An ammonia leak occurred at a warehousing facility used by a supermarket chain. At 9:20 a.m., multiple technical faults were discovered in one of the facility’s chiller plants (chilled carbon dioxide/ammonia room). The room no longer had electricity, resetting was impossible and the anhydrous ammonia detection alarm went off and displayed thresholds of 40–120 ppm. The maintenance technicians searched for the causes. No ammonia odours were smelt in the room or nearby it. The chiller maintenance company was called at 9:40 a.m. At 10:25 a.m., technicians and the facility’s safety department noticed a suspicious odour outside the building. All 230 employees were ordered to shelter in place and the workers in the area in question were evacuated (13 people in three adjacent rooms). At 10:34 a.m., firefighters were called and the internal emergency plan was implemented. Upon arriving at 10:43 a.m., the firefighters confirmed that ammonia was leaking from a 494 kg tank and a puddle had formed on the floor. The second chiller plant kept the various cold storage rooms at the appropriate temperatures, thus preventing any negative impacts on the facility’s operations.

At around 1:30 p.m., the chiller maintenance company localised the ammonia leak on a compressor seal. It was sealed at around 9:00 p.m. The compressor was shut down pending the replacement of the seal. The room was returned to service at around 9:30 p.m. after isolating the damaged equipment. The compressor was repaired one week later (7 June) and the 5 kg of ammonia that had leaked out was charged into the equipment.

The operator introduced the following measures:

• technicians and members of the safety and prevention department received training from experts at the maintenance company on the chiller plant’s operation;
• anhydrous ammonia test kits were installed at the facility and employees received training on dispelling doubts;
• employees are now to shelter in place if future anhydrous ammonia leaks occur.