Nitric Acid Leak at Austin Powder Plant Releases Nitrogen Oxide, Prompts Evacuations

A chemical reaction in a 5,000-gallon nitric acid process tank at Austin Powder Company’s Red Diamond facility, 32000 Powder Plant Road near McArthur and Zaleski, sent a large orange-brown plume of nitrogen-oxide gas into the air and prompted evacuation orders for Zaleski, Powder Plant Road, Morgan Road, Infirmary Road, Creek Road and surrounding areas. Company and state officials said roughly 3,000 gallons of nitric acid entered the tank and were involved in the reaction that vented nitrogen oxide to the atmosphere.

A worker discovered the leak about 8:30 a.m. on Wednesday, June 11, 2025, and the Vinton County Sheriff’s Office ordered evacuations for parts of Vinton County while the American Red Cross opened a shelter at Vinton County High School for evacuees. The Vinton County Sheriff’s Office later said, “Residents may now safely return to their homes.” The Zaleski Fire Department lifted its evacuation order around 4:40 p.m., and officials reported the release had been stopped by mid-afternoon.

Ohio Environmental Protection Agency Public Information Officer Dina Pierce described the sequence in an emailed statement: “3,000 gallons of nitric acid entered a 5,000-gallon process tank at the plant and had a reaction in the tank. The reaction within the tank created nitrogen oxide gas and was vented to the atmosphere. The air release of nitric oxide gas has since been stopped.” Austin Powder also issued a statement saying, “Immediately after discovering the NOx release, Austin Powder activated its emergency response protocols and notified the Ohio Environmental Protection Agency (EPA).”

Local responders and environmental teams conducted air monitoring around the site and reported no positive readings for nitrogen oxide so far, and modeling showed the plume remained within Vinton County. Ohio EPA said there is no current reason to believe drinking water or groundwater have been impacted, but the agency is waiting for the tank temperature to cool enough to test nearby streams for pH levels, and Austin Powder will conduct additional groundwater testing in the area. The Vinton County Health Department advised anyone experiencing coughing, shortness of breath, eye or skin irritation, headaches, dizziness or other symptoms to contact a medical professional and can be reached at (740) 596-5233.

Residents and viewers posted photos showing a large orange- to yellow-brown plume over the plant; photographer Kennedi Kovaleski provided images used with permission. The local fire department deployed drones to monitor the immediate area as first responders secured the site, and shelters at Vinton County High School accommodated displaced neighbors.

The U.S. Chemical Safety and Hazard Investigation Board announced on June 24, 2025 that it opened a formal investigation into the June 11 release and a November 24, 2024 nitric-acid-related gas release at an Austin Powder facility in Tennessee. CSB Chairperson Steve Owens said, “We are concerned that incidents involving nitric acid have occurred at two facilities owned by Austin Powder in less than seven months. While fortunately no one was injured in either incident, we want to ensure that they do not continue to happen.” The CSB said it conducted initial fact-finding at the Ohio facility before launching the formal probe, and local media reports referenced a temporary FAA flight restriction within a 30-nautical-mile radius during the incident. Austin Powder, Ohio EPA and federal investigators say testing and oversight will continue as the investigation proceeds.