Narrative:

This was a scheduled air carrier flight from dca to dfw. On the jump seat was an FAA ATC evaluator. The F/east briefed the FAA man regarding shoulder harness, seat belt, radio switches, and oxygen. I, the captain, turned around and turned on his O2 supply lever. At FL310, the F/east informed me that the crew O2 supply was indicating 200 pounds instead of the required 1200 pounds. WX on our route to lit and the blue ridge arrival into dfw was bad enough that we were given a reroute to jan and the scurry arrival. We referred to our MEL and our part one for guidance in this situation. There was no guidance for us to go by. The decision was made to descend to FL250 and to borrow the F/a's walk around O2 bottles so that we would have O2. Our MEL specifies different O2 requirements for the F/a's above and below FL250. By borrowing their bottles and descending to FL250, we increased our time of useful consciousness and had an O2 supply. We did not have a way to talk to ATC in the event of a rapid decompression since the walkaround O2 bottles do not have a microphone. We weighted the option of going to 10,000' but the fuel required to get to destination exceeded the fuel on board and we were concerned about the dfw WX also. Hence, we chose FL250. Even if we had chosen 10,000 and then had smoke in the cockpit, we would have had O2 but no way to communicate with ATC anyway. Since right.D. Is a rare occurrence, we chose FL250 and proceeded without any further incident. At dfw, I called our dispatch and asked them for guidance. He asked other dispatchers and his supervisor and they agreed that there was no guidance in the books but they felt 10,000 would have been their course of action, or divert to a base which had O2 bottles for the cockpit system. My concern is that the FAA might disagree with my decision to proceed at FL250 and find me with an error in judgement. Without written guidance, we did the best we could and we certainly don't want a fine or license action for that. Although the FAA man's emergency supply lever was found to be the cause of the O2 depletion, neither the FAA man nor the F/east could recall who pushed up the emergency lever in error.

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Original NASA ASRS Text

Title: DEPLETION OF FLT CREW OXYGEN SUPPLY IN FLT.

Narrative: THIS WAS A SCHEDULED AIR CARRIER FLT FROM DCA TO DFW. ON THE JUMP SEAT WAS AN FAA ATC EVALUATOR. THE F/E BRIEFED THE FAA MAN REGARDING SHOULDER HARNESS, SEAT BELT, RADIO SWITCHES, AND OXYGEN. I, THE CAPT, TURNED AROUND AND TURNED ON HIS O2 SUPPLY LEVER. AT FL310, THE F/E INFORMED ME THAT THE CREW O2 SUPPLY WAS INDICATING 200 LBS INSTEAD OF THE REQUIRED 1200 LBS. WX ON OUR ROUTE TO LIT AND THE BLUE RIDGE ARR INTO DFW WAS BAD ENOUGH THAT WE WERE GIVEN A REROUTE TO JAN AND THE SCURRY ARR. WE REFERRED TO OUR MEL AND OUR PART ONE FOR GUIDANCE IN THIS SITUATION. THERE WAS NO GUIDANCE FOR US TO GO BY. THE DECISION WAS MADE TO DSND TO FL250 AND TO BORROW THE F/A'S WALK AROUND O2 BOTTLES SO THAT WE WOULD HAVE O2. OUR MEL SPECIFIES DIFFERENT O2 REQUIREMENTS FOR THE F/A'S ABOVE AND BELOW FL250. BY BORROWING THEIR BOTTLES AND DESCENDING TO FL250, WE INCREASED OUR TIME OF USEFUL CONSCIOUSNESS AND HAD AN O2 SUPPLY. WE DID NOT HAVE A WAY TO TALK TO ATC IN THE EVENT OF A RAPID DECOMPRESSION SINCE THE WALKAROUND O2 BOTTLES DO NOT HAVE A MICROPHONE. WE WEIGHTED THE OPTION OF GOING TO 10,000' BUT THE FUEL REQUIRED TO GET TO DEST EXCEEDED THE FUEL ON BOARD AND WE WERE CONCERNED ABOUT THE DFW WX ALSO. HENCE, WE CHOSE FL250. EVEN IF WE HAD CHOSEN 10,000 AND THEN HAD SMOKE IN THE COCKPIT, WE WOULD HAVE HAD O2 BUT NO WAY TO COMMUNICATE WITH ATC ANYWAY. SINCE R.D. IS A RARE OCCURRENCE, WE CHOSE FL250 AND PROCEEDED WITHOUT ANY FURTHER INCIDENT. AT DFW, I CALLED OUR DISPATCH AND ASKED THEM FOR GUIDANCE. HE ASKED OTHER DISPATCHERS AND HIS SUPVR AND THEY AGREED THAT THERE WAS NO GUIDANCE IN THE BOOKS BUT THEY FELT 10,000 WOULD HAVE BEEN THEIR COURSE OF ACTION, OR DIVERT TO A BASE WHICH HAD O2 BOTTLES FOR THE COCKPIT SYSTEM. MY CONCERN IS THAT THE FAA MIGHT DISAGREE WITH MY DECISION TO PROCEED AT FL250 AND FIND ME WITH AN ERROR IN JUDGEMENT. WITHOUT WRITTEN GUIDANCE, WE DID THE BEST WE COULD AND WE CERTAINLY DON'T WANT A FINE OR LICENSE ACTION FOR THAT. ALTHOUGH THE FAA MAN'S EMER SUPPLY LEVER WAS FOUND TO BE THE CAUSE OF THE O2 DEPLETION, NEITHER THE FAA MAN NOR THE F/E COULD RECALL WHO PUSHED UP THE EMER LEVER IN ERROR.

Data retrieved from NASA's ASRS site as of August 2007 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.