Abstract: A system for charging a metallic canister having a filler opening therein with a gas under pressure and then sealing the opening to provide a closed, pressurized canister generally consisting of means for retaining the canister in a predetermined orientation, a sealing member having a guide passageway therein displaceable between an extended position in sealing engagement with a canister disposed in the predetermined orientation, with the guide passageway therein communicating with the filler opening of the canister, and a retracted position out of sealing engagement with the canister, a first means for applying a gas under pressure to a first side of the sealing member to urge the sealing member into into its retracted position, second means for supplying a gas under pressure to an opposite side of the sealing member to urge the sealing member into its extended position in sealing engagement with the canister, third means for supplying a gas under a third pressure to the guide passageway of the sealing membe