Fire and smoke detection and control system

• US 5,945,924 A
• Filed: 07/28/1997
• Issued: 08/31/1999
• Est. Priority Date: 01/29/1996
• Status: Expired due to Fees

• Current Assignee: Engelhard Sensor Technologies, Inc. (BASF SE), GE Security Incorporated (Carrier Global Corporation), SLC Technologies, Inc. (General Electric Company), GSBS Development Corp. (SPX Corporation)
• Original Assignee: Engelhard Sensor Technologies, Inc. (BASF SE)
• Inventors: Marman, Douglas H., Peltier, Mark A., Wong, Jacob Y.
• Primary Examiner(s): Hofsass, Jeffery A.
• Assistant Examiner(s): TRIEU, VAN THANH
• Application Number:
  US08/901,723
• Time in Patent Office: 764 Days
• Field of Search: 340/628, 340/630, 340/632, 340/522, 340/578, 340/521
• US Class Current: 340/928
• CPC Class Codes: G08B 17/10 Actuation by presence of smoke or gases , e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
• CPC Class Codes: G08B 17/113 Constructional details
• CPC Class Codes: G08B 17/117 by using a detection device for specific gases, e.g. combustion products, produced by the fire G08B17/103, G08B17/11 take precedence
• CPC Class Codes: G08B 29/16 Security signalling or alarm systems, e.g. redundant systems
• CPC Class Codes: G08B 29/183 Single detectors using dual technologies G08B13/1672, G08B13/2448, G08B13/2494 take precedence
• CPC Class Codes: G08B 29/20 Calibration, including self-calibrating arrangements

Abstract

A fire detection system combines a CO₂ gas detector with a smoke detector. Logic circuitry combines the outputs of both detectors to minimize false alarms and provide a rapid response time. In a preferred embodiment the need for periodic cleaning is reduced. In a further preferred embodiment, two alarms indicative of two different types of fires, for example flaming fires and nonflaming fires are available. A map of flaming fire and smoke may be assembled by the system to guide the firefighters. In a yet another preferred embodiment, a tentative fire alarm indication disables a local air conditioning system thereby helping to isolate and control any existing fire.

Claims

1. In a fire detection system that includes a light reflection type smoke detector having a light emitter from which light propagates along a propagation path and a light sensor positioned at an angular offset relative to the propagation path, the light sensor receiving light emitted by the light emitter and reflected by smoke particles passing across the propagation path, and the angular offset being of greater measure for optimal detection of smoke particles produced by a flaming fire than that for optimal detection of smoke particles produced by a nonflaming fire, a method of providing a fire detection system that is capable of accurately detecting flaming and nonflaming fires in a spatial region, comprising:

fixing the angular offset of the light reflecting type smoke detector to a relatively small angle for detecting and producing a first signal representative of a smoke particle concentration produced by a nonflaming fire;

providing a carbon dioxide (CO₂) detector for detecting and producing a second signal representative of a CO₂ concentration produced by a flaming fire; and

applying the first and second signals to processing circuitry that processes the first and second signals to determine whether either a flaming or a nonflaming fire condition is present in the spatial region and to produce an alarm signal in response to a determination of the presence of either condition.

2. The method of claim 1 in which the angular offset for optimal detection of smoke particles produced by a flaming fire is about 60°

and the angular offset fixed is substantially less than 60°

.

3. The method of claim 2 in which the angular offset fixed is about 30°

.

4. The method of claim 1 in which the processing circuitry includes a microprocessor and the first and second signals are applied in digital form to the microprocessor.

5. The method of claim 1 in which processing circuitry calculates a rate of change of CO₂ concentration and generates the alarm signal whenever the processor circuitry calculates that the rate of change of CO₂ concentration exceeds a predetermined amount and after which within a predetermined time the first signal indicates a smoke particle concentration greater than a predetermined level.

6. The method of claim 5 in which the predetermined time exceeds 20 seconds.

7. The method of claim 5 in which the predetermined level of smoke particle concentration is between about 0.1% per foot and 4% per foot and the predetermined time does not exceed about 15 minutes.

8. The method of claim 5 in which in which the predetermined level of smoke particle concentration is between about 0.1% per foot and 4% per foot and the predetermined amount of rate of increase of CO₂ concentration is between about 30 ppm/min and 500 ppm/min.

9. A method of distinguishing aberrant light source operation from changes in smoke or CO₂ concentration levels measured by a fire detection system including a smoke detector and a CO₂ detector, comprising:

providing a smoke detector having a light detector that detects light within a first wavelength range to produce a first signal representative of smoke concentration in a spatial region;

providing a CO₂ detector having a light detector that detects light within a second wavelength range to produce a second signal representative of CO₂ concentration in the spatial region;

operatively associating with the smoke detector and the CO₂ detector a light source that emits light within an emission wavelength range encompassing at least a portion of each of the first and second wavelength ranges; and

processing the first and second signals to detect the existence of aberrant light source operation by determining whether the first and second signals represent contemporaneous instances of mutual diminution of intensity of light incident on the smoke and CO₂ detectors.

10. The method of claim 9 in which the first wavelength range covers wavelengths of visible light and the second wavelength range covers wavelengths of infrared light.

11. The method of claim 9, further comprising providing an indication whenever the processing detects that light source failure is a cause of aberrant light source operation.

12. The method of claim 9 in which the processing includes adjusting the first and second signals in accordance with their ratio to mutually correct and thereby render them independent of variations in light source intensity.

