Abstract: On May 17, 1993, a semi-trailer load of cornstarch was being unloaded by the positive pressure system on the semi-trailer into a silo by way of a 4-inch-diameter stainless steel pipe. After one hour the silo was nearly full, so Employee #1, the silo operator, switched the manual valve to fill another silo. The manhole cover had been left off and an explosion occurred as the transfer was made using a ceiling-mounted, manual transfer switch. The explosion knocked the floor panels loose, and Employee #1 fell two stories to the main floor. He died. The explosion blew out several walls of the plant, and a fire ignited the wood roof and paper products in the warehouse. Twenty other employees escaped without injury. The half block square building of block and steel beam was destroyed.