The U.S. Chemical Safety and Hazard Investigation Board (CSB) found that refinery operators failed to clearly label equipment and follow written procedures, leading to afatal hydrogen sulfide release in Deer Parknearly two years ago.
The board released its final report Monday about the Oct. 10, 2024, fatal incident at the PEMEX Deer Park Refinery.
Two contractors were killed, and 13 additional workers were taken to nearby hospitals to be evaluated for exposure to toxic hydrogen sulfide.
The incident started after two contract workers for Repcon, Inc. opened the wrong flange on mislabeled piping. More than 27,000 pounds of the toxic gas were released, and Deer Park and Pasadena issued shelter-in-place orders during the incident.
PEMEX and Repcon did not immediately respond to a request for comment regarding the report.
The board found that four factors contributed to the fatal toxic gas release.
The leading cause of the incident was a lack of proper identification of the piping, the board found. While the refinery provided drawings and lists of the flanges, they were not sufficient to help workers tell the difference between "nearly identical segments," according to a news release from the board.
Additionally, the tag identifying the correct flange was out of sight, the board found.
"Without reliable identification, workers searched for unlocked flange devices similar to what they had seen elsewhere in the refinery," the board said in a news release. "The CSB noted that accidental releases from opening the wrong equipment are common in the chemical and refining industries and that no industry-wide standard currently addresses this issue."
According to the report, workers also believed they were working on a unit that had been shut down during the time of the incident. They were unaware that the refinery unit was still partially operational because they had been reassigned from a unit that was not operational at the time.
The board also found that workers and management misunderstood or failed to follow written procedures, and that the work permit for the site did not address some of the dangers of working at the site.
"Two people died, and the surrounding community was put at risk because of a completely preventable mistake," the board's chairperson, Steve Owens, said in a statement. "Companies must ensure that hazards are clearly identified and that effective procedures are in place to protect workers in facilities like this and the people who live and work nearby."
Based on its findings, the board recommended that refinery operators clearly label piping and develop guidelines for identifying equipment. The board also recommended establishing a protocol to clearly inform workers of the hazards in partially operational units and implement safeguards.
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