13. A fire detection system having a prolonged operational lifetime, comprising:

a photoelectric smoke detector producing a first signal representing a measured concentration of smoke in a spatial region in which there is an actual concentration of smoke, the photoelectric smoke detector having an alarm threshold value representing a predetermined concentration of smoke;

correction circuitry that offsets the first signal by a drift tolerance amount to produce a corrected first signal that more accurately represents the actual concentration of smoke in the spatial region;

a CO₂ detector producing a second signal representing a concentration of CO₂ in the spatial region; and

either one of the corrected first signal or the second signal causing production of an alarm signal whenever any member criterion of a predetermined set of criteria is satisfied, one member criterion in the predetermined set including a condition in which the corrected first signal exceeds the alarm threshold value for a predetermined time, the alarm threshold value and predetermined time being coordinated to cause no alarm signal production in response to actual concentrations of smoke that do not represent typical instances of anticipated sources of fire.

14. The fire detection system of claim 13 in which the correction circuitry offsets the first signal by no greater than a maximum drift tolerance amount and the alarm threshold value is much less than the maximum drift tolerance amount.

15. The fire detection system of claim 13 in which the ratio of the drift tolerance amount to the alarm threshold value is greater than 1.0.

16. The fire detection system of claim 13 in which the predetermined time is in the order of minutes to detect the presence of nonflaming fires.

17. The fire detection system of claim 13 in which a member criterion of the predetermined set includes a predetermined rate of change in concentration of CO₂ in the spatial region and in which production of the alarm signal occurs in response to the second signal representing the predetermined rate of change in CO₂ concentration.

18. A fire detection system that is capable of detecting flaming and nonflaming fires, comprising:

a smoke detector producing a first signal representing a smoke concentration in a spatial region;

a CO₂ detector producing a second signal representing a rate of change of a concentration of CO₂ in the spatial region; and

electrical circuitry producing an alarm signal in response to a result of a formulation to which the smoke concentration represented by the first signal and the rate of change of CO₂ concentration represented by the second signal contribute to characterize a fire condition existing in the spatial region.

19. A fire detection system of claim 18 in which the result is produced by a formulation that includes a level of smoke concentration and a rate of change of CO₂ concentration exceeding a predetermined threshold for a predetermined time.

20. The fire detection system of claim 18 in which a formulation including a combination of smoke concentration and rate of change of CO₂ concentration levels in coordination with a measurement time produces the result.

21. The fire detection system of claim 20 in which the combination and the measurement time counterbalance each other such that a larger or smaller combination value specifies, respectively, a shorter or a longer measurement time to produce the result.

22. The fire detection system of claim 18 in which the spatial region is the inside of an air duct of a structure and in which the first and second signals contributing to the characterization of a fire condition such that the smoke detector indicates the presence of fire outside the duct and the second signal indicates the presence of fire inside the duct.

23. The fire detection system of claim 18, in which the fire detection system is one of a set of nominally identical fire detection systems arranged in a network distributed in a structure, further comprising:

a central controller in data communication with the fire detection systems; and

a processor determining the location of each fire detection system for providing a map indicating the location and extent of the spread of a fire in the structure.

24. A fire detection system comprising:

a light reflection type smoke detector having a light emitter from which light propagates along a propagation path and a light sensor positioned at an angular offset relative to the propagation path, the angular offset being fixed to a relatively small angle for detecting and producing a first signal representing a smoke concentration produced by a nonflaming fire in a spatial region;

a CO₂ detector producing a second signal representing a concentration of CO₂ in the spatial region;

electrical circuitry for receiving and retransmitting the first and second signals; and

a fire alarm control panel communicatively coupled to the electrical circuitry for receiving the retransmitted first and second signals and producing an alarm signal whenever any member criterion of a predetermined set of criteria for the first and second signals is satisfied.

25. The fire detection system of claim 24 in which the smoke detector is physically separate from the CO₂ detector and in which the electrical circuitry is divided into physically separate first and second portions, the first portion receiving and transmitting the first signal and the second portion receiving and retransmitting the second signal.

26. The fire detection system of claim 24 in which the CO₂ detector includes a light source for emitting infrared light having a frequency in an absorption band of CO₂ ;

a light detector adapted to receive the infrared light emitted by the light source; and

an electrical circuit operatively associated with the light detector for computing the concentration of CO₂ and producing the second signal.

27. The fire detection system of claim 26 in which the light detector comprises a thermopile.

28. The fire detection system of claim 26 in which the light detector comprises a pyroelectric detector.

29. The fire detection system of claim 26 in which the thermopile is integrated with the electrical circuit to form a combination sensor/integrated circuit.

30. The fire detection system of claim 29 in which the smoke detector is a photoelectric smoke detector comprising a light emitting diode (LED) and a photodiode that receives light emitted by the LED to form the first signal, and in which the photodiode is integrated into the combination sensor/integrated circuit.

31. The fire sensing system of claim 24 in which the fire alarm control panel receives signals from a multiplicity of CO₂ detectors and smoke detectors installed at specific locations within a building.

32. The fire sensing system of claim 31 in which the fire alarm control panel includes circuitry for identifying the locations of the CO₂ and smoke detectors and for generating a map of smoke and fire locations within the building.

33. The fire sensing system of claim 31 in which the second signal is correlated with a member criterion corresponding to the presence of flames.

34. The fire sensing system of claim 31 in which the first signal is correlated with a member criterion corresponding to the presence of smoke.