American Astronauts died during the 1967 tragedy of Apollo I. A flash fire occurred inside the command module that contained 100 percent oxygen. According to the firemen, the explosion could have been avoided if the space capsule contained air and not pure oxygen. The flames spread quickly through the cabin. The last transmission ended 17 seconds after the start of the fire. All telemetry information was lost shortly after that. Emergency responders were dispatched quickly to help. The crew most likely perished within the first 30 seconds of smoke inhalation or burns. Resuscitation efforts were futile.
The atmosphere of air that we live in is only 21 percent oxygen. What do you think might happen in atmosphere of 100 percent oxygen if something catches fire?