At 4:10 am, a violent explosion erupted in the main workshop (400 m²) of a factory specialised in manufacturing and packaging detergents. The blast was followed by a fire outbreak brought under control by fire-fighters dispatched to the site. The 50 m³ of extinction water were channelled into a (200 m³) basin. According to the operator, this accident happened on a mixer (9 m³ capacity) dedicated to producing peracetic acid (disinfectant, steriliser in the food processing and hospital industries). This product was obtained at atmospheric pressure by cold mixing 50% acetic acid, 28% H2O2, 5% various additives and 17% water. At the time of the accident, the mixer held approx. 1.5 m³ of solution prepared the previous day and intended for packaging the following morning in plastic drums. Since all production onsite took place during the day shift, no employee was present when the explosion occurred.

Property damage was extensive: collapse of the roof composed of asbestos cement sheets, potential collapse of the structural frame, shredding of the stainless steel mixer due to the power of the explosion. Given the state of the building frame and roof, first responders prohibited access to the workshop, as the risk of falling metal parts and asbestos cement sheets was very real. According to the appraiser commissioned by the operator, the introduction of a (metallic?) contaminant into the mix upon sample extraction caused the peracetic acid to decompose and initiated the runaway reaction, which was unstable at room temperature. Since the energy released was unable to dissipate, pressure rose until bursting of the tank, which had not been equipped with an internal pressure surge limiting device. Adopted on 28th July, an order assigning emergency measures made workshop restart contingent upon verification of the structural integrity of the building, facilities and equipment, etc. Moreover, this order imposed securing access conditions to the compromised installations, the site (fence, site protection), all containers capable of generating risk, and the removal of extinction water and damaged products. Since the process proved unstable at room temperature, the appraiser proposed a process analysis, monitoring of the reaction medium temperature using both servo-controls and an alarm, installation of vents on the mixer and a rupture disc connected to a catch tank, and personnel training in the use of peroxides.