B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 152
Situational Awareness
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Human Factors
I received a call from Chief Pilot's Office concerning Aircraft X. The aircraft at some point was found with the crew oxygen valve in the 'off' position. To my knowledge and recollection; the oxygen system tested functional during normal preflight checks before operating Aircraft X for one leg [two days earlier]. My First Officer and I had a good working relationship and I don't recall any outside events or factors that interfered with our flight deck duties or cockpit preparation.While I do not believe the oxygen system valve was closed on this particular flight; I was subsequently informed that the aircraft had had its O2 bottle changed [two days prior to the event] by Maintenance. The potential for error causes me great pause and I will be extra vigilant. Seeing an O2 change in the logbook should trigger and automated closer examination of the system by every pilot. I also do not necessarily believe that Maintenance is at fault here. The valve at some point could have simply been inadvertently turned off down-line. In any case; both pilots need to make certain every system is in proper form.
The Captain and I did a normal preflight of the aircraft. I was informed that we might have flown with the O2 bottle (crew oxygen) closed. I always check that on my preflights but I am going to hold the test buttons down longer from now on.
B737 crew oxygen was discovered to be in the 'off' position subsequent to conducting a flight.