WO1993008550A1 - Fire detector and a method of detecting a fire - Google Patents
Fire detector and a method of detecting a fire Download PDFInfo
- Publication number
- WO1993008550A1 WO1993008550A1 PCT/GB1992/001964 GB9201964W WO9308550A1 WO 1993008550 A1 WO1993008550 A1 WO 1993008550A1 GB 9201964 W GB9201964 W GB 9201964W WO 9308550 A1 WO9308550 A1 WO 9308550A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- fire
- sensor
- changes
- transducer means
- fire detector
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
- G08B29/18—Prevention or correction of operating errors
- G08B29/183—Single detectors using dual technologies
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0062—General constructional details of gas analysers, e.g. portable test equipment concerning the measuring method, e.g. intermittent, or the display, e.g. digital
- G01N33/0063—General constructional details of gas analysers, e.g. portable test equipment concerning the measuring method, e.g. intermittent, or the display, e.g. digital using a threshold to release an alarm or displaying means
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B17/00—Fire alarms; Alarms responsive to explosion
-
- 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
- G08B17/117—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means by using a detection device for specific gases, e.g. combustion products, produced by the fire
Definitions
- This invention relates to fire detectors of the kind having transducer means, and capable of giving a reaction at ambient temperatures to changes in an 5 atmospheric condition characteristic of the presence of combustion, with the transducer means being arranged to give an electrical output signal representing its response to the said changes.
- a fire detector will be referred to as a fire detector of the kind 10 specified.
- the sensors are of the impregnated semiconductor type which react to a change in the concentration of carbon monoxide in the atmosphere by a change in their electrical resistance.
- a fire variously produces gases (particularly carbon monoxide, and also, commonly, hydrogen) , and smoke.
- Water vapour is often produced by combustion of hydrogenous matter such as hydrocarbons.
- the extent to which any one of these factors is present to any significant, or easily-detectable, extent will vary according to the circumstances. This is especially so in the very early stages of a fire when, of course, it is most desirable that the fire be detected: the factor that is predominant at that time should be detected regardless of which factor it happens to be.
- Sensors of the impregnated semiconductor resistor type for sensing changes in CO concentration are essentially chemical in function, albeit producing a physical effect in the form of an electrical signal representing the resistance of the sensor. It is known to be desirable to be able to diagnose a fire chemically, using sensors with suitable characteristics, with a view to avoiding the disadvantages of fire detectors that rely on purely physical principles as mentioned above .
- the characteristics which are important for fire sensors employing chemical principles include robustness against poisons in the air, sensitivity to gases given off in typical fires, very low power consumpton, small size and low cost. While some of these characteristics are present in the general type of sensor described in the above-mentioned paper of Harwood et al, the known art of fire detection using such a sensor still envisages a sensor dedicated to the detection of a single effect characteristic of combustion, e.g. CO concentration. To detect any other effect (such as temperature) , it has been thought that separate sensing means would be essential.
- Sensors of porous tin dioxide, impregnated with at least one noble metal deposited on the surface of its pores and capable of giving a reaction at ambient temperatures to changes in the concentrations of particular gases in the atmosphere, and methods of making them, are variously described in the documents GB 2 249 179A and GB 2 248 306A, and in our co-pending United Kingdom patent application No. 92 126 507.
- a tin dioxide sensor element is impregnated with platinum and an additive which increases its selective sensitivity to the presence of atmospheric hydrogen, by increasing its density.
- a tin dioxide resistor for use as a transducer or sensor element is impregnated with at least one phase of a metal such that the electrical resistance of the sensor is a function of the concentration of a given gas in the atmosphere in such a way that its sensitivity to that gas in trace quantities is reduced, but its sensitivity to the same gas is not impaired at the higher concentrations at which the sensor is most useful.
- Application No. 92 126 507 describes a resistor sensitive to CO in which its response at ambient temperatures is improved by including in its manufacturing process a heat treatment stage to increase its electrical resistance, after deposition of metallic particles on the surface of the pores.
- An object of the present invention is to provide a fire detector of the kind specified which has all the characteristics mentioned above for sensors using chemical principles, and which, in addition, is able to detect a fire without relying on any one effect of combustion.
- Another object is to achieve this with a single transducer means.
- a fire detector of the kind specified is characterised in that the transducer means is such as to give a simultaneous response to changes in a plurality of atmospheric conditions characteristic of the presence of combustion, whereby its output signal represents all of the said changes.
- the transducer means is such that its said simultaneous response is to an increase, in the atmosphere, of at least: carbon monoxide concentration; water content; and temperature.
- the transducer means in such a fire detector the transducer means consists of a single semiconductor resistor, which is preferably also responsive to an increase in hydrogen concentration in the atmosphere.
