Ignored warnings preceded toxic gas release at McArthur plant, article says

Alarm warnings were already sounding at Austin Powder’s Red Diamond Plant near McArthur when the worst happened: nearly two tons of nitrogen oxide gas escaped from a 5,000-gallon nitric acid tank on June 11, 2025, after warnings had been repeated and then silenced. The release at 430 Powder Plant Road quickly became a public-safety emergency for Vinton County, forcing part of the county to evacuate and putting nearby families, plant workers and first responders in the middle of a toxic plume they could not immediately see or measure.

The Ohio Environmental Protection Agency said it was notified at 9:44 a.m. that day that an unknown contaminant had entered the tank, triggering a chemical reaction that produced nitrogen oxide gas. The agency said the release was stopped, no injuries were reported and the plume dissipated later that day. The evacuation order for nearby Zaleski was lifted on June 11, but the episode left open a more troubling question for Vinton County residents: why did the warnings continue for weeks before the release reached a point that forced an evacuation?

State and local agencies rushed in as the event unfolded. Ohio EMA, the Ohio Department of Public Safety, the Ohio Department of Health, the Vinton County Health Department, the Vinton County Sheriff’s Office and local fire departments all took part in the response. Ohio EPA said local firefighters used drones to monitor the immediate area, while air monitoring had not shown positive readings for nitrogen oxide. Even with the all-clear on the day of the incident, the county was left to absorb the uncertainty of what had been in the air and how far it could have spread.

The U.S. Chemical Safety and Hazard Investigation Board later opened an initial investigation into the June 11 release and described it as an accidental release of nitrogen oxides and nitric acid from an acid storage tank at about 8:15 a.m. local time. By December, the board said its investigations into Austin Powder incidents in Ohio and Tennessee were still ongoing. That lingering review matters in McArthur, where the Red Diamond facility has operated since 1930, spans about 1,200 acres and serves as Austin Powder’s core manufacturing plant in North America, producing nearly the company’s entire product line except detonators.

OSHA later cited Austin Powder for process-safety failures tied to the incident, including not compiling and maintaining process safety information for excess nitric acid storage tank TA-520, failing to develop and implement a temporary operations phase operating procedure and failing to implement a management-of-change procedure when the normal shutdown procedure was not followed. Austin Powder later said the plant resumed normal operations after the controlled venting and full assessment, and said it would reimburse evacuation-related expenses for affected residents. For Vinton County, the central issue remains whether the warning systems, oversight and emergency safeguards around one of the county’s largest industrial sites were enough to protect the people living closest to it.