Nearly 24,000 pounds of methyl mercaptan escaped in the middle of the night through two valves in a poorly ventilated manufacturing building, a release stated.
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.
CSB Chairperson Vanessa Allen Sutherland said, “DuPont has long been regarded as a safety leader in the chemical industry, but this investigation has uncovered weaknesses or failures in DuPont’s safety planning and procedures. These interim recommendations lay out what the company at its La Porte facility should do to protect workers and the public.”
“Neither workers nor the public are protected by DuPont’s toxic gas detection system,” investigators stated in a release.
The building where the workers died was not equipped with an adequate toxic gas detection system to alert workers to the presence of dangerous chemicals. Also, two rooftop ventilation fans were not working, despite an “urgent” work order written nearly a month earlier. However, investigators said even working fans probably would not have prevented the lethal atmosphere inside the building due to the large amount of toxic gas released, the Safety Board release stated
La Porte plant manager James O’Connor stated: “DuPont representatives have engaged extensively with representatives of the CSB to discuss the agency’s findings and recommendations. We remain committed to cooperating with the agency throughout its investigation. DuPont is actively addressing the CSB recommendations as well as those identified from our own incident investigation.”
O’Connor added: “We value the CSB’s perspective, and we are taking their recommendations seriously. The La Porte plant is shut down and will remain so until DuPont has executed a comprehensive and integrated plan to safely resume operations.”
Separately, the company stated: “While DuPont respectfully disagrees with aspects of the report and some of the CSB’s findings, we are coordinating with the CSB as we implement the following actions:
- Improved process hazard analyses;
- Engineering analysis of the Lannate building and exhaust ventilation system, and implementing safety improvements;
- Equipment modifications and redesign, including relief systems, detectors and alarms; and
- Improved Lannate operating procedures and training for all personnel.