Abstract: A control assembly is described for controlling the flow of gas from a gas generating unit into a gas bottle to be charged. The bottle cannot be charged until a latch has been pushed clear by means of a button and until an operating lever has been moved into an unactuated position. The button is then released to latch the bottle and the operating lever is moved to the actuated position to close a micro-switch in series with a second micro-switch which is only closed when the neck of the bottle is properly inserted. These micro-switches electrically energize an ignition unit and gas generation starts. Gas passes through a bore in a piston and a pin carried thereby and initially escapes around the outside of the gas bottle neck thus purging contaminants. The piston and pin now commence to move under the action of the gas pressure and the distal end of the pin sealingly enters the bottle. Gas pressure opens a check valve in the bottle neck and charges the bottle.