A300
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe
Flight Crew Overcame Equipment Problem
Aircraft
In cruise flight; I went to put on quick donning mask as First Officer was going to leave the flight deck for physiological needs. I pulled the mask out of the box and it came apart in my hands; it was a useless mask had there been an emergency. Where the hose attaches with the microphone to the main rubber face area was broken and dangling. The full mask section was intact but the hose/microphone area was detached and hanging by a wire; no ability to breathe oxygen from the mask. I took the disconnect oxygen point in the box and detached it and microphone wire from the Captain's box and then removed the Second Observer seat oxygen mask and installed it into the Captain's oxygen box and verified operational functionality of O2 and microphone. Maintenance entry made and mask given to the mechanic on landing.Not sure if the mask had been previously shoved in at an angle/forced into the box over many times that stressed the attach point.[Suggest] Physically pulling the mask out prior to departure would have caught this mask but still it's possible to have a good mask and in re-stowing it that it might fail that time and you may not know until the next time the mask is pulled out for use. This is the first time in the Airbus that I have seen a failed oxygen mask.
A300 Captain reported the quick donning oxygen mask 'came apart' when it was removed from the storage compartment for use in cruise flight. Mask was replaced with an observer's mask and flight continued.