The gas pressure regulator has a housing within which a diaphragm (1) is provided that responds to the gas pressure on one side and spring pressure on the other to provide the regulating action. An adjuster ring (5) is set into the cylindrical stem of the valve. The ring loads the spring (4) to give the reference pressure. The ring is made of a metal that melts at a safe temperature and so releases the spring and causes the valve to close.
