Abstract: The device comprises a body consisting of a top half shell and a bottom half shell, coupled to one another through the interposition of a resilient membrane which defines a pressure control chamber and a pressure reducing and metering chamber, communicating with a delivery gas outlet, the bottom half shell defining a coupling end piece with the valve of the gas pressure vessel, and a quick coupling being moreover provided, operating between the end piece and the valve, which quick coupling is adapted to operatively engage with the operating handle of a gas control valve of the adjusting device for preventing the adjusting device from improperly engaging with or disengaging from the gas pressure vessel as the gas control valve means is in its open position.