- Such a sensor responds unambiguously to these indicators, so that it is in effect a plurality of sensors of different combustion effects combined in a single element. Since its response to every one of these effects is a reduction in its resistance, any decrease in resistance can be taken as a reliable indication that a fire is likely to be present.
- a method of detecting a fire using a transducer means comprising a sensor of semiconductor material impregnated with at least one noble metal and capable of giving a reaction at ambient temperatures to changes in an atmospheric condition characteristic of the presence of combustion, the method including receiving and processing the output signal from the transducer means to produce an alarm signal representing its response to the said changes, is characterised in that it includes receiving and processing the output signal simultaneously representing changes in a plurality of conditions characteristic of the presence of combustion.
- Figure 1 is a graph showing a typical characteristic curve for resistance of the sensor with atmospheric concentration of CO;
- Figure 2 is a graph showing a typical characteristic curve for variation of the resistance of the sensor with atmospheric temperature
- Figures 3 and 4 are diagrams of resistance plotted against time, showing reductions in the resistance of the sensor on introduction to CO and hydrogen respectively;
- Figure 5 is a diagram of resistance plotted against time, showing the effect on the former of the occurrence of short introductions of water vapour into the atmosphere;
- Figure 6 is a graph showing the effect of carbon monoxide on the rate of change of resistance of the sensor, in particular in regard to the initial response rate of the latter;
- Figure 7 shows diagra matically a fire detector according to the invention in which the transducer means is in the form of an array of sensors.
- the fire detector in this example is part of a fire protection system comprising one fire detector, or a number of fire detectors (all of which may be substantially identical) located in suitable positions in or on a building or other fixed structure.
- the system may equally be installed in a ship, aircraft or other vehicle.
- the system typically includes, in the usual way, a power supply and suitable signal processing means for receiving electrical output signals from the detector, or from each of the detectors, and for processing those signals so as to produce an alarm signal in response to these output signals.
- the alarm signal is produced when a fire detector gives an output signal indicating that combustion is present, and typically consists of one or more audible and/or visual signals, with or without other functions such as causing fire doors to close automatically, activating a sprinkler system, and so on.
- the fire detector itself consists of a single transducer element exposed to the atmosphere and suitably mounted, e.g. on an insulating substrate within a protective housing, with an electrical connection to the signal processor whereby a voltage is applied to the transducer.
- the transducer element (referred to from here on as the sensor) is a semiconductor resistor, of porous semiconductor material (Sn ⁇ 2 in this example) having at least one noble metal, such as Pt or Pd, impregnated into it so as to be deposited on the surface of its pores.
- the sensor is one that is capable of giving a reaction at ambient temperatures, typically in the range 3 - 50°C, though it should also be capable of giving a reaction at the higher temperature to be expected in the presence of a fire.
- the reaction referred to above is a reaction to changes in an atmospheric condition characteristic of the presence of combustion, and consists in a reduction in the electrical resistance of the sensor so that the electrical output signal from the sensor is manifested as an increase in current through the sensor, received and processed accordingly by the processor.
- the senor is so made that it reacts in this way to an increase in any one or more of at least three parameters indicative that combustion is likely to be present, namely:
- the processor is preferably programmed in such a way as to ignore output signals from the detector resulting from increases in these parameters due to the variations which are to be expected under normal conditions in the environment being protected by the system. Thus for example it might be so arranged that the alarm signal is not initiated when: (a) there is an increase in only one of the parameters, this remaining below a predetermined threshold value; or
- the sensitivity of the sensor to each of the detectable parameters, and other characteristics of the sensor, will be determined during the manufacturing process, for example by appropriate addition of additives or by use of an additional heat treatment step.
- the sensor may for instance be of any of the kinds described in the above-mentioned documents GB 2 249 179A,
- Figures 1 to 6 illustrate the behaviour of a typical sensor for a fire detector according to the invention.
- Figure 1 shows how its resistance R decreases with increasing CO concentration in dry air
- Figure 2 is a characteristic curve showing how R varies with temperature T.
- Figures 3 and 4 show how R varied over a period of time t in two experiments in which, at.5 minutes, CO and H2 respectively were rapidly introduced into an air atmosphere, being flushed away rapidly starting at 10 minutes.
- the concentration of each gas was ⁇ %.
- Figure 5 shows the curve of variation in R with time t during an experiment in an atmosphere consisting of air at 15% relative humidity.
- a 1% concentration of CO was introduced rapidly at times t , t3 and -t ⁇ , and then flushed away rapidly.
- Momentary pulses of water vapour were introduced rapidly at times t-j , t2, , t5 and X. .
