In the spring of 2024, emergency responders responded to an ammonia leak at a cold storage facility in southern Ontario. The incident occurred on the roof, where a corroded shut-off valve on the hot gas line of an ammonia center evaporator failed, resulting in the release of ammonia gas into the surrounding environment.
The cold storage facility handles perishable goods for distribution across the region and uses ammonia as a refrigerant. The leak was discovered by neighbouring residents who sensed the strong ammonia odour and promptly notified the local Fire Department. Firefighters responded quickly, evacuating nearby residences and establishing a perimeter to contain the hazardous area. There were no reported injuries.
The Ministry of the Environment and Climate Change’s Spills Action Centre alerted TSSA to investigate the incident.
TSSA Analysis and Action
TSSA inspectors examined the ammonia piping system, focusing on the failed shut-off valve and its surrounding components. They conducted interviews with facility personnel, including engineers and maintenance staff, to gather information about the maintenance history and operational protocols related to the refrigeration system. The investigation revealed that the shut-off valve had corroded under the insulation, compromising three out of four threaded fasteners that were securing the valve bonnet. This corrosion weakened the sealing of the valve, causing release of the toxic gas.
According to TSSA’s data, 17 refrigeration plants were identified as high-risk in FY24, representing 22% of all high-risk plants. Among the top high-risk issues identified during periodic inspections of operating plants, problems with the maintenance or replacement of aged safety valves at refrigeration plants ranked second.
“Proactive maintenance and rigorous safety measures are essential in industrial settings,” said Adrian Van Maanen, TSSA’s inspector responsible for investigating the incident. “The risk of an incident like this could have been reduced through preventative inspection, including thorough checks under the insulation of critical piping sections that are susceptible to corrosion. By addressing potential vulnerabilities early on, we can work towards improved safety for both plant workers and the community.”
Source: https://www.tssa.org/sites/default/files/2025-04/TSSA_Public%20Safety%20Report_Apr%204%202025.pdf