Narrative:

Maintenance deferred all oxygen gauges as inoperative and said they would ensure oxygen was full and listed it on maintenance document. Questioned them (local maintenance, maintenance controller and maintenance controller supervisor) and all said oxygen was ok to go. Both pilot masks tested ok and I finally agreed to take aircraft because all seemed ok and I had no evidence to contrary. I have witnesses to my calling maintenance controller and what was said by several gate agents. En route to destination it was discovered by me that the oxygen no longer worked at all and we descended to 10000 ft and ZZZ1 was closest airport. Contract maintenance repaired oxygen next morning and when full bottle was installed the gauges all worked properly. Reason oxygen tested in ZZZ was there was residual in bottle but not at altitude. Maintenance then sent us maintenance document showing aircraft fixed but blaming first officer for leaving his mask in emergency as reason for depleted bottle and this is totally false. Maintenance also stated mechanic found first officer mask in emergency, however, this also untrue because I observed repair taking place and mechanic said he never touched first officer mask and will file report to that effect. Blaming pilots was just an excuse to cover up the fact that bottle was almost empty in ZZZ and obviously wasn't verified by mechanic to be full. A mask in emergency makes a very loud noise and radio calls or checklists would be impossible to perform. Mechanic in ZZZ1 also stated that all valves on oxygen were open and that only problem was empty bottle. Pilots want maintenance document containing erroneous comments removed from maintenance files as it's untrue. Error lies with maintenance and maintenance controllers in not verifying bottle pressure or other problem if it existed. Both pilots want responses as to corrective action taken to repair so we can hopefully prevent this in future. Mechanic in ZZZ1 was very good and thorough and I trusted his work or I would have refused plane. Supplemental information from acn 600211: departing, we had a maintenance deferral of the oxygen indicating system. The captain was adamant about maintenance certifying the oxygen system filled for flight, and maintenance supervisors, as well as maintenance controller were contacted concerning the deferral. We were assured that the oxygen pressure was checked at the bottle, and was sufficient for flight. The deferred oxygen gauge in the cockpit read 200 psi. We both extensively checked our oxygen equipment during preflight to be sure. When in cruise flight, the captain felt compelled to check his oxygen equipment again and was breathing on it for about 1 min and then the oxygen ran out. I tried my mask and there was nothing. We descended to 10000 ft and continued to ZZZ1 since we were between airports. We wrote up the discrepancy, went to the layover. We had the same aircraft the next day for our return flight to ZZZ. An aircraft mechanic from contract maintenance replaced the captain's oxygen mask (never reported as faulty by us) and was in the cockpit with me when we checked both masks. He replaced the oxygen bottle, and reported the old bottle had zero pressure showing on the bottle gauge. The new bottle checked out at 1745 psi on the bottle gauge. As well as the aircraft indicating system. The maintenance document we received, signed by maintenance controller, stated that captain mask found leaking, and first officer's mask selected in emergency. We departed, and upon arrival ZZZ indicated 90 psi lower, without using oxygen during the flight. Aircraft was removed from service. Oxygen indicating system operated perfectly during the flight. I have a problem with the implications of the first officer's mask being in emergency. This is impossible, and a blatant fabrication of a problem by maintenance controller. I extensively tested my mask at ZZZ before flight. The mask in emergency is so loud that it inhibits normal conversation in-flight. The captain tested his mask in-flight, breathing for about 1 min before exhaustion of the available oxygen. If my mask would've been in emergency there would've been no oxygen at all to exhaust. And finally, tech from contract maintenance stated that he never even looked at the first officer's mask, and never reported such to maintenance controller. I would like written verification that this event (first officer's mask in emergency) never occurred. In conclusion, our aircraft was dispatched illegally by maintenance, and the captain was not allowed to view the gauges or bottle by maintenance, as maintenance said 'this is a maintenance issue, not crew issue.' it was unsafe by every definition, not only for depressurization, but especially smoke and fume protection. To try to cover their poor decisions by placing blame on me (the first officer) is unconscionable. I guess that they didn't consider that the crew that was taking the aircraft out the next day brought it in, and as such would know the previous day's situation.

