On December 19, 2022, at approximately 11:10 a.m., an accidental release of 22,000 pounds of anhydrous ammonia occurred from the NH3 refrigeration process at a food processing facility in Norwood, Massachusetts. Exposure to the toxic ammonia vapor fatally injured one contract worker and seriously injured another contract worker. In addition, the release caused about $4 million in property damage.
The facility had hired a contractor to install an electrical (ceiling-mounted) heater to replace an existing leaking steam heater that provided comfort heating inside the facility’s ammonia refrigeration machinery room. The work plan included using a scissor lift to access the installation area. At the time of the incident, two (2) contract workers were on the scissor lift to install the electric heater. While the scissor lift was in an elevated position, the lift was moved forward and then upward, impacting an ammonia refrigeration system valve.
After the scissor lift impacted the piping, a leak formed at the partially severed ½-inch threaded piping connection to the larger ammonia system piping. The anhydrous ammonia was released as a vapor, engulfing the workers. Contractor 1, who was directly in front of the damaged piping, was unable to escape and was fatally injured by the release. Contractor 2, who was further away from the point of release, jumped over the lift’s guardrail to escape from the area.
Two employees heard the release and saw the ammonia vapor cloud through a door window. One of these employees grabbed a two-way radio and instructed maintenance to initiate an evacuation of the building. Alarms in the ammonia machinery room and throughout the building were activated, alerting all employees to evacuate from the building. Evacuating employees found Contractor 2 outside the building. After checking on Contractor 2, one of the employees called emergency responders. Emergency responders recovered Contractor 1’s body from the scissor lift and transported Contractor 2 to a nearby hospital to treat his serious injuries.
Approximately 22,000 pounds of ammonia were released during the incident.
Probable Cause
Based on the facility’s investigation, the CSB determined that the probable cause of the anhydrous ammonia release was piping damage caused by the force applied by the scissor lift.
Source: https://www.csb.gov/assets/1/6/csb_incident_reports_volume_one_2025-01-14_rev_1.pdf