On November 15, the U.S. Chemical Safety and Hazard Investigation Board (CSB) released an update on its investigation into a July 31 hazardous ammonia release at the Cuisine Solutions, Inc., food processing facility in Sterling, Virginia.

On July 31, anhydrous ammonia was accidentally released at Cuisine Solutions’ facility. At the time of the incident, 286 personnel were on-site, including employees and contractors.

According to the CSB, an emergency pressure relief valve discharged ammonia horizontally near the roof of the building, and the released ammonia formed a toxic cloud. Some personnel were exposed to ammonia vapor as they evacuated the facility.

Cuisine Solutions reported approximately 170 pounds of anhydrous ammonia was released.

“Anhydrous ammonia is a toxic substance, and exposure to even small amounts can have significant adverse health impacts,” CSB Chairperson Steve Owens said in an agency statement.

“The formation of a toxic ammonia cloud like the one in this incident can pose serious potential risks not just to those in the immediate vicinity, but to the surrounding community as well.”

Cuisine Solutions, a privately held corporation, began operations at the Sterling plant facility in 2013, according to the CSB. The company produces cooked, packaged food products for hotels, airlines, restaurants, and other industries, as well as for consumers, using sous vide cooking methods.

Cuisine Solutions’ refrigeration system uses anhydrous ammonia as a refrigerant to control chilled water temperature in its processes and operate freezers and food storage areas. Anhydrous ammonia is commonly used in the food industry.

CSB investigators learned some personnel unwittingly exited the building near or into the ammonia cloud during the evacuation and were exposed to ammonia vapor. While part of the ammonia vapor cloud wasn’t visible, the concentration of ammonia was high enough to harm some evacuees, including outside the visible cloud.

Forty workers were evaluated at local medical facilities, and four were admitted to local hospitals—one was admitted to an intensive care unit.

CSB investigators continue to gather facts about the incident. Key questions and topics still under investigation include the following:

• Potential causes of the opening of the ammonia emergency pressure relief valve,
• The total quantity of ammonia released,
• Cuisine Solutions’ emergency action plan for an ammonia release,
• Cuisine Solutions’ process safety management (PSM) and risk management programs and policies, and
• Codes and standards for ammonia refrigeration systems.

Complete findings, analyses, and any recommendations will be detailed when the CSB issues a final investigation report.

The CSB is a nonenforcement agency that investigates chemical incidents to determine a cause or probable cause. It issues no citations or penalties but examines incidents and hazards resulting from the production, processing, and handling of chemical substances that can result in death, serious injury, or environmental or property damage.

In its investigation reports, the CSB issues recommendations for companies, industry groups, standards-setting organizations, and other federal agencies, including the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA). The board has 12 open recommendations for OSHA.