In a synthetic rubber factory, fire broke out around 1 am on the roof outlet vent of one of the 17 reactors located inside the polymerisation building. The facility activated its internal emergency plan. Backed up by fire-fighters upon their arrival, a first response team made up of production technicians sprinkled the building. The fire was brought under control around 2:15 am. After a thorough assessment of the situation by management in the presence of authorities (fire-fighters, Classified Facilities Inspectorate and a local elected official), the internal emergency plan was lifted at 2:45 am. The 25 factory employees were evacuated, as were all 138 employees at the neighbouring firm, one of whom was intoxicated. A pressure surge in one of the reactors, detected in the control room (4.9 bar instead of 4.2) caused the safety disc to break at the top of the reactor, which nonetheless had been designed to withstand 6.1 bar. The foamy reaction mix (128 kg of styrene, 122 kg of 2-vinylpyridine, 599 kg of butadiene and water) escaped via a bypass circuit whose valve had been left open by error. This mix spread over the roof and ignited. The specific reactor was isolated, allowing the other reactors to operate normally. Fire water was recovered at the level of the facility’s water treatment plant. No major environmental impacts were recorded, as the smoke generated from the fire was, according to the operator, similar to that of a flare. Property damage remained limited, with production losses estimated at €81,000. The Classified Facilities Inspectorate requested the operator to file a report analysing the causes of this fire. The alignment, reactor safety rupture discs and valves were all inspected.