Ok, in The US we are regulated by the standards of NFPA (National Fire Prevention Association) to prevent fires and explosions in our Hyperbaric chambers used for Hyperbaric Oxygen Therapy (HBOT) for people. They do explode , here is a link to a you tube video about an Equine Hyperbaric Chamber that blew up in Florida in February 2012. The last time there was an explosion of a Hyperbaric chamber with a person in it was in Japan in the 80's. As the person above has showed the triangle of fire, increase of any of those factors will make a pretty big fire. Heat , Oxygen, Fuel ... think of Apollo 1 disaster. I can't seem to find any information on the Japanese explosion on the internet but I have seen the documentation and pictures of the event when I was being trained to become an HBOT Technician. The Japan chamber explosion blew the front cap and the back cap of a Monoplace acrylic chamber. The front one blew thru a wall and killed a person in the process. The back cap blew though the wall of the building and landed in the parking lot.