Abstract: Employee #1, a janitorial maintenance supervisor at a department store, was attempting to stop water from leaking around the base of a mop basin. He sprayed four to six cans of Misty gum remover around the basin and was operating a QSP wet/dry vacuum when an explosion occurred. Employee #1 was blown back out of the room into a storage bin. He suffered second-degree burns over two-thirds of his body, especially his legs. The door was open in the room where he was working and a ventilation fan was running. The flash point of the gum remover was the same as for isobutane/propane. The vacuum cleaner was not damaged, and no other ignition sources were found in the area. The source of the ignition remained undetermined when this report was written.