Abstract: At approximately 9:30 p.m. on June 30, 1993, Employee #1, of National Service Company of Iowa, was cleaning up the cut floor at the IBP facility in Council Bluffs. IBP maintenance employees were removing a valve from the refrigerant line in the ceiling and had not locked or tagged out the main valves on the roof. The valve on the cut floor was removed and taken to the maintenance shop for alteration. The foreman gave workers their evening assignments, then went to the roof and turned on the main ventilation valves, sending ammonia through the lines and onto the cut floor. Employee #1 was overcome and died of ammonia irritation and pulmonary complications. Employees #2 through #9, who attempted to rescue Employee #1, were sent to the hospital for throat, eye, and skin irritation, treated, and released.