Abstract: Disclosed is a device for regulating the pressure and/or flow of a gas stream, which device comprises a housing (9, 109) which is provided with a pressure-regulating chamber (4, 104), at least part of whose wall comprises a diaphragm (10, 110), which diaphragm (10, 110) is subjected, on the side remote from the pressure-regulating chamber (4, 104), to an adjustable prestressing force, the pressure-regulating chamber comprising an inlet opening (3, 28, 128) for a gas and an outlet opening (5, 29, 129) for a gas, it being possible for at least one of the openings (3/5, 28/29, 128/129) to be completely or partially closed off with the aid of a displaceable closure member (15, 115) which is connected to the diaphragm (10, 110) in such a manner that the position of the closure member is dependent on the displacement of the diaphragm.