Abstract: A fire extinguisher outlet head including a sealing plug having a head part that is sheared by an explosive charge upon actuation of the extinguisher head to permit release of extinguishant, whereby the sheared head part is guided along a curved path into an position in which it is retained so as not to impede discharge of the extinguishant through a discharge passage.

Abstract: A fire protection system comprises a fire extinguisher, pneumatically operable actuator on the fire extinguisher for triggering the extinguisher, an elongate tube containing a temperature responsive gas-evolving substance, and a conduit connecting the tube to the actuator for transmitting gas pressure to the actuator. The gas-evolving substance is selected to generate, when the temperature about the tube attains a critical value within a predictable range, a quantity of gas which develops a pressure in the conduit sufficient to operate the actuator.

Abstract: A valve for sealing off pressurized fluid for an extended period comprises, a body defining a passageway, a closure member in said passageway for closing off the latter against fluid flow, a pivotally mounted arm for maintaining the closure member in its passageway closing off condition, and a catch for releasably retaining the arm in the valve closed position. In one arrangement, the closure member includes a diaphragm which extends across and divides the passageway and is arranged to burst under a sufficient pressure differential, the arm carrying a backing plate which, in its valve closed position is superimpositioned against one face of the diaphragm to prevent it from bursting.