CSB Update: Fatal H2S Release at WV Refiner Tied to Missing Decommissioning Procedures
Two workers died and four others were injured after a chemical reaction released toxic hydrogen sulfide gas during decommissioning work at the Catalyst Refiners facility in Institute, West Virginia, ISHN reports, citing a new update from the U.S. Chemical Safety and Hazard Investigation Board (CSB).
What Investigators Found
The April 22, 2026 incident occurred as employees pumped roughly 80 gallons of A-50 (a calcium chloride coagulant) and 275 gallons of M-2000A (a sodium trithiocarbonate metal precipitant) into a wastewater receiving tank, then began adding diluted nitric acid from a tote. Workers noticed a chemical reaction and fog forming over the tank and stopped the nitric acid flow, but vapors had already begun affecting personnel. One employee passed out and recovered, a supervisor who responded also collapsed and recovered, but two additional workers who entered the area to help were overcome and later died.
Emergency responders detected hydrogen sulfide onsite and issued a shelter-in-place order covering a one-mile radius. Twenty-two people, including four responders, were decontaminated, and 18 were taken to local medical facilities. Hydrogen sulfide concentrations of just 100 parts per million are considered immediately dangerous to life or health.
CSB investigators found four full-face respirators onsite, but none had filters rated for hydrogen sulfide or other hazardous gases. Workers told investigators that respirator use was no longer enforced once the facility shifted from active production to decommissioning, and Catalyst Refiners never issued or required personal gas monitors. CSB Chairperson Steve Owens said the incident “underscores the need to have clear procedures and safely manage the serious chemical hazards that can arise during facility decommissioning,” adding that the agency is troubled by the absence of required respirators and gas monitors during the shutdown work.
The CSB confirmed Catalyst Refiners had no written procedure for disposing of the wastewater treatment chemicals involved. The agency’s investigation continues, with a focus on chemical incompatibilities, decommissioning hazard analysis, disposal procedures, PPE and atmospheric monitoring practices, and corporate oversight. A final report with recommendations is still pending.
What It Means for Subcontractors
- Crews performing decommissioning, demolition, or turnaround work involving legacy chemical inventories should confirm a written disposal procedure exists before transferring or combining any chemicals, especially into shared tanks or wastewater systems.
- Field teams handling wastewater treatment chemicals, coagulants, precipitants, or acids should verify personal gas monitors are issued and required on site, not just available in a supply closet, particularly once a facility moves from production to shutdown status.
- Respirator programs should not be relaxed during decommissioning phases. Subs supplying PPE or safety oversight should confirm cartridges and filters are rated for the specific gases present, including hydrogen sulfide, not just generic full-face units.
- Companies bidding decommissioning or facility closure scopes should ask clients for a documented chemical hazard and incompatibility review before mobilizing crews, since CSB is specifically examining this gap at Catalyst Refiners.
- Track the CSB’s final report on this incident, expected after the ongoing investigation concludes, for specific recommendations that could shape future OSHA or EPA guidance on decommissioning hazard analysis and PPE requirements.
