Widebody; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 19063; Flight Crew Type 1171
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance
Flight Crew Overcame Equipment Problem
Procedure; Human Factors; Aircraft
Relief pilot occupying Captain's seat was attempting to don his oxygen mask. He removed it from its box and the mask detached from the supply hose. This caused a rush of crew oxygen to begin entering the hose and depletion of oxygen began. Both relief pilots were able to pinch off the supply hose and stopped the depletion of oxygen. Oxygen level fell slightly to about 1;300 pounds.All pilots returned to the flight deck and decided to continue to destination as it was the closest suitable airport at the time. Flight Attendant walk around bottle (POB) was brought into the cockpit as a backup supply as the Captain's mask was now unusable. Descent was begun shortly thereafter. In checking the aircraft's maintenance logbook it was discovered that a repair was made to the mask when it passed through the base a couple of days earlier.
An oxygen mask hose detached from its coupling resulting in leaking oxygen and rendering the crew oxygen to a low level. The crew placed a cabin walk around bottle in the flight deck as a back up.