- the resulting brief decreases in R showed in the pulses indicated at P.
- the resistance of the sensor is significantly reduced very rapidly in response to an increase in any one of the four detected parameters, independently of any of the others. Accordingly, if more than one parameter increases , the reduction in resistance is cumulative, i.e. the output signal is enhanced, so that an increase in any parameter cannot tend to cancel the effect due to an increase in any other parameter. Consequently, the sensor is a reliable means for detecting the possibility of fire in response to any or all of the parameters discussed.
- the detector preferably comprises a single sensor as described above. However, within the scope of the invention it may comprise an array consisting of a number of individual sensors, each dedicated primarily (though not necessarily exclusively) to the sensing of a specific one of the parameters which are to be detected. Thus such an array consists, for example and as shown in Figure 7 , of a gas sensor 10 for detecting changes in CO concentration, together with a heat sensor 12 for detecting temperature changes, and/or a humidity sensor 14.
- the heat sensor reacting to increases in temperature due to a fire, provides corroboration of the signals from the gas and humidity sensors. In addition, it permits correction of, or allowance to be made for, a pre-determined extent of cross-sensitivity to heat rises by the gas sensor.
- Such cross-sensitivity being an essentially constant factor in any particular type of gas sensor, can be readily pre-established by calibration.
- the humidity sensor likewise provides corroboration for the signals of the gas and heat sensors by detecting the humidity increases associated with a fire, while again allowing compensation to be made for the pre- determined cross-sensitivity of the gas sensor to humidity.
- An array 20 comprising at least one such gas sensor element 10 ( Figure 7), together with at least one, or preferably both, of the heat and humidity sensors 12, 14, is connected to the signal processing means 18, which is arranged so as to initiate the alarm signal 2 only when the output signal from the gas sensor 10 is corroborated and corrected where necessary for cross- sensitivity, by the heat sensor 12 and/or the humidity sensor 14.
- the extent of cross-sensitivities to both temperature and humidity is low in the preferred types of gas sensor described, in relation to the response to gaseous emanations, in particular those of CO.
- a further gas sensor 16, responsive to hydrogen concentration, may of course be included in the array.
- the CO sensor 10 is preferably of the type based on S ⁇ 2 impregnated with Pt or Pd, including devices of the general type described in the document GB 2 249 179A.
- Such sensors can be produced so as to exhibit high sensitivity to CO with relatively low cross- sensitivity to moisture and heat, and in this embodiment they are of the kind operable at ambient temperatures in the manner discussed earlier herein.
- heat sensors 12 can be used, preferred elements being those based on electrical resistors with numerically high temperature coefficients of resistance, including those known by the Trade Mark THERMISTOR. Examples of preferred types are based on resistor bodies of oxide ceramics, e.g. having a spinel crystal structure. Other such resistors are based on SiC, Pt, etc.
- Various conventional types of humidity sensors 14 may be used. Preferred types are those relying either on changes in resistance or capacitance in response to humidity effects in resistors or capacitors, e.g. with porous titanate ceramic dielectrics respectively.
- the single sensor, or the sensors in array, of a fire detector according to the invention may be deposited or otherwise carried upon a mother plate 22, being for example silk-screen printed on a ceramic, e.g. alumina, substrate.
- fire detectors according to the invention preferably comprise elements all of which are unheated, and which thus require very low power supplies.
