Narrative:

This report is not specific to a particular flight; since I did not track tail numbers/dates on this issue. Recently; within the last month or two; I have noticed multiple embraer aircraft; all that had flown 1 or more legs that day; with the crew oxygen bottle valve closed. I didn't track specific dates/tail numbers because at first; I just assumed it was a fluke or chance occurrence. However when I realized how often I seemed to find aircraft this way; I became concerned and felt that filing a report would be appropriate. Cause: all flts had one thing in common: they had spent the previous night at an outstation where overnight maintenance had occurred. The mechanics apparently turn off the oxygen for safety; but fail to turn it back on; and some of our pilots are missing the fact that they are closed on preflight. Additionally; the markings on the oxygen valve can be confusing; and you may believe you are selecting the valve's open position while actually selecting the valve's closed position. This is very troubling; because crews experiencing a rapid cabin depressurization would likely not figure out that the oxygen was off until it was too late. On my preflts I found the bottle closed; after the normal oxygen test failed to work properly. If you don't hold the test slider and button down long enough; the residual pressure in the closed oxygen system does not bleed out and you will not realize the bottle is closed.

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Original NASA ASRS Text

Title: EMB FO RPTS MULTIPLE ACFT FLOWN WITH THE OXYGEN BOTTLE VALVE CLOSED.

Narrative: THIS RPT IS NOT SPECIFIC TO A PARTICULAR FLT; SINCE I DID NOT TRACK TAIL NUMBERS/DATES ON THIS ISSUE. RECENTLY; WITHIN THE LAST MONTH OR TWO; I HAVE NOTICED MULTIPLE EMBRAER ACFT; ALL THAT HAD FLOWN 1 OR MORE LEGS THAT DAY; WITH THE CREW OXYGEN BOTTLE VALVE CLOSED. I DIDN'T TRACK SPECIFIC DATES/TAIL NUMBERS BECAUSE AT FIRST; I JUST ASSUMED IT WAS A FLUKE OR CHANCE OCCURRENCE. HOWEVER WHEN I REALIZED HOW OFTEN I SEEMED TO FIND ACFT THIS WAY; I BECAME CONCERNED AND FELT THAT FILING A RPT WOULD BE APPROPRIATE. CAUSE: ALL FLTS HAD ONE THING IN COMMON: THEY HAD SPENT THE PREVIOUS NIGHT AT AN OUTSTATION WHERE OVERNIGHT MAINT HAD OCCURRED. THE MECHS APPARENTLY TURN OFF THE OXYGEN FOR SAFETY; BUT FAIL TO TURN IT BACK ON; AND SOME OF OUR PLTS ARE MISSING THE FACT THAT THEY ARE CLOSED ON PREFLT. ADDITIONALLY; THE MARKINGS ON THE OXYGEN VALVE CAN BE CONFUSING; AND YOU MAY BELIEVE YOU ARE SELECTING THE VALVE'S OPEN POS WHILE ACTUALLY SELECTING THE VALVE'S CLOSED POS. THIS IS VERY TROUBLING; BECAUSE CREWS EXPERIENCING A RAPID CABIN DEPRESSURIZATION WOULD LIKELY NOT FIGURE OUT THAT THE OXYGEN WAS OFF UNTIL IT WAS TOO LATE. ON MY PREFLTS I FOUND THE BOTTLE CLOSED; AFTER THE NORMAL OXYGEN TEST FAILED TO WORK PROPERLY. IF YOU DON'T HOLD THE TEST SLIDER AND BUTTON DOWN LONG ENOUGH; THE RESIDUAL PRESSURE IN THE CLOSED OXYGEN SYS DOES NOT BLEED OUT AND YOU WILL NOT REALIZE THE BOTTLE IS CLOSED.

Data retrieved from NASA's ASRS site as of January 2009 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.