CSB publishes Cuisine Solutions ammonia release final report

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.

During the incident, a toxic cloud of ammonia injured dozens of workers and exposed critical deficiencies in the facility’s safety systems. 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.

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

As a result of its investigation, the CSB issued six safety recommendations to Cuisine Solutions and the International Institute of All-Natural Refrigeration (IIAR).

Following its own investigation, the Virginia Occupational Safety and Health program (VOSH) issued 10 citations through OSHA totaling $131,535.

Sous-vide cooking, food storage required refrigeration system

The Cuisine Solutions plant produces packaged food products for hotels, airlines, and restaurants, as well as other industries and consumers. The CSB’s investigation stated the facility used the sous vide cooking method: food was vacuum sealed in a specially-designed pouch and slow-cooked in a water bath.

As part of the food preparation process, the food products were immersed in chilled water after completing the cooking process. Cuisine Solutions had a refrigeration system to control chilled water temperature in its processes and also to operate freezers and food storage areas.

The plant’s food processing and storage facilities required an industrial-scale refrigeration process using ammonia as the refrigerant, which is commonly used as a refrigerant in the food industry.

Workers escaped into toxic ammonia cloud at ground level

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.

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 comprising liquid and vapor, producing a dense 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 a toxic ammonia cloud was rapidly settling at ground level, many employees passed through it as they escaped the facility.

Modeling conducted by the CSB showed that ammonia concentrations in the cloud at ground level reached levels classified by NIOSH as Immediately Dangerous to Life or Health (IDLH), putting both workers and the nearby public at serious risk.

Inadequate emergency response plans, training

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 (EAP). 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.