The U.S. Chemical Safety and Hazard Investigation Board (CSB) issued two interim safety recommendations as part of its investigation into the fatal explosion that occurred in August 2025 at the U.S. Steel Clairton Coke Works, located in Clairton, Pennsylvania, in which two workers lost their lives.

The explosion occurred in the No. 13/14 coke battery transfer area when coke oven gas leaked from process piping and ignited. Two U.S. Steel employees were killed, while four employees and one contractor were seriously injured. Additionally, six workers sustained minor injuries and were treated on-site without hospitalization. The blast also caused significant structural damage to nearby buildings.

CSB: Hazards Require Immediate Action

Although the investigation is still in its early stages, the CSB stated that it has identified potential safety risks at the Clairton Coke Works that require immediate attention for worker safety. The interim recommendations aim to prevent a recurrence of the conditions that led to the explosion and to enhance overall workplace safety.

CSB Chair Steve Owens stated:

“As our investigation into this terrible tragedy continues, we are issuing these initial recommendations to help ensure that workers at the Clairton Coke Works are not exposed to similar hazards in the future.”

Building Location and Structural Integrity Under Scrutiny

The CSB’s first recommendation calls for a comprehensive facility siting and risk assessment for all buildings currently in use or planned for future use at the Clairton facility. This assessment aims to identify potential hazards to personnel based on the proximity of buildings to process equipment.

The investigation found that two of the deceased workers and two of the five seriously injured workers were located inside or immediately adjacent to buildings near the explosion site. The CSB also determined that the buildings in the No. 13/14 battery transfer area were not adequate to protect occupants from the effects of an explosion.

The report further noted that the coke oven gas supply lines for Batteries 13 and 14, which were damaged in the explosion, were rebuilt in nearly the same location and configuration as before the incident. Although U.S. Steel stated that it relocated the control rooms for the 13/14 batteries to another building approximately 30 meters away, the CSB concluded that it is unclear whether this relocation was based on a comprehensive facility siting evaluation.

Other Batteries Also at Risk

The CSB also identified four additional coke batteries at the Clairton Coke Works where personnel are present near potentially hazardous processes. The recommended facility siting assessment is intended to determine whether similar risks exist in these areas.

The second interim recommendation focuses on addressing and mitigating identified safety risks in accordance with recognized industrial safety practices.

Lead investigator Drew Sahli commented:

“Without a comprehensive facility siting analysis, it is not possible to determine whether workers are truly protected from future fires, explosions, or toxic releases.”

The Importance of Ex-Proof Equipment and Structural Safety

The CSB’s interim recommendations once again highlight how critical it is—not only to ensure process safety—but also to consider building location, structural integrity, and the use of Ex-proof (explosion-proof) electrical equipment in industrial facilities where flammable and explosive gases are present.

In such environments, if control rooms, site offices, and electrical equipment are located too close to hazardous areas, even a minor gas leak can lead to fatal consequences. For this reason, international safety standards require the use of ATEX and IECEx-certified Ex-proof equipment in explosive atmospheres.

Türkiye Perspective: The Right Product, The Right Supply

In Türkiye, the selection and supply of appropriate Ex-proof products play a critical role in preventing similar risks in heavy industry, energy, chemical, and petrochemical facilities. In this field, Eksen Mühendislik stands out as a long-established company in the Turkish market, serving as an authorized distributor of international brands in Ex-proof electrical equipment.

Eksen Mühendislik contributes to meeting industrial safety standards by supplying ATEX-certified Ex-proof lighting, connection equipment, control boxes, and other critical field application products. Incidents like this once again demonstrate that Ex-proof equipment is not a preference, but a vital necessity.

Investigation Ongoing

The CSB stated that the investigation into the Clairton Coke Works explosion is ongoing, and that additional findings, analyses, and, if necessary, further recommendations will be shared with the public in the final investigation report.