Abstract: Employee #1 was loading a tray of uncapped parts containing zirconium potassium perchlorate (ZPP), a shock-sensitive explosive, into an autocapping machine. He was about to place a tray on the machine tray tracks when an explosion occurred. Metal parts were blown out from between 10 to 20 ft, and onto a tray on the lower shelf of a cart next to Employee #1. At the time of the blast, Employee #2 was working at an autoloading machine about 10 ft from the autocapping machine. Employees #1 through #4 were struck by flying parts and sustained multiple contusions and abrasions, for which they were treated and released. Before loading the autocapping machine, Employee #1 had cleaned it of any residual ZPP, as required by the company's safety procedure. He had then sent one or two trays through the machine without incident. Employee #1 was wearing the required protective aluminized suit, hood, and gloves with Kevlar lining when handling the trays. Company policy required that all employees wear a Kevlar-blend full-length smock when loading and capping parts containing ZPP. All carts, equipment, floor, shoes, and personnel were bonded to the grounding strap to dissipate any electrostatic charges. Because of the shock-sensitive nature of the explosive, sufficient residual ZPP in the tube would have caused the powder to detonate. "It was reported striding the tubes"