Decommissioning is a process mode: the CSB's Catalyst Refiners H₂S update

On 13 August 2026 the U.S. Chemical Safety Board released an investigation update on the 22 April 2026 hydrogen-sulfide release at Ames Goldsmith Corporation’s Catalyst Refiners facility in Institute, West Virginia. Two employees were fatally injured and four others seriously injured. The update document sets out the sequence and the issues the board is still analysing; the investigation remains ongoing.

What happened

Catalyst Refiners reclaimed silver from spent catalyst and manufactured silver oxide. At the time of the incident the facility had ceased reclamation and was being decommissioned, though the wastewater pretreatment system remained in operation. As part of decommissioning, employees were disposing of chemicals still on site through the wastewater system — for which the company had no written procedure.

Three chemicals were central. A-50, a proprietary calcium-chloride coagulant, and M-2000A, a proprietary sodium-trithiocarbonate metal precipitant, had been used to recover silver from wastewater; nitric acid was used in the reclamation process. On 22 April, workers pumped roughly 80 gallons of A-50 and 275 gallons of M-2000A into a wastewater receiving tank, then began pumping diluted nitric acid into the same tank. A chemical reaction began and a fog formed over the tank. The operator stopped the nitric-acid flow and went outside for air, then passed out and later regained consciousness. A supervisor who came to check also lost consciousness. Two more employees entered to help; one pulled the supervisor clear, but that rescuer and the other worker were both overcome by vapour and later died.

Emergency responders detected hydrogen sulfide — a colourless, highly toxic gas that is immediately dangerous to life or health at 100 ppm. A shelter-in-place order covered an area within one mile of the facility; 22 people, including four responders, were decontaminated, and 18 were taken to medical facilities.

The gaps the CSB flags

The board’s preliminary observations cluster around non-routine operations. The CSB found four full-face respirators on site, but not all were equipped with filters that would protect against hazardous gases such as hydrogen sulfide. Workers told investigators that respirator use was no longer required once the facility transitioned from production to decommissioning, and the company neither provided nor required personal gas monitors that might have warned of the H₂S. 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.”

Going forward, the CSB says it will analyse chemical hazards and incompatibilities, decommissioning hazard analysis, chemical-disposal procedures, personal protective equipment and atmospheric monitoring, and corporate governance and oversight. Full findings and any recommendations will come in the final report.

Why it matters for study teams

The recurring lesson is that decommissioning is a process mode, and often the least-studied one. A HAZOP whose nodes assume normal production rarely carries the transient operations — draining, purging, chemical disposal, mothballing — where incompatible streams get combined in vessels that were never intended to hold them. Mixing nitric acid with a trithiocarbonate solution is a foreseeable incompatibility; a chemical-compatibility review or a decommissioning-scoped PHA is precisely where that scenario should surface, along with the question of what the wastewater tank can safely receive.

Two further threads are worth noting without waiting for the final report. First, safeguards tend to erode as a plant winds down: PPE requirements and gas monitoring here were relaxed on the reasoning that production had stopped, even though hazardous chemicals and reactive combinations remained on site. Second, the casualties included would-be rescuers overcome by the same vapour — a familiar and preventable escalation that argues for atmospheric monitoring and clear entry controls around any operation that can generate toxic gas. The investigation is ongoing, and the site will follow the final report.