Early Detection of Room Fires Through Acoustic Emission.
Early Detection of Room Fires Through Acoustic Emission.
(431 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.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899