Fatal hydrogen sulfide leak at US Pemex refinery under investigation

A fatal hydrogen sulfide release at a US refinery operated by the Mexican state-owned petroleum company Pemex in Deer Park, Texas, killed two workers and injured at least 35 others on 10 October.

The incident discharged almost 20 tonnes of hydrogen sulfide and nearly 14 tonnes of sulfur dioxide over several hours. Two neighbouring cities were subject to shelter-in-place orders, and a section of state highway was temporarily closed.

The US Chemical Safety and Hazard Investigation Board (CSB) is now investigating the incident. ‘This is a very serious incident that caused multiple fatalities and injuries and potentially put the surrounding community at risk,’ stated CSB chair Steve Owens.

Pemex stated that the release occurred during maintenance of the refinery’s amine regeneration unit (used to strip sulfur compounds and carbon dioxide from the amine absorbents that scrub them out of hydrocarbon streams, ready for re-use). The company claimed the initial H₂S release lasted ‘a few minutes’, and associated emissions were brought under control within about three hours.

Air quality was closely monitored for hydrogen sulfide and sulfur dioxide, and no off-site impacts were detected throughout the incident, Pemex added. Air monitoring readings at the refinery perimeter were zero for these compounds, the company said.

Legal action taken

According to Houston personal injury lawyer Ryan Zehl, who is representing local residents, there have been 14 ‘air emission’ events at the Pemex Deer Park facility since 2022. This highlights ‘a troubling pattern of disregard for safety and environmental regulations,’ he stated.

Meanwhile, three workers at the Pemex facility reportedly launched a lawsuit against the company on 14 October, seeking $1 million (£770,000) in damages for injuries sustained during the release. The family of one of the workers who died in the chemical release has also apparently sued Pemex and affiliates for his wrongful death.