Narrative:

We left the hotel slightly early on our ride to the airport to allow extra time for inclement weather that had fallen overnight (light freezing rain; snow pellets and approximately 2 inches of snow). Upon entering the cockpit there were 2 individuals seated in the pilot seats. They identified themselves as our mechanics and that they had attempted 2 APU starts; each of which failed due to an auto-APU shutdown. As the captain and I began to get settled into the cockpit we both noticed that the rmp power switches had been turned off which we had not turned off the day before. I went outside to conduct my normal exterior preflight duties. When I returned to the cockpit the captain and I discussed the 2 APU auto-shutdowns for a short time and a call was made to maintenance control to inquire about any possible causes and/or remedies. At maintenance control's direction we 'cycled' the battery switches and the APU started normally. The maintenance personnel then informed us that the cold weather ops check had not been performed on the overnight but during my walk-around inspection I had noticed that the outflow valve was partially closed and upon returning to the cockpit I saw that the pressurization system was in the manual (man) position. The maintenance red card was on the throttle quadrant and after inquiring with the station maintenance personnel they told us that the card could be removed. I completed my cockpit preflight duties and did not note any discrepancies. Once again I cannot remember the actual O2 mask test; all I can say is that; part of my cockpit setup flow does include the test. The captain has indicated that he remembers me performing the test in during preflight. During cruise and approximately 3 hours into the flight the captain and I were making arrangements with the flight attendants to setup for a physiological break. The captain donned his O2 mask in preparation for me to leave my pilot station and then noted that the crew O2 bottle pressure had depleted to approximately 20 to 40 psi. We called the flight attendant to inform them that we would not be taking a break at this time due to a system discrepancy that we needed to sort out. After some discussion with the captain we decided to descend to FL250 and contact the company for further guidance. It was jointly decided that a diversion was the best course of action. We conducted the diversion with no issues and landed safely sometime later. Upon arrival the maintenance personnel gained access to the crew O2 bottle and determined in a very short period of time that the on/off valve on the bottle was in the off position. We completed all necessary paperwork and following a thorough ops check of the crew O2 system it was determined that it was functional and we then departed on our continuing flight without any further issues. In the future when I test the O2 masks I will perform the test for a much longer period of time to ensure that that O2 is in fact coming from the bottle and not just the residual line pressure.

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Original NASA ASRS Text

Title: An A319 crew discovered in cruise flight that the flight station O2 supply was low and so diverted where Maintenance discovered the O2 system valve had been closed and not reopened during preflight.

Narrative: We left the hotel slightly early on our ride to the airport to allow extra time for inclement weather that had fallen overnight (light freezing rain; snow pellets and approximately 2 inches of snow). Upon entering the cockpit there were 2 individuals seated in the pilot seats. They identified themselves as our Mechanics and that they had attempted 2 APU starts; each of which failed due to an auto-APU shutdown. As the Captain and I began to get settled into the cockpit we both noticed that the RMP power switches had been turned off which we had not turned off the day before. I went outside to conduct my normal exterior preflight duties. When I returned to the cockpit the Captain and I discussed the 2 APU auto-shutdowns for a short time and a call was made to Maintenance Control to inquire about any possible causes and/or remedies. At Maintenance Control's direction we 'cycled' the battery switches and the APU started normally. The Maintenance Personnel then informed us that the cold weather ops check had not been performed on the overnight but during my walk-around inspection I had noticed that the outflow valve was partially closed and upon returning to the cockpit I saw that the pressurization system was in the manual (MAN) position. The maintenance red card was on the throttle quadrant and after inquiring with the station Maintenance personnel they told us that the card could be removed. I completed my cockpit preflight duties and did not note any discrepancies. Once again I cannot remember the actual O2 mask test; all I can say is that; part of my cockpit setup flow does include the test. The Captain has indicated that he remembers me performing the test in during preflight. During cruise and approximately 3 hours into the flight the Captain and I were making arrangements with the flight attendants to setup for a physiological break. The Captain donned his O2 mask in preparation for me to leave my pilot station and then noted that the crew O2 bottle pressure had depleted to approximately 20 to 40 psi. We called the Flight Attendant to inform them that we would not be taking a break at this time due to a system discrepancy that we needed to sort out. After some discussion with the Captain we decided to descend to FL250 and contact the company for further guidance. It was jointly decided that a diversion was the best course of action. We conducted the diversion with no issues and landed safely sometime later. Upon arrival the maintenance personnel gained access to the crew O2 bottle and determined in a very short period of time that the ON/OFF valve on the bottle was in the OFF position. We completed all necessary paperwork and following a thorough ops check of the crew O2 system it was determined that it was functional and we then departed on our continuing flight without any further issues. In the future when I test the O2 masks I will perform the test for a much longer period of time to ensure that that O2 is in fact coming from the bottle and not just the residual line pressure.

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.