Plant Blast in Plaquemine, LA, 'Should Have Never Happened,' Feds Rule

AVID J. MITCHELL

The Advocate, Baton Rouge, La.

(TNS)

A large explosion at Dow’s complex in Plaquemine in mid-2023 was a “catastrophic incident” that “should have never happened,” set in motion by workers accidentally leaving a light inside a large chemical drum following repairs, a federal safety agency says.

The independent agency, the U.S. Chemical Safety and Hazard Investigation Board, recommended Dow Chemical Co. and two national fire safety organizations adopt procedures and rules to prevent similar kinds of accidents from happening again.

The panel doesn’t have regulatory authority but investigates serious chemical accidents and suggests way to avoid them in the future.

The explosion in Dow’s Glycol II unit on July 14, 2023, in Iberville Parish released nearly a decade’s worth of typical emissions of the flammable and potent carcinogen ethylene oxide – more than 31,000 pounds — along with 16 other chemicals in 12 hours. The release created a towering fire that took a day and a half to bring under control and weeks afterward to cleanup.

Hundreds of nearby residents had to shelter in place for hours and stay inside with their air-conditioners off during a steamy summer night, while officials closed nearby highways.

The fire has triggered scrutiny from regulators, including $31,250 in fines to settle safety violations from the U.S. Occupational Safety and Health Administration in October 2024 and a U.S Environmental Protection Agency inspection that identified a series of safety, training and plant design issues.

In a new report on the fire, the Chemical Safety Board identified a cause — the work light — that other agencies and Dow had reported previously.

But the chemical board laid out the series of breakdowns that led to the fire in far greater detail, including that the design of some of Dow’s process equipment and its procedures to ensure pipelines are clear of hazardous chemicals contributed to the “severity of the incident.”

'Enormous consequences'

The light had been left in what’s known as a reflux drum after turnaround maintenance in May 2023. When the Glycol II Unit was restarted and filled with ethylene oxide, the light broke down and debris eventually flowed into downstream equipment, breaking open a protective disc, the safety board said.

The broken disc allowed ethylene oxide to enter downstream pressure relief piping containing oxygen, allowing the chemical to ignite. Then, the flame moved farther through more equipment into the reflux drum, which exploded, CSB investigators found.

“This catastrophic incident should never have happened,” Steve Owens, board chairperson, said in a statement. “The workers did not remove all the work lights from inside the drum, and Dow did not have an effective procedure in place to ensure that they did so. When dealing with a highly hazardous chemical like ethylene oxide, even a seemingly small mistake can have enormous consequences.”

Dow officials said they recognize the board’s role in reviewing chemical incidents and its “goal in preventing a recurrence,” but that they were already at work learning from what happened.

“The agency’s recommendations are consistent with the recommendations that came out of Dow’s internal root cause investigation,” company officials said in a statement. “Dow remains dedicated to learning from this event and preventing incidents such as this from happening again.”

The safety board noted that Dow adopted a new vessel closure process among other measures, so it did not need to make those recommendations. However, the safety board said it was “urging Dow to ensure that the company strictly adheres to the new requirements.”

It did recommend that Dow improve procedures to make sure closed pipelines remained “inert,” meaning dangerous chemicals aren’t left in a line that is supposed to be shut, and that the inert lines are monitored continuously.

'Clean and verified'

The safety board identified deficiencies in the system that filled closed lines with nitrogen and made them inert. The company “was unaware that nitrogen had slowly leaked out” of a relief pipe that then filled with outside air, including oxygen.

That relief pipe was one of the pieces of equipment that received flammable ethylene oxide once debris from the left-behind light had damaged other equipment.

“Companies must ensure that equipment is clean and verified before startup, that inerting systems are actively monitored, and that pressure relief systems are designed to prevent flame propagation," added Mark Wingard, a safety board supervisory investigator.

The safety board also spotted flaws in the design of Dow’s emergency pressure relief system because it routed back to the reflux drum. Flames in the equipment were able to reach the drum because of this structure and “intensify the explosion,” the safety board said.

The board noted that Dow could have reworked this flawed design in 2010 when the company replaced equipment.

OSHA originally proposed fining Dow $46,875 over three serious safety violations stemming from the fire, including a lack of procedures to prevent left-behind equipment, but agreed to reduce the number to two and the severity of one of them after Dow appealed.

EPA’s inspection noted problems with the safety of worker emergency shelter buildings and emergency relief valves, among several other problems. Dow was issued a notice of noncompliance in January 2025 but has not been fined.

The safety board advised the National Fire Protection Association and the American Society of Safety Professionals to update their startup safety rules following the post-repair cleanup of tanks and other enclosed vessels.

© 2026 The Advocate, Baton Rouge, La.. Visit www.theadvocate.com. Distributed by Tribune Content Agency, LLC.