Abstract: Five employees of a scaffolding company were building a scaffold inside the combustion chamber of a fluidized bed boiler. The boiler had been shut down due to a tube leak. Residual ash was left in the particle return system. The employees were testing in order to locate the leak when water entered the particle return system and came in contact with the hot ash. This caused an eruption of steam and ash. Employee #1 sustained burns on 90 percent of his body and died. Employee #2 sustained second- and third-degree burns on 80 percent of his body. Employee #3 sustained second- and third-degree burns on 60 percent of his body. Employee #4 sustained burns on 30 percent of his body. Employees #2, 3 and 4 were hospitalized. Employee #5 was not hospitalized.