B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 7171
Aircraft Equipment Problem Less Severe
Aircraft; Human Factors; Incorrect / Not Installed / Unavailable Part
This was a normal operation and everything was proceeding well during the preflight. The Oxygen mask was preflighted according to section 3 of our Flight Manual the way I had been taught. Our FM states: 'Oxygen Panel: Check that mask is properly stowed and Normal/100% switch is in the 100% position.'Years ago my Instructor said that meant the doors are properly closed and the red mask handle is readily available to place the mask on your face. There was no need to open the doors. Everything checked out according to the FM specifications. Upon our crew rest break the O2 mask was removed and it was discovered that the mask did not match the same type as the Captain's mask. Upon further inspection the O2 mask was not the right type of mask for the O2 mask box that was installed. I knew this was not acceptable because of a previous O2 mask failure experience. When placed in the box the way it was; the mask appeared to be normal until it was removed.The mask appeared to work normally and the discrepancy was reported.
B737 First Officer reported that the crew oxygen mask was not the right type.