Abstract: Apparatus and method for detecting a gas leak in a gas distribution system or part thereof, and comprising: (a) a gas inlet connected to a gas-consuming peripheral (10); (b) a means (50) of detecting gas flow rate, which is situated downstream of and close to said inlet; (c) a variable-volume buffer chamber (11), coupled to said distribution system downstream of the detection means (50); (d) a valve (6) controlled by a control means (6A) for leaving or not leaving the gas free to pass from the gas source or supply to the buffer chamber (11) according to the amount of gas present therein; and (e) a means (8) capable of emitting a leak signal when the detection means (50) detects a gas flow rate higher than a predetermined value when the control means (6A) is interrupting the supply of gas to the buffer chamber (11).