B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 187; Flight Crew Type 11478
Situational Awareness; Human-Machine Interface
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Human Factors
During the flight deck preparation the aircraft crew oxygen test [revealed] that the 1250 psi display would drop to 200 psi when tested. The maintenance remedy was to open the oxygen valve correctly. When the demand of a simple push to test occurred the value was not capable of supplying oxygen. A call to [Maintenance] could not determine when the last time the oxygen was serviced or for how long [this was a] problem.
B737NG Captain reported pre-flight inspection revealed the crew oxygen system bottle valve was not properly opened.