B737-900
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe
Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft
As I was storing my oxygen mask prior to our descent; the plastic O2 supply fitting to the regulator snapped in half making the mask inoperative. We decided to replace the mask with the second observer oxygen mask vs descending due to a line of thunderstorms below us. Per the Captain's directions; I disconnected the first officer's oxygen and replaced it with the observer's mask. I checked the mask and it checked out fine. We proceeded without any further problems. We then entered the discrepancy in the log book and informed maintenance.
B737-900 FO reported his oxygen mask malfunctioned in flight and was replaced with the observer's mask.