Chemical Safety Board issues interim safety recommendations after U.S. Steel explosion

The U.S. Chemical Safety and Hazard Investigation Board has issued two interim safety recommendations as part of its ongoing investigation into the August 11, 2025, fatal explosion at U.S. Steel’s Clairton Coke Works facility in Clairton, Pennsylvania.

According to the agency, the explosion occurred when coke oven gas was released from process piping in the Battery 13/14 transfer area and ignited. Two U.S. Steel employees were killed, four employees and a contractor were seriously injured, and six additional workers sustained injuries that did not require hospitalization. Nearby structures were also heavily damaged.

Although the investigation remains in its early stages, the Chemical Safety Board said it identified potentially unmitigated hazards that warrant immediate action to protect workers. The interim recommendations are intended to address those concerns while the investigation continues.

The first recommendation calls on U.S. Steel to conduct a comprehensive facility siting evaluation of all buildings at Clairton Coke Works that are currently occupied or could be occupied. Investigators determined that the two fatally injured workers and two of the seriously injured workers were inside or near buildings located in the explosion area. The agency found that occupied buildings in the Battery 13/14 transfer area were not able to protect occupants from explosion hazards.

The Chemical Safety Board noted that U.S. Steel has rebuilt damaged coke oven gas supply piping in nearly the same location and layout as before the explosion. While the company is relocating Battery 13/14 control rooms to a building about 100 feet away, investigators said it remains unclear whether the new location adequately protects workers without a formal siting analysis.

Investigators also found that Clairton Coke Works operates four additional coke batteries with personnel-occupied buildings located near potentially hazardous processes. The recommended facility siting evaluation would assess risks associated with those buildings as well.

The second interim recommendation directs U.S. Steel to address and reduce any risks identified in the facility siting evaluation using accepted industry safety principles.

The Chemical Safety Board said additional findings and any further recommendations will be included in its final investigation report once the review is complete.