overpressure and the membrane is arranged to form a part of the chamber 39 s wall application_number US 25035703 A description 0028 fig1 shows a first embodiment of a gas dispensing device 2 according to the invention the gas dispensing device 2 has a closed chamber 4 holding a gas at a predefined overpressure to be dispensed a membrane 6 is arranged at one end of the chamber 4 the membrane 6 can occupy a smaller or larger part of the chamber 4 gas inside the chamber 4 diffuses out into atmosphere when the membrane 6 is uncovered when the gas dispensing device 2 is placed in the flow paths of a breathing apparatus the gas can be dispensed into a breathing gas a covering means covers the membrane 6 before the membrane is put into use this prevents leakage of gas before dispensing is to take place 0029 fig1 shows how the covering means can be formed by different segments 8 a c removed one at a time one segment has already been removed to show the membrane from the chamber 4 the magnitude of the dispensed dose can be selected by exposing the membrane to differing degrees for.