Abstract: On October 10, 2010, Employee #1 was rinsing the interior of a pressure vessel with water as he stood on an exterior scaffold. While cleaning the vessel, flammable vapor from an undetermined source within the vessel ignited and caused a flash fire. He suffered severe upper body burns from the flash fire. The source of the flammable vapor was undetermined; however, residual pyrophoric catalyst could have been a potential ignition source. The vessel had been vented to atmosphere for greater than two hours, and gas testing may have been lacking when Employee #1 was cleaning the vessel. Additionally, he was wearing flame resistant clothing, even though he sustained severe burns. Emergency medical personnel were summoned. They arrived and transported him to a medical center. At the medical center, he received treatment, but died approximately a month later.