Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B17/00—Fire alarms; Alarms responsive to explosion
  • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B17/00—Fire alarms; Alarms responsive to explosion
  • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
  • G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas

Definitions

• the heat detectors are, which is implicit in this term, dependent thereon that -they have to be ' subjected to a certain minimum heat influence in order to release a signal, and when in a living-room a fire has been able to develop so far that heat detectors will give a warning signal, it will as a rule be too late to save the life of persons who are still within the living-room wherein the fire has developed.
• smoke detectors may be activated so early by a starting fire that persons may be rescued.
• the alarm from such detectors will bereleased when the detectors are subjected to a certain minimum smoke influence, and this means that warning of the fire may take place when the fire is still in the smouldering stage.
• the smoke detectors currently used are of the optical type or of the ionic type.
• the optical smoke detectors will be more rapidly activated by a smouldering fire whereas the ionic smoke detectors will be activated at a markedly later stage and perhaps firstly when the smouldering fire has changed into a fire with open flame. Accordingly, due to early warning of a smouldering fire the so called optical smoke detectors ought to be able to be used with the greatest advantage, however, these smoke detectors will often be so sensitive that they may easily cause false warning like e.g. when the living-room has a high concentration of tobacco smoke.
• the ionic smoke detectors are the ones which have been most thoroughly tested and are most secure in operation and lead to least false warning, however, as mentioned they will be activated at a later stage than the optical smoke warners under otherwise equal conditions. Experiments have shown that under like conditions in living-rooms wherein smouldering fire has been intentionally initiated it will take about 3 times longer to activate an ionic smoke detector than to activate an optical smoke detector.
• a fire warning system which comprises use of an ionic smoke detector,the system being characterized therein that the ionic smoke detector is used in living-rooms which are ventilated by means of diffuse air supply.
• the main principle by conventional ventilation of living-rooms is the so called mixing ventilation, i.e. with the same temperature and air quality being created in the entire room. This means that contaminations, like tobacco smoke, heat or odour etc., are mixed and uniformally distributed throughout the room.
• the so called diffuse ventilation is based on another principle. By diffuse ventilation the ventilation air is introduced at floor level, and the used air in the room will be discplaced by the ventilation air introduced and be sucked out at ceiling level Diffuse air supply is based thereon that fresh air is supplied at low level in the occupation zone at very low velocity and with uniform distribution of the introduced air. This is introduced with a slightly lower temperature than the room air and utilizes the law of nature that warm air is ascending. Accordingly, the contaminations in the room ventilated by diffuse air supply will be brought up to the ceiling and be withdrawn at ceiling level without the contaminations being stirred around in the living-room.
• the present invention is based on the recognition that by the combination of diffuse air supply for ventilation of living-rooms and ionic smoke detector the latter may be influenced earlier by a higher and alarm-releasing smoke concentration in cases of fire than when using no ventilation or normal mixing ventilation of living-rooms, because the diffuse air supply, as mentione will cause the contaminations, i.e. in this case the smoke, in the living-room to be brought up to the ceiling and. there influence the ionic ' smoke detector and put it into.action.
• the additional advantage is obtained by the system according to the invention that because the contaminations rapidly are brought up towards the ceiling when using diffuse air supply the risk that persons staying in the room will be poisoned by smoke will be strongly reduced, and concurrently the free sight will be better maintained in the room with smouldering fire and make it easier for people to find and rescue persons . staying in the room. . .
• the ionic smoke detector may then be arranged in the ceiling or in the channel at ceiling level for carrying off the used room air, and due to the high concentration of smoke which is rapidly ' obtained at ceiling level when using diffuse air supply to the room in which the smouldering fire occurs, the rapidlyreleased signal from the smoke detector can be used for controlling the supply of air to the room in order to increase the height of the stratum in the room, i.e. the height of the stratum wherein the concentration of smoke is relatively low.
• the strength of the signal from the ionic smoke detector is dependent upon the concentration of the smoke, and it is thereby possible to obtain an automatic control of the amount of ventilation air supplied in dependence of the concentration of the smoke detected by the ionic smoke detector.
• a such circuit for the control of the amount of air consists of a control flap in the ventilation air channel from which ventilation .air is supplied into the ventilation air distributing means in the room, a control motor, an air stream regulator and an air stream measuring device.
• the air stream regulator will continuouslymeasure the air stream in the ventilation air channel in relation to the amount of ventilation air indicated by the strength of the signal from the ionic smoke detector, and if these air stream values are different from one another the regulator will by means of the control motor automatically influence the position of the flap in the ventilation air channel so that the stream of ventilation air will be proportioned to the strength of the signal given off by the ionic smoke detector.
• a suitable apparatus for fulfilling this function is the apparatus which is sold under the trade name "OPTIVENT ⁇ VAV Ter inalapparat” and delivered by Flakt AB, Sweden. A sketch showing the principles of a such solution is shown in the drawing.
• the drawing shows a section of a ventilation air channel 1 through which ventilation air flows in the direction of the arrow.
• a controllable flap 2 is arranged, and the position of the flap is influenced by a flap control motor 3 which receives a command signal from an air stream regulator 4 which continuously measures the stream of ventilation air at 5 in the ventilation air channel 1.
• the air stream regulator 4 is electrically connected to an ionic smoke detector 6 which gives signals to the air stream regulator, the strength of the signal being dependent upon the concentration of the smoke * detected at the place the smoke detector is positioned.
• the air stream regulator 4 is supplied with pneumatic or electric power from a corresponding source 7, and if the air stream measured by the air .stream regulator 4 does not correspond to the air stream dictated by the electrical signal from the ionic smoke detector 6 the air stream regulator 4 will through the flap control motor 3 automatically change the position of the flap 2 in the ventilation air channel 1 so that the amount of ventilation air into the ventilated room at floor level will increase proportionally with the strength of the signal from the ionic smoke detector 6.
• the advantages of a such system are obvious.
• the ionic smoke detector will at a certain minimum concentration of the smoke at the place where the ionic smoke detector is positioned react spontaneously thereto and give off a signal to the air stream regulator 4 which will then automatically through the flap control motor 3 control the position of the flap 2 in the ventilation air channel 1 so that an increased amount of ventilation air will be introduced into the room wherein the smouldering fire occurs and causing .an increased stream of ventilation air into the room in order to displace the developed smoke up towards, ceiling level.
• the electrical signal from the ionic smoke detector may also be utilized for continuously controlling the amount of ventilation air and release an alarm firstly at a pre ⁇ determined concentration of smoke. Thus, prior to the release of the alarm the system will all the time be functioning and improve the air conditions in the room by controlling the amount of air.

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• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Fire Alarms (AREA)
• Fire-Detection Mechanisms (AREA)
• Alarm Systems (AREA)

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Publications (1)

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• 1985
  • 1985-02-08 NO NO850482A patent/NO158391C/no not_active IP Right Cessation
• 1986
  • 1986-02-07 WO PCT/NO1986/000013 patent/WO1986004708A1/en unknown
  • 1986-02-07 EP EP19860901146 patent/EP0211885A1/de not_active Withdrawn
  • 1986-02-07 AU AU53947/86A patent/AU5394786A/en not_active Abandoned

Non-Patent Citations (1)

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