Abstract: On February 10, 2012, Employee #1, an equine therapist, was treating a horse that was inside a hyperbaric oxygen therapy chamber. The horse became restless, kicked its hind leg up, and hit the rim seal of the aft access port. A spark was created, and it quickly flashed to a flame, due to the rich oxygen content. Horse hair and fatty tissue became combustibles. The fire rapidly increased the pressure inside the vessel, and the automatic high pressure relief failed to open. The pressure inside the chamber quickly exceeded the tank pressure rating, and it caused the chamber to violently rupture. Employee #1 was near the door of the chamber as it ruptured, and she was killed as a result of her injuries. Employee #2 was apparently struck by flying objects, and she sustained unspecified injuries. She was transported to the hospital and was hospitalized.