CSB Investigation Update: 27,000 Pounds of Toxic Gas Released at PEMEX Deer Park Refinery in October Incident

The U.S. Chemical Safety and Hazard Investigation Board (CSB) has released an update on the agency’s investigation of a fatal release of toxic hydrogen sulfide gas at the PEMEX Deer Park Refinery in Texas on October 10, 2024, which killed two workers and injured 13 others.

During a maintenance activity at 4:23 p.m., approximately 27,000 pounds of toxic hydrogen sulfide gas were released. In addition to the two fatalities and other serious injuries, the release resulted in  shelter-in-place orders issued by officials in the nearby cities of Deer Park and Pasadena, Texas, lasting for several hours, and a portion of Texas State Highway 225 was closed temporarily.

CSB Chairperson Steve Owens said, “Hydrogen sulfide is a highly toxic substance that can result in serious injury and death even at low concentrations. This dangerous incident resulted in the death of of two  workers and put others workers and the surrounding communities at very serious risk.”

The CSB’s update states that on the day of the incident two contract workers at the refinery partially opened a flanged connection on piping containing hydrogen sulfide gas, which caused the release.  One of these workers was fatally injured. The work was supposed to be done on a different, isolated piping segment located about five feet away from the flange that was opened. Two other contract workers from a separate company, who were working on equipment less than 250 feet away and downwind from the release, were also affected, with one fatally injured from the hydrogen sulfide exposure.

The CSB’s investigation into the incident is focused on several key areas, including:

• Permit-to-work practices
• Energy isolation procedures
• Contractor management systems
• Emergency preparedness, communication, and response systems
• Hazard analyses and risk assessments
• Maintenance procedures
• Training programs
• Respiratory protection
• Remote isolation capability

The CSB’s investigation is ongoing, and the CSB will provide complete findings, analyses, and recommendations in its final investigation report.

About the CSB

The CSB is an independent, non-regulatory federal agency whose mission is to drive chemical safety change through independent investigations to protect people and the environment. The agency’s board members are appointed by the President and confirmed by the Senate. CSB investigations look into all aspects of chemical incidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems. The CSB does not issue citations or fines but makes safety recommendations to companies, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. For more information, please visit www.csb.gov.