B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 184
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Procedure; Human Factors
Chief Pilot on Call notified me at home that Aircraft X was found to have oxygen shut off valve only 1/4 open.  We flew the Aircraft X [earlier] and did not catch this 200 psi drop via the oxygen pressure drop test.
After the aircraft arrived; I performed my exterior pre-flight inspection in accordance with B737 AOM section 6.2. No abnormalities were found with oxygen pressure relief disc. When I returned to the cockpit; I completed the first preflight procedure in accordance with B737 AOM section 6.3. The Crew oxygen system was preflighted in accordance with B737 AOM section 16.1.1. During the test there was no noticeable drop in Crew oxygen pressure. I noticed no defect in the Crew oxygen system.
B737 flight crew reported they were notified after a flight that the aircraft crew oxygen bottle valve was not fully open.