In a workshop producing para-tert-butylbenzoic acid at a chemical plant, fire broke out at 5:08 am on a heat transfer fluid pipeline connected to the building’s boiler. The 2-storey, 700 m² structure, which housed on the ground floor a heat transfer fluid boiler and a refrigeration installation using chloro-fluoro refrigerant, was located in a high-risk zone by virtue of the presence of many pipelines containing hazardous substances (toluene, gas, etc.) in the vicinity. The facility director activated the internal emergency plan. Two fire-fighters present onsite began battling the blaze. A fire wall prevented spreading of the outbreak to the rest of the plant. The combined intervention of the internal crew (6 fire-fighters, 10 emergency service personnel) and external resources (90 fire-fighters, 19 vehicles), called as backup, made it possible to control the fire in 2 hours. The extinction water was confined to a 24,000 m³ basin located onsite. The causes of this incident could not be elucidated. Having fallen from a lorry during the emergency intervention, 1 internal fire-fighter suffered from back pain. Property damage, though limited to the building containing the boiler, extended to the building’s structure: slumping of the upper floor under the effect of heat. The Classified Facilities Inspectorate requested the operator file a detailed accident report indicating: the fate of extinction water and fire debris, the impact of this fire on the building’s structural stability (outer walls, inner walls, etc.) and on substance transport racks and pipes (gases, nitric acid, toluene, etc.). Plant activity was stopped for the rest of the day before resuming the next day.