Flight Crew Air Transport Pilot (ATP)
Training / Qualification
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR
General None Reported / Taken
Procedure; Human Factors; Aircraft
While in cruise I put on my O2 mask as the Captain was leaving the flight deck. I couldn't exhale from the mask as the diaphragm appeared to be stuck. I held the mask tightly to my face and blew very hard which 'broke open' the diaphragm. I then decided to switch to emergency on the O2 panel but was unable to because there was some type of locking pin that appears non compliant; preventing its removal without a tool as it was jammed against the panel.  Had I actually need emergency oxygen; this could have become a very serious issue. This pin was obviously not the pin that is supposed to be installed.  It concerns me that it is our culture here to 'just get it done' and there was no consideration of whether or not a pilot would actually be able to select emergency O2 in an emergency. Standards should be followed in actions and the type of parts we use. I have sent a picture of the panel to [the Chief Pilot].
MD-83 First Officer discovers his oxygen mask exhale diaphragm is stuck after donning the mask in cruise. A hard blow breaks it loose but it is then discovered that the emergency oxygen switch is pinned in the off position and the pin cannot be removed.