In detecting an ammonia (NH3) leak around 2:45 am, a night watchman shut down the refrigeration installation of a poultry processing plant and then notified both the on-call staff and emergency services. Upon noticing an odd smell, neighbours residents also warned the local emergency services.

The installation was placed back online at 3:30 am, though the workforce was kept out of the building between 4 and 6 am. Following their gradual return to the workshops, several employees felt ill effects; one was hospitalised out of precaution. Fire-fighters requested the whole site be evacuated. During a follow-up survey, emergency responders measured a 30-ppm concentration of NH3 in the stormwater, which then had to be confined. A specialised firm scraped the collector pipes involved during the morning, in pumping 3 m³ of residual effluent.

The safety valve on the main discharge collector opened subsequent to malfunction of the pressure switch associated with the high-pressure compressor, which stopped shortly thereafter. The NH3 released into the atmosphere partially fell back onto the building roof and leached by rainfall. The stormwater network contamination then led to strong odorous emanations in certain workshops.

Since the NH3 was emitted outside of the machine room, the leak was not detected by the sensors located inside the premises, and the alarm was not relayed to the on-call technician’s phone; 150 to 200 kg of NH3 were lost of the 7,500 kg placed in the installation.