‘Critical deficiencies’ led to near-fatal ammonia release at Virginia food processing plant, CSB finds

THE US Chemical Safety Board (CSB) has issued its final report into a near-fatal ammonia release at a food processing plant last year, finding “critical deficiencies” in the facility’s safety systems.  

The CSB reported that around 125 kg of anhydrous ammonia were released from the packaged meal production plant operated by Cuisine Solutions in Sterling, Virginia in July 2024. Among several failings, the CSB found that the plant had no alarms or automatic shutdowns designed for ammonia releases – a common refrigerant used in the food industry.  

The toxic gas cloud rendered ten employees unconscious and led to the hospitalisation of 33 people, including one admitted to intensive care. Three other workers were admitted for serious injuries. 

Cuisine Solutions is a major supplier of packaged meals for hotels, airlines and restaurants, noted for the “sous vide” cooking method in which vacuum-packed foods are slow cooked in water baths before being cooled in chilled water. Ammonia is used as a refrigerant to regulate the temperature of the chilled water and the freezers.  

The CSB, which is set to close next month, found that the ammonia was released as a result of an unspecified process upset in a heat exchanger in the chilled water system. The CSB could not determine the cause of the upset as there were no process data available, but it was able to establish that it resulted in an overpressure in the heat exchanger surge drum which triggered an emergency pressure release. The agency has recommended an independent audit of the plant’s pressure relief system.  

The CSB also identified a “critical” factor that heightened the danger of the release: the ammonia vapour contained liquid aerosol, which made the gas cloud unusually dense and caused it to settle rapidly at ground level. Modelling showed that ammonia concentrations at ground level were “immediately dangerous to life or health”, but that “serious weaknesses” in Cuisine Solutions’ emergency action plan meant that evacuation routes took employees through the toxic cloud. The CSB has recommended that Cuisine Solutions identifies liquid or two-phase release scenarios and to implement controls to reduce their likelihood.  

The CSB recommended that Cuisine Solutions update its emergency action plan, which it found inadequate in responding to the ammonia release. It also noted that the company failed to distinguish between indoor and outdoor releases, lacked visible windsocks on site and did not account for wind speed or direction in its evacuation guidance. The report also highlighted that, while Cuisine Solutions staff had completed fire evacuation drills, they had not trained on how to respond to ammonia releases. “During the incident, many evacuees used the nearest exit as they had during drills, in some cases causing them to evacuate through the ammonia cloud,” the report noted.  

The report also recommended that Cuisine Solutions develops alternative evacuation routes and assembly points based on wind direction and that it implements emergency escape protective equipment. 

Furthermore, the refrigeration systems relied on manual shutdown – which did not happen – rather than automated controls, and that no alarms were triggered. “Instead, radio and word of mouth communicated news of the evacuation and instructions for where to exit the building,” the CSB reported. The agency has recommended Cuisine Solutions implements specific ammonia alarms and automatic shutdown for refrigeration systems.   

Steve Owens, chair of the CSB, said: “Toxic ammonia vapours can cause serious injuries and put lives at risk. 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.” 

Cuisine Solutions was approached for comment.  

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The CSB is highly respected around the world, despite having no regulatory power in the US. Since its creation in 1998, the agency has investigated more than 170 chemical incidents and made over 1,000 recommendations to help improve safety.  

CSB board member Sylvia Johnson said the investigation into the Sterling ammonia release “underscores the critical role the CSB plays in identifying safety gaps and preventing future incidents”. However, this will be its final investigation before its annual US$14 million funding is discontinued, following the Trump administration’s July decision to remove the agency from the federal budget starting in October.