The U.S. Chemical Safety and Hazard Investigation Board (CSB) has published a second update on its investigation into the tragic hydrogen sulfide gas release that occurred on October 10, 2024, at the PEMEX Deer Park Refinery in Deer Park, Texas. The incident claimed the lives of two contract workers and resulted in the release of over 27,000 pounds of toxic hydrogen sulfide gas. Authorities responded by issuing shelter-in-place orders for residents in Deer Park and Pasadena, lasting several hours.

CSB Chairperson Steve Owens expressed deep concern, calling the incident "a tragic event that claimed lives and endangered nearby communities." He emphasized the need for meticulous planning and execution of maintenance activities to safeguard workers and the public.

The PEMEX Deer Park Refinery, a subsidiary of Pemex (owned by the Mexican Federal Government), employs around 1,000 staff members and 1,200 contractors. As a petroleum refinery, the facility generates hydrogen sulfide as a byproduct, posing significant health risks if released.

On the day of the incident, maintenance contractors were removing piping isolation devices known as blinds from one of the refinery's Amine Regeneration Units (ARUs), specifically ARU6. However, during this process, workers mistakenly opened a flange on a pressurized piping segment linked to ARU7, another unit still containing hydrogen sulfide gas. At approximately 4:23 p.m., this error caused a significant release of the toxic gas.

One contractor working on the task died at the scene from exposure to the lethal gas. Additionally, wind carried the hydrogen sulfide to another unit where other contractors were working. Tragically, one of these downwind workers was also fatally injured.

The CSB continues its investigation, with key areas of focus including:

• Safe work practices
• Maintenance policies and procedures
• Emergency preparedness

The CSB’s final report will provide detailed findings, analysis, and recommendations aimed at enhancing safety protocols to prevent similar incidents in the future.

The CSB is an independent federal agency tasked with investigating incidents involving hazardous substances. Its mission is to conduct investigations, issue recommendations, and promote improved safety practices across industries. Although the CSB does not impose fines or citations, it advises organizations such as OSHA, EPA, industry groups, and labor unions on enhanced safety measures. The agency’s board members are presidential appointees confirmed by the Senate.

The CSB’s continued efforts aim to improve industry safety standards and protect both workers and surrounding communities from hazardous incidents.