Abstract: A gas regulator/valve device particularly for use in emergency escape breathing apparatus, and comprising a T-shaped regulator piston which is movable in a stepped bore and has a nylon seat for closing a jet which receives the input (high pressure) gas. Movement of the piston by the input gas from a cylinder (not shown) is balanced by a spring. An annular groove is located in the narrow section of the bore on the remote side from the input gas pressure of an O-ring seal. As cylinder gas is used up, the piston moves upwards and eventually will expose the groove to the input gas. Thereupon, gas flows through passages and actuates a whistle or a pressure transducer. A valve assembly for gas regulators is also described. This comprises a piston member which is releasable by means of a pin to move upwards, under pressure from the regulator output, so as to expose a passage which opens into the output port. The valve is intended to be difficult to close, having once been opened.