Abstract: A thermally-actuated cartridge (21) has a center pin (24) which is arranged to protrude through the rear of a cartridge holder (23) when the cartridge assembly (21) is not set, so that it is apparent that the cartridge assembly (21) is not set. In a fire damper for an airflow duct, the cartridge assembly (21) is used as a detent to hold a damper flap (7) open. There is a particularly convenient way of mounting the detent arrangement by having a U-shaped member (9) which carries a limb (15) acting as a backing piece for a retention quadrant (7) and a sprung bracket (16) which are squeezed together by the cartridge assembly (21). The U-shaped member (9) is mounted by a means of a limb extension (10) which slots over the damper flap axle (5) and is held by a rivet (13) in the correct orientation, the cartridge assembly (21) being screwed through a threaded bore formed by upsetting or swaging a limb (14) of the U-member (9) through a hole in the extension (10).

Abstract: A fire damper in an air duct (2) is formed by a flap (12) which in its closed position bears on a flange (6) which extends inward from the duct wall, to form a seal. The flap (12) is biased to the closed position and held open by a cable (24) which is gripped by a releasable mechanism, such as a ball clutch. The release is triggered by a fusible cartridge (34) which extends into the duct (2).