Regional Jet 900 (CRJ900)
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe
Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft
While in cruise at 34;000 feet the First Officer went to utilize his oxygen mask; so I could exit the flight deck to use the lavatory. After removing the mask from its container we discovered that the audio wire had at some point been inadvertently threaded through the headband straps. There was physically no way for us to unthread the audio wire. Subsequently this made the mask unable to be utilized. I decided to remain in the flight deck for the remainder of the flight. At the same time we unstowed the Observer oxygen mask and my First Officer held it in his lap until we descended to a safe altitude on the arrival. After landing I wrote up the mask as inoperative and had maintenance fix the problem. It is likely this event occurred somewhere during a Maintenance Inspection. There was no way for us to unthread the audio cable in flight with our knowledge of the system. Not sure how to prevent this in the future as this was likely an issue that occurred during a Maintenance function.
[Report narrative contained no additional information.]
CRJ-900 flight crew reported finding the First Officer's oxygen mask unusable during cruise flight.