A fire broke out at around 11○p.m. in a manufacturing plant specialising in surface treatment products. The fire detection system had operated correctly and the site’s designated on-call firefighters and the fire brigade were able to respond to the fire. The power utilities were disconnected and the water networks were blocked. The firefighters were able to bring the fire under control at about 2○a.m. using water and foam-based extinguishing media.

The very aggressive fire ripped through the surface treatment workshop and the treatment tanks located there, containing 360○m³ of toxic products (hydrochloric acid, fluorinated bases, and sodium hydroxide). Several adjacent premises, including chemical storage facilities, maintenance and offices, were also affected by the fire extinguishing water. A gas pipe on the building’s facade exploded and fell 30○m into the car park. Steel framework bent onto the structures used for handling operations, which in turn collapse onto the tanks. The neighbouring company, separated by a firewall, was not affected. Toxicological measurements in the atmosphere were negative, and the extinguishing water and pollutants were confined to the site. The results of the smoke toxicity measurements were not alarming. The fire was extinguished at around 4:00○a.m. No injuries were reported although the production facilities were destroyed, which resulted in around thirty employees being technically unemployed.

The fire was allegedly started on a PVC degreasing bath that had been drained for maintenance. A problem had occurred on the level sensor which remained blocked in the high position, preventing the bath’s heater from being switched off by the low-level sensor. The formation of sodium hydroxide crystals around the float is believed to have been the cause. No operational inspection of this sensor had been conducted while the bath was being drained. The time stamp, use for automatic heating control, has been programmed to allow the baths to be restarted on Monday morning. The production department decided to heat a specific bath that Thursday evening, although this bath was on the same programming schedule as the empty degreasing bath. Heating started at 11:00 p.m., as scheduled. The immersion heater came on in the empty bath and ignited the tank. The suction system, which was operating continuously, fanned the fire causing the rest of the workshop to burst into flames. It also fuelled the fire by burning and then collapsing back onto the equipment.

The operator has drafted a procedure to secure empty tanks by a system wherein the maintenance department can switch off the heating system at the switchboard. The procedure also includes systematic verification of level detector operation.