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Using Multiple Sensors for Discriminating Fire Detection.


pdf icon Using Multiple Sensors for Discriminating Fire Detection. (1255 K)
Milke, J. A.

Fire Suppression and Detection Research Application Symposium. Research and Practice: Bridging the Gap. Proceedings. Fire Protection Research Foundation. February 24-26, 1999, Orlando, FL, 150-164 pp, 1999.

Sponsor:

National Oceanic and Atmospheric Administration, Washington, DC

Keywords:

fire suppression; fire detection; fire research; fire safety; fire protection; sensors; fire detectors; UL 268; carbon monoxide; carbon dioxide; room burns

Abstract:

Numerous organizations are investigating the capabilities of multi-sensor fire detectors in the pursuit of an improved fire detector. Interest in such an advance is motivated by the potential of multi-sensor fire detectors to provide faster detection with fewer unnecessary alarms. Some multi-sensor detectors have already been developed and marketed which utilize existing sensor tedhnology with an algorithm applied for the decision process. Discrimination between fire and nuisance sources can be achieved without sacrificing the time to detection by monitoring several aspects of the signature of an environment, including gas concentrations,. Increasing the number of sensors included in a detector to create an "artificial nose" can increase the sensitivity and level of discrimination. In the short term, such a detector is likely to be more expensive, have an uncertain reliability and have additional power and intelligence requirements. However, in the long term, with continued advances in sensor technology, such a multi-sensor fire detector may become feasible and practical. With the increasing interest in "smart buildings", such a detector may even become preferred, especially where a multi-sensor detector may be capable of monitoring the environment for multiple purposes, e.g. fire detection, carbon monoxide concentration, concentration of flammable gases and indoor air quality. This paper describes research to demonstrate the performance of a multi-sensor fire detector. Experimental data of the signatures from a wide variety of fires and nuisance sources represented by CO, CO2 and oxidizable gas concentrations is analyzed to develop rules for discrimination. Fire sources include flaming and non-flaming fires, while nuisance sources included aerosols and heated objects. In addition, engineering principles are applied to provide guidance on appropriate detector spacing to detect fires of a particular threshold fire size. Some discrimination between flaming fires, non-flaming fires and nuisance sources can be achieved using either a threshold concentration or rate of rise of CO2 to identify flaming fires and a rate of rise of CO for non-flaming fires. A more sophisticated approach using threshold values and rates of rise of concentrations of CO, CO2 and oxidizable gas sensors is also presented. The reduction in the time to detection and increased discrimination ability with this approach is compared to that from commercial, single-sensor smoke detectors.