Narrative:

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.

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Original NASA ASRS Text

Title: B737 crew oxygen was discovered to be in the 'off' position subsequent to conducting a flight.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.