The disclosed coupling can include an elongate body having an opening at each end, the openings linked by a conduit； a valve assembly located within the elongate body. The valve assembly is movable between an open position, in which gas can pass between the openings along the conduit, and a closed position in which gas flow between the openings is prevented； a biasing assembly arranged within the elongate body to move the valve assembly into the closed position； and a heat activatable stop located in the region of each opening, operable to hold the valve assembly in the open position against the biasing assembly, and adapted to release the valve assembly to allow the biasing assembly to move the valve assembly to the closed position at an activation temperature.
