A system and method for supplying a gas from a supply of compressed gas to a receiving vessel by measuring the pressure of gas being directed into the receiving vessel in successive selected time intervals to determine the actual ramp rate of g as being directed into the receiving vessel and providing means for comparing the actual ramp rate with a desired ramp rate and controlling the gas flow rate in response to that comparison. In a preferred embodiment the pressure of the gas at an upstream end of the syste m is monitored and directed into a controller and this latter pressure is employe d in determining the mass flow of gas into the receiving vessel.
