Fire alarm algorithm using smoke and gas sensors

• US 20050200475A1
• Filed: 02/10/2005
• Published: 09/15/2005
• Est. Priority Date: 02/11/2004
• Status: Active Grant

• Current Assignee: Southwest Sciences Inc.
• Original Assignee: Southwest Sciences Inc.
• Inventors: Chen, Shin-Juh
• Granted Patent: US 7,142,105 B2
• Time in Patent Office: Days
• US Class Current: 340/521
• 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 17/117 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 29/183 Single detectors using dual technologies G08B13/1672, G08B13/2448, G08B13/2494 take precedence
• CPC Class Codes: G08B 29/24 Self-calibration, e.g. compensating for environmental drift or ageing of components

Abstract

An apparatus for and method of detecting fires comprising detecting (with one or more detectors) levels of carbon monoxide, carbon dioxide, and smoke in an ambient environment, computing (using a processor) over time rates of increase of each of the levels, and generating an alarm if one or more of the rates of increase exceed predetermined threshold rates of increase.

Claims

1. A method of detecting fires, the method comprising the steps of:

detecting levels of carbon monoxide, carbon dioxide, and smoke in an ambient environment;

computing over time rates of increase of each of the levels; and

generating an alarm if one or more of the rates of increase exceed predetermined threshold rates of increase.

2. The method of claim 1 wherein the computing step comprises computing moving averages of one or more of the levels over a time window.

3. The method of claim 1 wherein the computing step comprises employing linear regression fitting.

4. The method of claim 1 wherein the detecting step comprises employing one or more of Fourier-transform infrared spectroscopy, non-dispersive infrared spectroscopy, electrochemical sensing, and diode laser spectroscopy.

5. The method of claim 4 wherein the detecting step comprises employing diode laser spectroscopy for detecting one or both of the levels of carbon monoxide and carbon dioxide.

6. The method of claim 4 wherein the detecting step comprises employing one or more multiple pass optical cells.

7. The method of claim 4 wherein the detecting step comprises employing one or more distributed feedback diode lasers.

8. The method of claim 4 wherein the detecting step comprises employing one or more vertical cavity surface emitting lasers.

9. The method of claim 1 wherein the detecting step detects carbon monoxide levels with a sensitivity of at least 5 ppm.

10. The method of claim 1 wherein the detecting step comprises employing for one or both of carbon monoxide and carbon dioxide levels least square fitting a measured spectrum to a model.

11. The method of claim 10 wherein the model includes a quadratic background.

12. The method of claim 1 wherein the generating step comprises generating an alarm if two or more of the rates of increase exceed predetermined threshold rates of increase.

13. The method of claim 1 wherein the generating step comprises generating an alarm if the rate of increase of smoke exceeds a predetermined threshold rate of increase and one or both of the other rates of increase exceeds the corresponding predetermined threshold rate of increase.

14. An apparatus for detecting fires, said apparatus comprising:

one or more detectors detecting levels of carbon monoxide, carbon dioxide, and smoke in an ambient environment;

a processor computing over time rates of increase of each of the levels; and

an alarm system triggered if one or more of the rates of increase exceed predetermined threshold rates of increase.

15. The apparatus of claim 14 wherein said processor computes moving averages of one or more of the levels over a time window.

16. The apparatus of claim 14 wherein said processor employs linear regression fitting.

17. The apparatus of claim 14 wherein one or more of said one or more detectors employs one or more of Fourier-transform infrared spectroscopy, non-dispersive infrared spectroscopy, electrochemical sensing, and diode laser spectroscopy.

18. The apparatus of claim 17 wherein one or more of said one or more detectors employs diode laser spectroscopy for detecting one or both of the levels of carbon monoxide and carbon dioxide.

19. The apparatus of claim 17 wherein one or more of said one or more detectors employs one or more multiple pass optical cells.

20. The apparatus of claim 17 wherein one or more of said one or more detectors employs one or more distributed feedback diode lasers.

21. The apparatus of claim 17 wherein one or more of said one or more detectors employs one or more vertical cavity surface emitting lasers.

22. The apparatus of claim 14 wherein one or more of said one or more detectors detects carbon monoxide levels with a sensitivity of at least 5 ppm.

23. The apparatus of claim 14 wherein one or more of said one or more detectors employs for one or both of carbon monoxide and carbon dioxide levels least square fitting a measured spectrum to a model.

24. The apparatus of claim 23 wherein said model includes a quadratic background.

25. The apparatus of claim 14 wherein said alarm system generates an alarm if two or more of the rates of increase exceed predetermined threshold rates of increase.

26. The apparatus of claim 14 wherein said alarm system generates an alarm if the rate of increase of smoke exceeds a predetermined threshold rate of increase and one or both of the other rates of increase exceeds the corresponding predetermined threshold rate of increase.