An employee was using a vacuum trailer to clean up a crude oil spill and contaminated soil from the tank of a trailer. A valve on the back door of the trailer had frozen overnight, so the employee was using a handheld propane torch to thaw the valve when heat from the torch ignited vapors in the tank. This blew the back door open. It struck the employee in the lower abdomen, causing a 10-inch-long laceration and chest burns.