An emergency oxygen system for aircraft passengers includes a hermetically welded sealed oxygen cylinder of stainless steel, a welded metal diaphragm sealing a discharge port and an extended hermetically sealed capillary tube for charging the cylinder with pressurized oxygen. A hollow piston cutter is driven to pierce the metal diaphragm as part of a first passageway delivering oxygen to the passenger. A second passageway delivers any leaking oxygen to a release port when the piston cutter is in position. A method of filling the cylinder includes welding to the cylinder a member having a metal diaphragm of a predetermined rupturable characteristic and using the open capillary tube to fill oxygen in the cylinder and subsequently crimping a portion of the capillary tube to provide a hermetic seal. A pressure gauge can be hermetically sealed to the bottom of the oxygen cylinder.