What was found
AT FLIGHT LEVEL 350, NOTICED CREW 02 BOTTLE WAS LOSING PRESSURE. DESCENDED TO LOWER ALTITUDE (170). REMAINDER OF FLIGHT, PRESSURE REMAINED AT 1000 PSI. SERVICED CREW 02 BOTTLE TO 1800 (WAS 1000) PSI. FOUND LINE FROM BOTTLE TO VALVE FITTING ON BULKHEAD LEAKING. REMOVED LINE, CLEANED FITTING. REINSTALLED LINE, NO LEAK NOTED. LEAK CHECKED SYS AT BACK OF ALL 3 02 REGULATORS. REMOVED SIDE PANEL ON F/O'S LOWER SIDEWALL & LEAK CHECKED FITTING BELTING PANEL. REINSTALLED PANEL & ALL 3 REGULATORS, LEAK CHECKED. ALL LINES LEAK CHECKED GOOD. ALL 3 MASKS AND REGULATRORS GOOD. PRESSURE HELD STEADY FOR 2.5 HRS AFTER MASK CHECKS & FIXING LEAK IN LINE 02 PRESSURE WAS 1750 PSI AT 16:15 GMT 10-08-05.