Abstract: At about 10:30 a.m. on October 27, 1993, Employee #1, a chemist at a pyrotechnics and explosive ordnance facility, was preparing to screen a powder explosive material through a sieve for uniform size. He placed two spoonfuls of zirconium potassium perchlorate (ZPP) into a sieve and returned the remaining portion, about 2 pounds in a plastic container to an adjacent mixing bay. Employee #1 returned to his work station, which is designed so that the employee stands inside the building and performs the screening task on a shelf outside the building. The task and the employee are separated by a steel wall with two hand access openings. When Employee #1 reached into the right opening, the ZPP powder exploded, seriously injuring his right hand and arm.