Abstract: The faucet comprises a closure member (64) between a gas-outlet passage (60) and an intake passage (62), an outer operator connected to the closure member (64) in order to displace the latter between an open position and a closed position, and a pressure reducer (66) for controlling the pressure at which the gas flows out in the open position of the closure member (64).In order to enable the bottle to be filled, and the gas to be drawn off through the same aperture, a duct (76) is provided, branched between the intake passage (62) and the outlet passage (60), short-circuiting the pressure reducer (66) and provided with a non-return valve (70) the filling gas to flow from the outlet passage (60) to the intake passage (62) and preventing gas from flowing in the opposite direction.