Emergency Oxygen System - Mechanism

Mechanism

There are two systems that are typically found on aircraft:

• A gaseous manifold system, which connects all oxygen masks to a central oxygen supply, usually in the cargo hold area. Pulling down on one oxygen mask starts the oxygen supply for that mask only. The entire system can usually be reset in the cockpit or in some other location in the aircraft.
• A chemical oxygen generator system connected to all masks in the compartment. Pulling down on one oxygen mask removes the firing pin of the generator igniting a mixture of sodium chlorate and iron powder, opening the oxygen supply for all the masks in the compartment. Oxygen production cannot be shut off once a mask is pulled, and oxygen production typically lasts at least 15 minutes. During the production of oxygen, the generator becomes extremely hot and should not be touched. A burning smell may be noted and cause alarm among passengers, but this smell is a normal part of the chemical reaction. This system can be found on the MD-80 aircraft, whose system is also unique in the fact that the face masks are clipped to the inside of the compartment door and do not drop out and hang, by the oxygen tube, in front of the passengers.