FLC OF A DC8-63 CARGO ACFT LOST THEIR SUPPLEMENTAL OXYGEN DUE TO LINE BLOW HIGH ALT CRUISE CAUSING A REQUEST FROM ATC FLT A LOWER ALT. THE CREW WERE ABLE TO TEMPORARILY TAPE OVER THE BLOW-OUT IN THE LINE AND THEN CONTINUE ON TO THEIR DEST.

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WHILE ENRTE FROM ABC-XYZ WE HAD ONE OF THE OXYGEN LINES BLOW. THE MAIN OXYGEN BOTTLES (2: 1 CREW; 1 COURIER) HAD TO BE TURNED OFF AS SHUTTING OFF THE PAX OXYGEN REGULATORS DIDN'T STOP THE LEAK. (ALL CARGO ACFT CONFIGN; PAX SEATS IN COCKPIT ONLY.) AS THIS LEFT US WITH NO SUPPLEMENTAL OXYGEN I REQUESTED CLRNC TO DSND TO A LOWER ALT; FL210. MEANWHILE THE FE CONTINUED TO WORK ON TRYING TO FIND THE LEAK WHICH TURNED OUT TO BE A COMMON LINE FROM BOTH OXYGEN BOTTLES INTO THE OBSERVER'S OXYGEN REGULATOR. WE WERE ABLE TO CLAMP THE HOSE NEAR THE HOLE THAT OXYGEN WAS LEAKING WITH A PAIR OF PLIERS HELD BY TAPE FROM THE FIRST AID KIT. WE THEN COULD RESTORE OXYGEN TO ALL BUT ONE SEAT POS. THAT SEAT POS WAS COVERED BY BRINGING UP THE WALKAROUND OXYGEN BOTTLE FROM THE CARGO COMPARTMENT. MOST PLTS OF JET ACFT THINK OF SUPPLEMENTAL OXYGEN IN JETS FOR USE IN CASE OF LOSS OF CABIN PRESSURE; HOWEVER; IT IS ALSO USED IN CASE OF CONTAMINATED AIR (SMOKE; FIRE; HAZARDOUS SPILLS). OVERLAND; LNDG AT THE NEAREST SUITABLE ARPT WOULD BE PRUDENT AND EASY; IF THIS HAD OCCURRED OVERWATER BEING CREATIVE AND USING MATERIALS AT HAND CAN KEEP A SIT SAFE RATHER THAN DETERIORATING INTO A MORE HAZARDOUS SIT. EXAMPLE IS THAT SEEKING A LOWER ALT WOULDN'T WORK BECAUSE INCREASED FUEL CONSUMPTION. ALSO HAVING SOME BASIC TOOLS WITH YOU (IN THIS CASE A LEATHERMAN TOOL) CAN BE VERY HANDY.