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Original NASA ASRS Text

Title: B737-500 CREW WAS DISPATCHED FROM A MAJOR MAINT STATION WITH A MEL'ED, DEFERRED, CREW OXYGEN COCKPIT INDICATOR SHOWING EMPTY. THE OXYGEN TANK WAS ACTUALLY EMPTY. CONTRACT MAINT TOLD THE CREW THE NEXT MORNING THE OXYGEN SYS WAS NORMAL.

Narrative: MAINT DEFERRED ALL OXYGEN GAUGES AS INOP AND SAID THEY WOULD ENSURE OXYGEN WAS FULL AND LISTED IT ON MAINT DOCUMENT. QUESTIONED THEM (LCL MAINT, MAINT CTLR AND MAINT CTLR SUPVR) AND ALL SAID OXYGEN WAS OK TO GO. BOTH PLT MASKS TESTED OK AND I FINALLY AGREED TO TAKE ACFT BECAUSE ALL SEEMED OK AND I HAD NO EVIDENCE TO CONTRARY. I HAVE WITNESSES TO MY CALLING MAINT CTLR AND WHAT WAS SAID BY SEVERAL GATE AGENTS. ENRTE TO DEST IT WAS DISCOVERED BY ME THAT THE OXYGEN NO LONGER WORKED AT ALL AND WE DSNDED TO 10000 FT AND ZZZ1 WAS CLOSEST ARPT. CONTRACT MAINT REPAIRED OXYGEN NEXT MORNING AND WHEN FULL BOTTLE WAS INSTALLED THE GAUGES ALL WORKED PROPERLY. REASON OXYGEN TESTED IN ZZZ WAS THERE WAS RESIDUAL IN BOTTLE BUT NOT AT ALT. MAINT THEN SENT US MAINT DOCUMENT SHOWING ACFT FIXED BUT BLAMING FO FOR LEAVING HIS MASK IN EMER AS REASON FOR DEPLETED BOTTLE AND THIS IS TOTALLY FALSE. MAINT ALSO STATED MECH FOUND FO MASK IN EMER, HOWEVER, THIS ALSO UNTRUE BECAUSE I OBSERVED REPAIR TAKING PLACE AND MECH SAID HE NEVER TOUCHED FO MASK AND WILL FILE RPT TO THAT EFFECT. BLAMING PLTS WAS JUST AN EXCUSE TO COVER UP THE FACT THAT BOTTLE WAS ALMOST EMPTY IN ZZZ AND OBVIOUSLY WASN'T VERIFIED BY MECH TO BE FULL. A MASK IN EMER MAKES A VERY LOUD NOISE AND RADIO CALLS OR CHKLISTS WOULD BE IMPOSSIBLE TO PERFORM. MECH IN ZZZ1 ALSO STATED THAT ALL VALVES ON OXYGEN WERE OPEN AND THAT ONLY PROB WAS EMPTY BOTTLE. PLTS WANT MAINT DOCUMENT CONTAINING ERRONEOUS COMMENTS REMOVED FROM MAINT FILES AS IT'S UNTRUE. ERROR LIES WITH MAINT AND MAINT CTLRS IN NOT VERIFYING BOTTLE PRESSURE OR OTHER PROB IF IT EXISTED. BOTH PLTS WANT RESPONSES AS TO CORRECTIVE ACTION TAKEN TO REPAIR SO WE CAN HOPEFULLY PREVENT THIS IN FUTURE. MECH IN ZZZ1 WAS VERY GOOD AND THOROUGH AND I TRUSTED HIS WORK OR I WOULD HAVE REFUSED PLANE. SUPPLEMENTAL INFO FROM ACN 600211: DEPARTING, WE HAD A MAINT DEFERRAL OF THE OXYGEN INDICATING SYS. THE CAPT WAS ADAMANT ABOUT MAINT CERTIFYING THE OXYGEN SYS FILLED FOR FLT, AND MAINT SUPVRS, AS WELL AS MAINT CTLR WERE CONTACTED CONCERNING THE DEFERRAL. WE WERE ASSURED THAT THE OXYGEN PRESSURE WAS CHKED AT THE