In a refrigerated warehouse built in 1980, 40 kg of ammonia (NH3) leaked from refrigeration installations that were undergoing renovation and containing 3.5 tonnes of refrigerant.

At 10:20 am, before replacing the aboveground NH3 collector pipes in a material handling corridor, a pipefitter employed by a subcontracted refrigeration engineer removed heat insulation on several older pipes in front of the freezing tunnel. Upon finding ice inside the insulation, the pipefitter used a hammer and chisel but punctured a pipeline, causing gaseous NH3 to leak onto the handling platform. The head of operations issued an evacuation order for the platform and 5 min later for nearby offices; the site director, who was in the field visiting a client, was then alerted and instructed the head of operations to call in fire-fighters, notify the tenant using a portion of the premises separated from the NH3 zone, and keep personnel outside the building. From 10:30 to 11 am, the warehouse refrigeration engineer and 2 subcontracted employees closed the suction and liquid feed valves on both the cold storage rooms and tunnel. At 11 am, a technician accompanied 2 fire-fighters to search for the leak, which was localised 45 min later: a 2 to 3-mm hole on a collector pipe tap. The pipe was drained and evacuated. Air samples taken at 12:30 pm revealed: the absence of NH3 in the rented part of the premises, 0 to 4 ppm on the 1st floor of the warehouse, 4 to 20 ppm on the ground floor, and 50 ppm on the platform in front of the tunnel. Platform operations resumed at 1 pm. When the installation restarted, only the tunnel’s liquid service valve was insulated, with suction valves left open to remove NH3 remaining in the tunnel batteries.

The operator and subcontractor had drafted a prevention plan, along with an intervention procedure before commencing the works. No victims were reported. Several measures were adopted: replacement of the collector pipes and heat insulation, new collectors placed higher (reducing the risk of perforation) with heat insulators stored separately, meetings held with the subcontractor to review safety protocol and with the operating team to improve response to this type of accident, and a drill planned in collaboration with fire-fighters in 2006. A Prefecture order mandated a technical-economic study on NH3 distribution pipeline confinement in the vicinity of cold storage rooms, remote-controlled positive safety valves, and improved access conditions to raised installations within the distribution circuit.