U.S. Chemical Safety Board Releases Final Report on July 2024 Hazardous Ammonia Release at Cuisine Solutions Facility in Sterling, Virginia

Washington, D.C. - September 25, 2025 - The U.S. Chemical Safety and Hazard Investigation Board (CSB) today released its final report on the July 31, 2024, release of hazardous anhydrous ammonia at the Cuisine Solutions, Inc. food processing facility in Sterling, Virginia. The incident led to a toxic cloud of ammonia that injured dozens of workers and exposed critical deficiencies in the facility's safety systems.

The Cuisine Solutions plant produces packaged food products for hotels, airlines, and restaurants, as well as other industries and consumers. The plant's food processing and storage facilities require an industrial-scale refrigeration process, which uses ammonia as the refrigerant. At approximately 8:20 p.m. on the day of the incident, a malfunction in the ammonia refrigeration system caused an overpressure event in a vessel known as the Heat Exchanger 5 Surge Drum. The CSB found that a process upset in a heat exchanger led to overpressure in the surge drum, triggering the release.

"This investigation underscores the critical role the CSB plays in identifying safety gaps and preventing future incidents," said CSB Board Member Sylvia Johnson. "By thoroughly examining the causes of chemical incidents and issuing clear, actionable recommendations, the CSB helps protect workers, communities, and the environment."

In response to the overpressure, an emergency pressure relief valve activated and discharged approximately 275 pounds of anhydrous ammonia-a highly toxic substance-directly into the atmosphere. The release occurred in a "two-phase" flow (liquid and vapor), producing a dense toxic ammonia cloud that rapidly settled at ground level.

The emergency valve discharged ammonia near where employees were gathering as they evacuated the plant during the ammonia release. As a result, because the toxic ammonia cloud was rapidly settling at ground level, many employees were passing through the toxic cloud as they escaped the facility. Modeling conducted by the CSB showed that ammonia concentrations in the cloud at ground level reached levels classified as "Immediately Dangerous to Life or Health (IDLH)", putting both workers and the nearby public at serious risk.

At the time of the release, 286 employees and contractors were onsite. When emergency responders arrived, they found more than ten individuals unconscious. In total, 33 people were transported to area hospitals. Four were admitted for serious injuries, including one to intensive care.

During the release, the facility's ammonia detection system did not trigger any alarms, no evacuation signal was sounded, and no one at the facility initiated an emergency shutdown of the equipment that was causing the ammonia release. The lack of an organized emergency response allowed the situation to escalate and caused more workers to be exposed before reaching safety.

In addition to mechanical failures, the CSB identified serious weaknesses in the facility's Emergency Action Plan. The plan did not distinguish between indoor and outdoor releases, lacked procedures based on wind direction, and offered no guidance for shelter-in-place decisions. Employees were not adequately trained on emergency protocols, and drills were found to be ineffective. The resulting confusion delayed evacuation and increased the number of exposures.

Property damage from the incident was estimated at $3 million, including production losses with parts of the plant remaining offline for up to 38 days.

"Toxic ammonia vapors can cause serious injuries and put lives at risk," said CSB Chairperson Steve Owens. "Companies must ensure that toxic ammonia releases are discharged safely and that they have proper procedures in place to respond appropriately when a release occurs."

As a result of its investigation, the CSB issued several safety recommendations to Cuisine Solutions, including significant improvements to the facility's Emergency Action Plan. The CSB also issued recommendations to the International Institute of All-Natural Refrigeration calling for stronger industry guidance on preventing or mitigating two-phase ammonia releases, to help prevent similar incidents in the future.

The CSB is an independent, nonregulatory federal agency charged with investigating incidents and hazards involving the catastrophic release of extremely hazardous substances. Its core mission includes conducting incident investigations, formulating safety recommendations, advocating their implementation, issuing reports on findings, and conducting chemical hazard studies.

Board members are appointed by the president and confirmed by the Senate. The CSB does not issue citations or fines but makes safety recommendations to companies, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA.

For more information, please visit www.csb.gov. Contact Communications Manager Hillary Cohen at [email protected].