Fire Safety Science Digital Archive

Acoustic emission (AE) 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 2.4 m cubical room constructed of gypsum board and wood. AE transducers were mounted on top of a ceiling joist and on a wall stud. The threats examined were a natural gas fire producing a thermal load up to 125 kW, and a charring condition achieved by attaching a 550 W electrical heater to a wall stud. 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 particular threats, 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 identify signals that are likely to complicate the differentiation between a false and a true fire event