At around 4.30 pm, a technician noticed flames on one of the 5 oil quenching installations of a bearing manufacturing plant. He acted immediately and extinguished the outbreak of fire in the tank, as usual, using a compressed air “blower”. A few moments later, a second employee noticed that the oil vapour and smoke exhaust duct, overhanging the quenching tank, had ignited; an in-house firefighter extinguished the fire using an extinguisher. The public emergency services, who arrived at the scene 15 min later, checked for any residual fires. There were no victims and only a section of duct was damaged. The inspection authorities for classified facilities carried out an investigation the next day. The exhaust pipe of every quenching installation was fitted with a fire damper, controlled by a thermal fuse. A fixed CO2 extinguisher, also fuse-triggered and combined with a manual control, was used to extinguish a fire between the oil bath and the closure member. On the day of the accident, only this closure member worked. It would seem that the fire was caused by the combination of 3 factors: an accumulation of combustible residues on the inner wall of the duct in particular in its horizontal section, which is several metres long and located downstream of the valve in the direction of flow, the closure member was closed too slowly and the automatic extinguisher was not activated. The thermal fuse offset in relation to the middle of the tank could not be activated by the fire. Following the accident, the operator made provisions to remind technicians of the guidelines, install additional extinguishers at the quenching station, check the temperature of the exhaust ducts, check that the safety plcs were working correctly and clean the ducts every 2 years. It also planned to begin studies aiming to eliminate the horizontal sections of the exhaust ducts, lower the quenching temperature to 45 °C (currently 50 °C) and define alternative solutions to using “blowers”. The inspection authorities for classified facilities asked the operator to provide a report on the accident, extend the new provisions to the quenching installations of its other sites and propose measures for improving the efficiency of the triggering of the fire damper and automatic extinguishing system.