Narrative:

During cruise at FL240 fuselage door warning illuminated. Appropriate emergency checklist was completed. Checklist required reduction of cabin differential pressure to zero. Cabin press warning illuminated at 16-18 thousand feet. Oxygen mask donning command was given. During donning of my mask (eros, model unknown). The inflatable harness was jammed on a piece of the mask structure. The mask could not be donned at all due to the harness position. Clearing of this jamb took aprox 30 seconds and both hands. Due to restr visibility caused by his mask, the captain was only partially aware that I was having difficulty with my mask in that I had not checked my interphone yet. Aircraft was diverted per the emergency checklist call-out of 'land as soon as possible' landed with no further difficult by or mishap. A mask failure of this type of a higher altitude could cause dire consequences. This same mask is used in aircraft with service ceilings of 400. Callback conversation with reporter revealed the following information: the reporter stated the mask stowage compartment is too small and when the mask is pulled out it comes out with the inflatable harness tangled. The reporter said one hose hooked on a projection located on the lower nose piece where it intersects with the lens. The reporter stated it took 30 seconds before oxygen was flowing. The reporter said the FAA was interested in this incident and was concerned about the projection that was hooking the hose and the remedy for change or modification.

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Original NASA ASRS Text

Title: A DEHAVILLAND 8-401 IN CRUISE AT FL240 DIVERTS DUE TO DOOR WARNING FIRST OFFICER IS UNABLE TO DON EMERGENCY OXYGEN MASK DUE TO MASK BEING JAMMED.

Narrative: DURING CRUISE AT FL240 FUSELAGE DOOR WARNING ILLUMINATED. APPROPRIATE EMER CHKLIST WAS COMPLETED. CHKLIST REQUIRED REDUCTION OF CABIN DIFFERENTIAL PRESSURE TO ZERO. CABIN PRESS WARNING ILLUMINATED AT 16-18 THOUSAND FEET. OXYGEN MASK DONNING COMMAND WAS GIVEN. DURING DONNING OF MY MASK (EROS, MODEL UNKNOWN). THE INFLATABLE HARNESS WAS JAMMED ON A PIECE OF THE MASK STRUCTURE. THE MASK COULD NOT BE DONNED AT ALL DUE TO THE HARNESS POSITION. CLRING OF THIS JAMB TOOK APROX 30 SECONDS AND BOTH HANDS. DUE TO RESTR VISIBILITY CAUSED BY HIS MASK, THE CAPT WAS ONLY PARTIALLY AWARE THAT I WAS HAVING DIFFICULTY WITH MY MASK IN THAT I HAD NOT CHKED MY INTERPHONE YET. ACFT WAS DIVERTED PER THE EMER CHKLIST CALL-OUT OF 'LAND AS SOON AS POSSIBLE' LANDED WITH NO FURTHER DIFFICULT BY OR MISHAP. A MASK FAILURE OF THIS TYPE OF A HIGHER ALTITUDE COULD CAUSE DIRE CONSEQUENCES. THIS SAME MASK IS USED IN ACFT WITH SERVICE CEILINGS OF 400. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE MASK STOWAGE COMPARTMENT IS TOO SMALL AND WHEN THE MASK IS PULLED OUT IT COMES OUT WITH THE INFLATABLE HARNESS TANGLED. THE RPTR SAID ONE HOSE HOOKED ON A PROJECTION LOCATED ON THE LOWER NOSE PIECE WHERE IT INTERSECTS WITH THE LENS. THE RPTR STATED IT TOOK 30 SECONDS BEFORE OXYGEN WAS FLOWING. THE RPTR SAID THE FAA WAS INTERESTED IN THIS INCIDENT AND WAS CONCERNED ABOUT THE PROJECTION THAT WAS HOOKING THE HOSE AND THE REMEDY FOR CHANGE OR MODIFICATION.

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.