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP92922567A EP0609354A1 (en) | 1991-10-24 | 1992-10-26 | Fire detector and a method of detecting a fire |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB919122622A GB9122622D0 (en) | 1991-10-24 | 1991-10-24 | Fire detectors |
GB9122622.5 | 1991-10-24 | ||
GB9212650.7 | 1992-06-15 | ||
GB929212650A GB9212650D0 (en) | 1992-06-15 | 1992-06-15 | Transducer elements |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1993008550A1 true WO1993008550A1 (en) | 1993-04-29 |
Family
ID=26299736
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1992/001964 WO1993008550A1 (en) | 1991-10-24 | 1992-10-26 | Fire detector and a method of detecting a fire |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0609354A1 (en) |
WO (1) | WO1993008550A1 (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5629474A (en) * | 1993-03-30 | 1997-05-13 | Keele University | Production of a sensor for carbon monoxide or water vapor including a semi conductor metallic oxide, catalyst, and rheological agent |
EP0940679A2 (en) * | 1998-03-02 | 1999-09-08 | SIEMENS MATSUSHITA COMPONENTS GmbH & CO. KG | System for fire detection and method and sensor especially for this system |
DE4333060C2 (en) * | 1993-09-29 | 2002-11-07 | Joachim Hahne | Process for maintaining the operational safety of a ship and arrangement for carrying out the process |
DE19845553C2 (en) * | 1998-10-02 | 2003-10-16 | Bosch Gmbh Robert | fire alarm |
EP2083405A1 (en) | 2008-01-24 | 2009-07-29 | S + G Messtechnik GmbH | Fire alarm |
US8248253B2 (en) | 2008-04-21 | 2012-08-21 | Honeywell International Inc. | Fire detector incorporating a gas sensor |
DE102011122119A1 (en) * | 2011-03-25 | 2012-09-27 | Odb-Tec Gmbh & Co. Kg | Thin film diode arrangement for hydrogen sensor in hydrogen-powered vehicle, has sponge-like porous structure and corresponding porous structure formed on titanium oxide layer and metal layer, respectively |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3245067A (en) * | 1963-05-24 | 1966-04-05 | B R K Electronics Inc | Detection of products of combustion |
GB1280297A (en) * | 1968-11-13 | 1972-07-05 | Brk Electronics | Improvements in and relating to combustion detectors |
DE2428488B2 (en) * | 1973-06-12 | 1978-11-23 | Nohmi Bosai Kogyo Co., Ltd., Tokio | Device for the detection of carbon monoxide and method for its production and its use |
DE3640734A1 (en) * | 1986-11-28 | 1988-06-09 | Heinz Hoelter | Sensor with electronic humidity and temperature correction |
DE3123279C2 (en) * | 1981-06-12 | 1990-12-20 | Westfaelische Berggewerkschaftskasse, 4630 Bochum, De |
-
1992
- 1992-10-26 WO PCT/GB1992/001964 patent/WO1993008550A1/en not_active Application Discontinuation
- 1992-10-26 EP EP92922567A patent/EP0609354A1/en not_active Withdrawn
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3245067A (en) * | 1963-05-24 | 1966-04-05 | B R K Electronics Inc | Detection of products of combustion |
GB1280297A (en) * | 1968-11-13 | 1972-07-05 | Brk Electronics | Improvements in and relating to combustion detectors |
DE2428488B2 (en) * | 1973-06-12 | 1978-11-23 | Nohmi Bosai Kogyo Co., Ltd., Tokio | Device for the detection of carbon monoxide and method for its production and its use |
DE3123279C2 (en) * | 1981-06-12 | 1990-12-20 | Westfaelische Berggewerkschaftskasse, 4630 Bochum, De | |
DE3640734A1 (en) * | 1986-11-28 | 1988-06-09 | Heinz Hoelter | Sensor with electronic humidity and temperature correction |
Cited By (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5629474A (en) * | 1993-03-30 | 1997-05-13 | Keele University | Production of a sensor for carbon monoxide or water vapor including a semi conductor metallic oxide, catalyst, and rheological agent |
DE4333060C2 (en) * | 1993-09-29 | 2002-11-07 | Joachim Hahne | Process for maintaining the operational safety of a ship and arrangement for carrying out the process |
EP0940679A2 (en) * | 1998-03-02 | 1999-09-08 | SIEMENS MATSUSHITA COMPONENTS GmbH & CO. KG | System for fire detection and method and sensor especially for this system |
DE19808663A1 (en) * | 1998-03-02 | 1999-11-25 | Siemens Matsushita Components | Fire detection and operating system and sensor especially for this system |
DE19808663C2 (en) * | 1998-03-02 | 2001-05-23 | Epcos Ag | Fire detection system and operating procedures for this system |
EP0940679A3 (en) * | 1998-03-02 | 2001-06-13 | SIEMENS MATSUSHITA COMPONENTS GmbH & CO. KG | System for fire detection and method and sensor especially for this system |
DE19845553C2 (en) * | 1998-10-02 | 2003-10-16 | Bosch Gmbh Robert | fire alarm |
EP2083405A1 (en) | 2008-01-24 | 2009-07-29 | S + G Messtechnik GmbH | Fire alarm |
DE102008005821A1 (en) | 2008-01-24 | 2009-08-06 | S + G Messtechnik Gmbh | fire alarm |
DE102008005821B4 (en) * | 2008-01-24 | 2010-04-15 | Rudi Schmitt | fire alarm |
US8248253B2 (en) | 2008-04-21 | 2012-08-21 | Honeywell International Inc. | Fire detector incorporating a gas sensor |
DE102011122119A1 (en) * | 2011-03-25 | 2012-09-27 | Odb-Tec Gmbh & Co. Kg | Thin film diode arrangement for hydrogen sensor in hydrogen-powered vehicle, has sponge-like porous structure and corresponding porous structure formed on titanium oxide layer and metal layer, respectively |
Also Published As
Publication number | Publication date |
---|---|
EP0609354A1 (en) | 1994-08-10 |
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