Abstract: A fluid damper in a ventilation duct serves to close the duct in the event of a fire so as to damp the flow of air in the duct. The damper comprises a retractable curtain that is normally retained in a retracted configuration by a latch mechanism attached to a frame of a fluid damper. The latch mechanism comprises a housing having at least one latch member biased so as to project from the housing and movable between a position in which it engages an end blade of the curtain so as to hold it in a retracted position and a position in which it is clear of the curtain so as to release it from the retracted position. The latch mechanism is held in the curtain retaining position by a releasable locking catch that is operatively coupled to a thermally sensitive element such that when the element reaches a pre-determined temperature it expands so as to release the locking catch and thereby allow the latch member to release the curtain.