BOTTLE, AND WAS SUFFICIENT FOR FLT. THE DEFERRED OXYGEN GAUGE IN THE COCKPIT READ 200 PSI. WE BOTH EXTENSIVELY CHKED OUR OXYGEN EQUIP DURING PREFLT TO BE SURE. WHEN IN CRUISE FLT, THE CAPT FELT COMPELLED TO CHK HIS OXYGEN EQUIP AGAIN AND WAS BREATHING ON IT FOR ABOUT 1 MIN AND THEN THE OXYGEN RAN OUT. I TRIED MY MASK AND THERE WAS NOTHING. WE DSNDED TO 10000 FT AND CONTINUED TO ZZZ1 SINCE WE WERE BTWN ARPTS. WE WROTE UP THE DISCREPANCY, WENT TO THE LAYOVER. WE HAD THE SAME ACFT THE NEXT DAY FOR OUR RETURN FLT TO ZZZ. AN ACFT MECH FROM CONTRACT MAINT REPLACED THE CAPT'S OXYGEN MASK (NEVER RPTED AS FAULTY BY US) AND WAS IN THE COCKPIT WITH ME WHEN WE CHKED BOTH MASKS. HE REPLACED THE OXYGEN BOTTLE, AND RPTED THE OLD BOTTLE HAD ZERO PRESSURE SHOWING ON THE BOTTLE GAUGE. THE NEW BOTTLE CHKED OUT AT 1745 PSI ON THE BOTTLE GAUGE. AS WELL AS THE ACFT INDICATING SYS. THE MAINT DOCUMENT WE RECEIVED, SIGNED BY MAINT CTLR, STATED THAT CAPT MASK FOUND LEAKING, AND FO'S MASK SELECTED IN EMER. WE DEPARTED, AND UPON ARR ZZZ INDICATED 90 PSI LOWER, WITHOUT USING OXYGEN DURING THE FLT. ACFT WAS REMOVED FROM SVC. OXYGEN INDICATING SYS OPERATED PERFECTLY DURING THE FLT. I HAVE A PROB WITH THE IMPLICATIONS OF THE FO'S MASK BEING IN EMER. THIS IS IMPOSSIBLE, AND A BLATANT FABRICATION OF A PROB BY MAINT CTLR. I EXTENSIVELY TESTED MY MASK AT ZZZ BEFORE FLT. THE MASK IN EMER IS SO LOUD THAT IT INHIBITS NORMAL CONVERSATION INFLT. THE CAPT TESTED HIS MASK INFLT, BREATHING FOR ABOUT 1 MIN BEFORE EXHAUSTION OF THE AVAILABLE OXYGEN. IF MY MASK WOULD'VE BEEN IN EMER THERE WOULD'VE BEEN NO OXYGEN AT ALL TO EXHAUST. AND FINALLY, TECH FROM CONTRACT MAINT STATED THAT HE NEVER EVEN LOOKED AT THE FO'S MASK, AND NEVER RPTED SUCH TO MAINT CTLR. I WOULD LIKE WRITTEN VERIFICATION THAT THIS EVENT (FO'S MASK IN EMER) NEVER OCCURRED. IN CONCLUSION, OUR ACFT WAS DISPATCHED ILLEGALLY BY MAINT, AND THE CAPT WAS NOT ALLOWED TO VIEW THE GAUGES OR BOTTLE BY MAINT, AS MAINT SAID 'THIS IS A MAINT ISSUE, NOT CREW ISSUE.' IT WAS UNSAFE BY EVERY DEFINITION, NOT ONLY FOR DEPRESSURIZATION, BUT ESPECIALLY SMOKE AND FUME PROTECTION. TO TRY TO COVER THEIR POOR DECISIONS BY PLACING BLAME ON ME (THE FO) IS UNCONSCIONABLE. I GUESS THAT THEY DIDN'T CONSIDER THAT THE CREW THAT WAS TAKING THE ACFT OUT THE NEXT DAY BROUGHT IT IN, AND AS SUCH WOULD KNOW THE PREVIOUS DAY'S SIT.

Data retrieved from NASA's ASRS site as of July 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.