An ongoing investigation by the U.S. Chemical Safety Board (CSB) of the November 15, 2014, toxic chemical leak that killed four workers at the E. I. du Pont de Nemours insecticide plant in La Porte, Texas, has uncovered flawed safety procedures, design problems and inadequate planning.
Nearly 24,000 pounds of deadly methyl mercaptan escaped in the middle of the night through two valves in a poorly ventilated manufacturing building. In one area of the plant, operations personnel attempted to clear blocked piping. Later in a different area, two workers opened valves in response to what they believed was a routine, unrelated pressure problem. The two workers were killed when liquid methyl mercaptan drained from the open valves, filling the room with toxic vapor. One of those workers made a distress call, and two additional workers died responding to that call.