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Early Detection of Room Fires Through Acoustic Emission.


pdf icon Early Detection of Room Fires Through Acoustic Emission. (1051 K)
Grosshandler, W. L.; Braun, E.

NISTIR 5269; 17 p. October 1993.

International Association for Fire Safety Science. Fire Safety Science. Proceedings. 4th International Symposium. July 13-17, 1994, Ottawa, Ontario, Canada, Intl. Assoc. for Fire Safety Science, Boston, MA, Kashiwagi, T., Editor(s), 773-784 pp, 1993.

Available from:

National Technical Information Service
Order number: PB94-112257

Keywords:

acoustic properties; acoustic sensors; fire detection; ionization detectors; walls; ceilings; noise (sound); room fires; compartment fires; joists

Abstract:

Acoustic emission (AE) previously has been shown to be a viable concept for the early indication of an open flame impinging on various structural materials. To assess its effectiveness in a more realistic environment, experiments have been performed in a 2.5 m cubical room constructed of gypsum board and wood beams. AE transducers were mounted on top of the ceiling joists and behind the center wall panel on a vertical beam. Thermocouples were mounted at several points on the wall and ceiling, and an ionization-type smoke detector was attached to the ceiling near the door opening. Two distinct fire threats were examined: (a) a flaming fire consisting of a 0.3 m diameter pan fed with natural gas to produce a thermal load of between 12 and 125 kW; and (b) a charring condition achieved by attaching a 550 W electrical heater to a vertical wooden beam located behind the gypsum board. A signal discernable above the background was recorded from at least one AE sensor in six of nine situations. In each case, measurable acoustic emission occurred before a noticeable increase in voltage from the thermocouple mounted adjacent to the AE sensor. The conclusion is that AE emission appears to be sufficiently sensitive to detect two distinct fire situations, and that an overheated condition in a wall or ceiling can be detected if it is not more than 3 m from the transducer. Additional experiments are required to determine the type of interfering AE signals that are likely to complicate the differentiation between a false and a true fire event.