Safety board fills in details of deadly DuPont leak

The US Chemical Safety Board (CSB) has completed a seven-month interim investigation into the events and safety failings leading to a methyl mercaptan release that killed four workers at a DuPont plant in La Porte, US.

The incident happened after workers were trying to clear a blockage caused by a solid mercaptan hydrate in pipework taking liquid methyl mercaptan into the manufacturing unit. When the blockage was cleared, the toxic material ended up diverted into the vent piping, which was not equipped with appropriate gas sensors.

‘Neither workers nor the public are protected by DuPont’s toxic gas detection system,’ CSB investigators said.  ‘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, the investigators pointed out that even working fans probably would not have prevented a lethal atmosphere inside the building, owing to the large amount of toxic gas released.

The CSB has made detailed recommendations of what DuPont should do to prevent future incidents, some of which relate directly to the buildings involved, while others are more general.