Archive · 12 Aug 2026
Final Report: 2025 Blast Killed 2 at Pennsylvania Steel Plant
Something very bad happened at a big factory in Pennsylvania that makes gas from coal.
An old pipe burst and blew up, and two workers died.
Eleven other people were hurt.
People who check on factory safety wanted to know why the pipe burst.
They learned that workers were cleaning the pipe with very strong water.
Nobody at the factory had written down a safe way to do that job.
Workers had been doing it the same way for at least three years, even though it was never officially a rule.
The pipe was very old and made of cast iron, which can break easily.
The safety experts said the factory must write clear rules and teach workers how to clean gas pipes safely.
They also said it was risky that workers were near the gas pipes when cleaning.
The U.S. Chemical Safety and Hazard Investigation Board issued a final report on the August 2025 explosion at U.S. Steel's Clairton Coke Works near Pittsburgh that killed two workers and injured 11, including contractors.
U.S. Steel said the blast occurred as workers flushed a gas valve with pressurized water before planned maintenance; the valve ruptured and released combustible coke oven gas.
The report found U.S. Steel had no formal procedure for the pressurized-water cleaning, which employees had performed on an ad hoc basis for at least three years before the blast.
OSHA previously fined U.S. Steel $118,214 and issued 10 citations for incomplete, outdated or inadequate procedures, practices and training.
The Chemical Safety Board recommended that U.S. Steel and an industrial cleaning contractor develop written procedures and worker training for flushing valves and cleaning piping carrying flammable or toxic gas.
- Who
- The U.S. Chemical Safety and Hazard Investigation Board, which issued the final report; U.S. Steel, owner of the Clairton Coke Works; two workers who were killed and 11 people injured in the blast.
- What
- A final federal report on the August 2025 explosion at the Clairton Coke Works, including findings on unsafe valve-flushing practices and new safety recommendations.
- When
- About a year after the blast, which occurred in August 2025.
- Where
- Clairton Coke Works, a U.S. Steel industrial facility near Pittsburgh, Pennsylvania.
- Why
- Workers were flushing a gas valve with pressurized water ahead of planned maintenance; the old cast-iron valve ruptured and released combustible coke oven gas.
Safety Board, workers and regulators
U.S. Steel
Cause and blame for the blast
Safety Board, workers and regulators
The Chemical Safety Board found employees had cleaned valve seats with pressurized water on an ad hoc basis for at least three years with no formal procedure, and member Sylvia Johnson said the blast was the result of workers routinely performing a task incorrectly over years; some current and former workers blame poor management and underinvestment.
U.S. Steel
U.S. Steel has said the explosion happened while workers were flushing a gas valve with pressurized water in preparation for routine, planned maintenance, and that the valve ruptured under intense pressure and released coke oven gas.
- Reporting agency
- U.S. Chemical Safety and Hazard Investigation Board
- Facility
- Clairton Coke Works, a U.S. Steel plant near Pittsburgh, Pennsylvania
- Blast date
- August 2025
- Fatalities
- 2 workers
- Injuries
- 11, including contractors
- OSHA fine
- $118,214 and 10 citations
- Failed valve
- More than 70-year-old cast-iron valve
- Facility status
- Largest coke works of its kind in the Western Hemisphere