Frequently Asked Questions

On August 11, 2025, around 11 a.m., coke oven batteries 13 and 14 at Clairton Coke Works exploded. Preliminary indications lead us to believe that the explosion happened when flushing a gas valve, in preparation for planned maintenance. Pressure built inside the valve, leading to valve failure and coke oven gas filling the area and ultimately exploding when finding an ignition source.

Emergency teams were immediately dispatched to the scene, where several employees were injured, and two employees sadly lost their lives.

Coke ovens heat up to over 2000°F to turn coal into coke, a substance that is nearly all carbon and crucial in steel production. Coke provides heat needed to melt iron ore and strip the ore of its oxygen, resulting in pure iron that makes strong, durable steel. Watch a brief video to learn more about the process used to transform coal into coke.

Our top priority is the safety and wellbeing of our employees and the environment. We are working closely with relevant authorities to investigate the cause of the incident and will provide additional updates as they become available. After safety checks, there is no risk at this time and the plant remains operational. Each worker continues to have a personal gas monitor in addition to fixed monitors in all locations.

Air quality monitors for Clairton, Liberty, and North Braddock currently show safe levels of PM2.5, sulfur dioxide, and hydrogen sulfide. The day of the incident, a stay-at-home order was given out of abundance of caution. U. S. Steel will continue to monitor environmental performance at all of our Mon Valley facilities, as we do around the clock.

An investigation into the incident at our Clairton Plant is being conducted by various governmental agencies including OSHA, the Chemical Safety Board, and the Allegheny County Fire Marshall, working in coordination with the United Steelworkers and U. S. Steel . Nippon Steel experts will also be on site to assist in the investigation.

The work on the previously announced hot strip mill continues, and our commitment to the Mon Valley remains strong. At this time, our primary focus remains on our employees at our Clairton Plant.