For workers at U.S. Steel’s Clairton Coke Works outside Pittsburgh, the Aug. 11, 2025 explosion remains close enough to feel: flames, black smoke, and radio calls that a battery had exploded. Six months later, employees and community residents are still weighing what the Chemical Safety Board has found so far about how the blast happened and what it says still needs immediate attention.
The Chemical Safety Board is investigating the circumstances around the blast, which it described as occurring during preparations to replace a damaged valve detected in July and other valves. In its continuing inquiry, the agency said in December that it had identified “potentially unmitigated hazards for workers at Clairton Coke Works that warrant immediate attention,” even as it reported details of the event.
The blast killed two workers and injured 11 others, including contractors, the Chemical Safety Board said. The company said it has strengthened safety protocols in response to its own investigation, including prohibiting the use of high-pressure water for valve cleaning and reviewing its “Management of Change program,” which assesses proposed changes in procedures and evaluates risk.
In and around the plant, employees point to what they describe as lingering safety and maintenance failures at a facility where they say operators have little margin for error. “They try to say ‘safety first, safety first,’” said Brian Pavlack, a current worker at Clairton Coke Works. “Safety is not the first priority for them.”
At the same time, the Clairton plant remains a focal point for air-pollution disputes between U.S. Steel and regulators in Allegheny County. The Allegheny County Health Department said that while coking operations are allowed to emit pollution, its inspectors “inspect coking operations daily” and address violations as discovered during inspections, with a full compliance evaluation every two years. The department also said its air monitoring stations near the plant have measured a 15-25% reduction in annual average particle pollution concentrations compared with 10 years ago.
Workers and outside observers also describe a wider record of accidents and environmental conflict at the site. The story of Clairton’s risk stretches beyond the August blast: a maintenance worker was killed in a 2009 explosion, an explosion injured 14 employees and six contractors in 2010, a worker died after falling into a trench in 2014, and in February 2025 a problem at a battery led to a “buildup of combustible material” that ignited, injuring two people, according to the Allegheny County Health Department.
The August blast came as Nippon Steel took ownership of U.S. Steel. Nippon Steel acquired U.S. Steel in June 2025 in a deal valued at about $15 billion, and U.S. Steel has said it wants Clairton to keep operating. Workers and community members said they are watching closely for whether Nippon’s investment plans will translate into concrete changes at Clairton—especially given the Chemical Safety Board’s findings that hazards need immediate attention.
U.S. Steel said it does not see safety issues as systemic negligence and has stressed its safety culture. In a written statement responding to questions, the company said: “Safety is our core value and shapes our culture, influences how we lead, and anchors our responsibility to ensure that every employee returns home safely, every single day.” Nippon Steel did not respond to written questions, according to the report, and U.S. Steel stressed that it has strengthened safety protocols.
Behind the blast’s technical description is a workplace where industrial processes create explosive risk. Coke ovens at Clairton heat coal at high temperatures for hours to make coke; the process produces coke oven gas, which includes hydrogen and other gases, and can be explosive because of the hydrogen content, a former operations manager at Bethlehem Steel and steel industry consultant, Fred Rorick, said in the report. “At a coke works, when you have that, you have to be very, very, very careful,” Rorick said.
The Chemical Safety Board said the explosion happened during workers’ actions around a gas isolation valve in a basement after pumping water into the valve. The agency said U.S. Steel’s written procedure did not mention using water and that a U.S. Steel supervisor directed workers to pump the water. The report also said U.S. Steel’s vice president of the Mon Valley Works, Kurt Barshick, described a scenario during an October presentation in which workers were trapped “3,000 PSI water inside of a valve that’s rated for 50 PSI,” and he said the valve cracked and gas filled the area.
While those investigations continue, the report describes how workplace and environmental disputes have overlapped at Clairton for years. Some workers and former workers say they believe underinvestment and aging infrastructure have exacerbated both safety problems and environmental compliance concerns. “A lot of things that have happened there, where they needed something fixed and something went wrong, it was because corporate wouldn’t approve them ordering the parts,” said Jonathan Ledwich, who worked at Clairton between 2011 and 2022 trying to prevent emission leaks from the coke ovens.
Community members and regulators have also highlighted the plant’s emissions and enforcement history. Allegheny County Health Department regulators routinely clash with U.S. Steel over alleged violations of the plant’s operating permit, the report said, and it cited a history of fines and enforcement action, including a 2023 fine of more than $2 million. The county health department declined to comment on “open investigations, enforcement orders, or pending litigation,” according to the report, and said it focuses on inspections and compliance evaluations.
On the policy front, the report also described how federal rules and fee structures have shaped enforcement. It said an EPA report in 2018 asserted that emissions-based fee revenue was “diminishing as a result of emissions reductions” and could “undermine long-term program sustainability,” and that the Allegheny County Council approved raising fees in 2021 and again in November. It also said President Donald Trump temporarily exempted Clairton and other coking plants in November from provisions of a Biden-era rule that included fence line monitoring for benzene emissions.
For workers, the August blast is not just a federal investigation and an enforcement record—it is also a personal and daily weight as they return to shifts. Don Furko, a former Clairton local union president, said the blast on Aug. 11, 2025 was a “normal shift” until it became the shift he would “never forget,” and he said it has altered how he feels about returning to work. “I’ve been there 25 years. There’s been guys who have lost legs from rail equipment running over them. Bad falls and stuff like that,” Furko said. “Nothing has affected me like this has.”
Even with new ownership promising investment, the report said U.S. Steel has not publicly committed to expanding production, extending the plant’s life, upgrading safety, or reducing air-emissions at Clairton in specific terms. U.S. Steel, responding to questions about investment plans, said the company plans to invest “more than $2 billion at Mon Valley Works,” and Nippon’s promises remain a subject of scrutiny for residents and workers who have followed Clairton’s safety and pollution record for years.
In the meantime, the Chemical Safety Board said its investigation continues and that it has recommended safety-related steps, including facility siting evaluation efforts after the blast. U.S. Steel said it continues to cooperate with the Chemical Safety Board and OSHA and “evaluate their recommendations,” according to the report, as Clairton’s workers and neighbors wait for answers about both the blast itself and what will change next.