A fire occurred at 4 am on a pellet packing machine for chlorinated detergents (sodium dichloroisocyanurate dihydrate – DCCNa) on the ground floor of a 2,000 sq.m chemical plant; it began spreading via the machine’s suction duct to mixture tanks on the floor above. Heavy smoke formed a chlorinated cloud that was pushed by winds blowing from the north and north-east. A safety perimeter was set up and the residents of 6 towns (Saint-Just-Saint-Rambert, Andrézieux-Bouthéon, Sury-le-Comtal, Chambles, Saint-Cyprien, Saint-Marcellin-en-Forez and Bonson), alerted by loudspeakers on cars and by local radio stations, were told to remain indoors. Nonetheless, the chlorine (Cl2) measurements taken by fire-fighters within a 1-km radius around the site only revealed weak concentrations (a few ppm detected). Measurements recorded inside the cloud by a civil protection helicopter also indicated small Cl2 concentrations. The massive fire-fighter intervention, complete with a large set of hydraulic equipment, served to limit the quantity of product consumed to 350 kg of the 10 tonnes stored onsite. The site’s stormwater drains network was plugged in order to avoid pollution to the adjacent watercourse. The confinement plan was lifted 4½ hours after its activation and 7½ hours after fire outbreak. The fire extinction water (142 m3) was pumped for treatment by a specialised firm, as were the recovered solid wastes (27 tonnes) and chemical wastes (28.5 tonnes). No victims were reported either inside or outside the facility. No environmental impacts were recorded. The fire was caused by heating of the filling camshaft and holes punched in the machine from contact with powder fouled by both lubricating oil and iron filings. Several measures were adopted, namely installation on all pelletisers of a high temperature safety device (50°C), placed on each line associated with the filling camshaft; verification of the absence of powder on the lower part of the machine every 8 hours and absence of oil on the rotating tray of each workstation’s pelletiser; updated procedures ordering production shutdown in the event of any anomaly.