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 gas 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 system is monitored and directed into a controller and this latter pressure is employed in determining the mass flow of gas into the receiving vessel.
