What is the bag for on a passenger oxygen mask? We may all be familiar with the part of the cabin safety briefing where they say that, in the event of a reduction in cabin pressure, oxygen masks will drop from a compartment above our heads, yadda yadda, the bag may not inflate. What is the purpose of the bag?
Oxygen in passenger masks is either generated by oxygen generator or released from pressurized container via reduction valve. In either case it is released at fixed rate. But human breath is discontinous. So the bag acts as a buffer. You inhale the oxygen accumulated in it and then it slowly refills while you are exhaling.