time period is at least 30 seconds.6. A system according to Claim 5 characterised in that the time period is at least 1 minute.7. A system according to Claim 6 characterised in that the time period is at least 2 minutes.8. A system according to Claim 3, 4, 5, 6 or 7 characterised in that the processor is adapted to compare the frequency of an audio frequency signal from the microphone with a value or values held in the store.9. A system according to Claim 3, 4, 5, 6, 7 or 8 characterised in that the processor is adapted to compare the periods of bursts of an audio frequency signal from the microphone with a value or values held in the store.10. A system according to Claim 3, 4, 5, 6, 7, 8 or 9 characterised in that the processor is adapted to compare the onloff ratio of bursts of an audio frequency signal from the microphone with a value or values held in the store.11. A system according to any preceding Claim comprising two or more of the CY) said visual signalling units moimted adjacent respective doors, a confrol unit, 0 means by which the control unit can communicate with the signalling units to If) 15 selectively activate them.12. A visual signalling unit for use in a system according to any preceding Claim