OSHA fines U.S. Steel, MPW Industrial Services for Clairton Coke Works explosion

OSHA cited United States Steel Corp. and MPW Industrial Services Inc. last week after a federal investigation into the fatal Aug. 2025 explosion at a U.S. Steel in Clairton, Pennsylvania.

The incident killed two employees and injured 12 others.

OSHA concluded U.S. Steel and MPW exposed workers at the Clairton Coke Works plant to unsafe working conditions including explosion, struck-by, and high-pressure injection hazards.

Hazardous work lacked energy control for flammable gas

CSB investigators determined a 70-year-old cast-iron valve leaked gas when U.S. Steel and MPW workers performing maintenance attempted to flush it with water, causing an explosion.

Federal safety inspectors determined U.S. Steel failed to use required safety management and energy control practices for hazardous work involving flammable gas.

OSHA also concluded cleaning services contractor MPW failed to provide a relief valve for a high-pressure water system and did not coordinate energy control practices for hazardous work involving flammable gas.

Nearly $180K in proposed penalties

OSHA cited U.S. Steel with seven serious and one other-than-serious violation, proposing $118,214 in penalties.

The agency also cited MPW with four serious and two other-than-serious violations, proposing $61,473 in penalties.

Both employers have 15 business days from receipt of their citations and penalties to comply, request an informal conference with OSHA, or contest the findings before the independent Occupational Safety and Health Review Commission (OSHRC). Penalties and citations may be adjusted throughout the course of the case.