Players breathe pure oxygen through a mask and sit in the chamber for 60 to 90 minutes.

They breathed oxygen like we do, and they must have got it from somewhere.

It's as if the challenge was how weird can we make these people and still have them breathe oxygen?

Are you saying the creatures piloting that thing don't breathe oxygen?

For this treatment, you breathe oxygen through a mask.

We can breathe pure oxygen, or a mixture of gases.

People whose lungs are compromised sometimes breathe almost 100% oxygen.

"Like a human, a tree must breathe oxygen, which it does through its roots," he said.

The pair also breathed pure oxygen for an hour while the pressure was being lowered.

"How long will we have to breathe pure oxygen?"