Oxygen at 21% yes. At 22%, it's like alcohol: it burns tissues and at some point it's ignitable on contact with any fat. The opposite is the risk of neutrogen,

Oxygen at 21% yes. At 22%, it's like alcohol: it burns tissues and at some point it's ignitable on contact with any fat. The opposite is the risk of neutrogen, even though it's stable and neutral, is to decrease oxygen concentration.