Abstract: Two employees were seriously burned in a flash fire that occurred while they were spray painting in a booth at a maintenance facility. There was an explosion, and the facility caught on fire. The employees were able to escape, but the building and the booth was destroyed. The fire department investigation determined that the fire was caused by the ignition of flammable vapors by an undetermined ignition source. Later, it was discovered that there was a gas-fired heater in the booth and the associated electrical wiring, including the thermostat, did not comply with requirements for a Class 1, Division 1, hazardous location. Employee interviews indicated that the heater had been in use, and one employee believed he heard the unit heater come on just before the explosion. The employees were treated at a hospital for first- and second-degree burns.