Why don't the bags inflate when there is a loss of cabin pressure? Why have the bags at all?

Question

When the cabin losses pressure masks fall from above. They say that oxygen will flow to the mask even though the bag does not inflate. So.... why have the bag at all? What does it do?

Answer 1

Tanked oxygen is not stored under enough pressure for it to actually inflate anything when used; keeping oxygen under that much pressure would make the tank unstable and too risxy to store. That's true on the ground, not just in a plane--- oxygen masks used by folks in hospitals or anyone who needs extra oxygen doesn't inflate in those settings, either. So that is normal operation for an oxygen mask. The flight attendants tell you this on each flight so you know what to expect. Imagine the chaos if the masks dropped, people put them on, and they expected them to inflate like a balloon! Knowing ahead of time how the masks should look when they're working helps keep people calmer in a situation where they're probably already going to be scared.

What the bags/masks do... the air inside the plane's cabin is pressurized for a couple of reasons, one of which is the air is too "thin" to breathe at such high altitudes. This means it is poor in oxygen; if you tried to breath the air straight at that altitude, you would not take in enough oxygen, and you'd pass out. If the cabin pressure stays normal, you don't need any additional oxygen because the plane is pumping it in around you. But if that fails, you need additional oxygen added. It's just like how mountain climbers going up very tall mountains will take breathing packs with them.

Answer 2

The bag inflates when there is resistance, that is when you put it on. So it is not going to blow up like a balloon when it dropped. It is more to help recycle the air. You do not require pure oxygen anyway.