Now, oxygen is necessary for combustion of other materials, and the higher the partial pressure of oxygen you have, the faster that reaction will progress. So a person’s clothing, if saturated in a high partial pressure of oxygen, will ignite more easily and burn hotter and faster than it would with only room air. Under sufficient O2 partial pressure, some materials will spontaneously combust, or may change from fire resistant to being readily combustible. That’s why you don’t use petroleum products on oxygen O-rings, and you shouldn’t smoke in an oxygen tent. The oxygen won’t “catch on fire” but your clothing, the tent or the bed linens may, and with great enthusiasm.