At 8:20 am, upon noticing that a greyish-white smoke was escaping from the upper part of his 24-m³, heat-insulated tank filled with divinylbenzene (DVB, a substance not covered in the ADR Agreement), which is a monomer used in the manufacturing of ion exchanging resin, the tanker car driver parked his vehicle on the emergency strip of the A26 motorway and sounded the alarm. At the time of their arrival, first responders noticed that the high pressure inside the tank had caused the set safety valve to open at 4.25 bar and moreover that the thermometer on the tank had been blocked at its maximum (115°C). By 9 am, they had set up a 400-m safety perimeter and shut down the motorway in both directions. The driver was not carrying any data sheets regarding the product being transported nor any emergency intervention instructions, thus making it impossible to quickly draw up an intervention strategy. The search for benzene and hydrocarbons in the smoke released proved negative. At 10 am, 3 representatives from the receiving company determined at the site that an exothermic polymerisation reaction had been initiated within the DVB mass during the maritime transport of the container from the U.S. to Antwerp and then by road haulage. According to other experts, the product contained an efficient polymerisation inhibitor in the presence of oxygen, with the oxygen available in the tank’s vapour space possibly being too quickly consumed during shipping (35 days) due to the high temperatures experienced during July; this hypothesis was confirmed at 7 pm that evening by the American supplier. The emergency crew hosed down the tank, which allowed the smoke to dissipate, but this did not serve to cool the tank’s loaded contents as a result of the heat insulation. Moreover, the tank’s coil was initially unusable for the purpose of cooling contents. A number of dams were installed in the pits as a preventive measure in order to confine the sprinkling water. Backup rescue personnel and an aerial reconnaissance team had been requested at 11:30 am. The Prefecture assembled a crisis unit by 12:30 pm. Upon decision of the Deputy Prefect, the crisis unit was disbanded at 8 pm that evening, then asked to reconvene as of 5 am the following morning. At 11 am the next morning, a pair of reconnaissance experts equipped with self-breathing apparatuses recorded a temperature of 180°C at the level of the tank’s manhole opening, though the actual tank pressure could not be determined without a manometer. Then, between 1:20 and 2 pm, with approval of the Managing Director of the receiving company, as confirmed by the CASU Emergency Response Unit, the tank was cooled by circulating cold water through the coil, allowing the temperature to be lowered to approx. 40°C. A manometer installed on the switching valve with the vapour space indicated a pressure of 0.5 bar. The tank was depressurised around 5:30 pm, then transported around 9 pm to its final destination. The motorway was gradually reopened to traffic until 11:50 pm. Another load of this same substance leaving the same plant, heading towards Scotland, would be involved in a similar incident on August 24th at the Port of Grangemouth.