At around 7:15 p.m., an explosion followed by a fire occurred in a 50 m² storage building at plant that manufactures synthetic substances for the chemical and pharmaceutical industries. The following were stored on pallets:

• metal drums of propargyl alcohol (flammable and toxic);
• fibre drums of nonconforming substances containing solvents;
• bags of calcium chloride and sodium chloride.

At the time of the incident, the plant was shut down for maintenance. The storage building was used to store toxic substances. In addition, nonconforming finished products were being temporarily stored there for work. A security guard gave the alert after hearing the explosion. Black smoke billowed out of the building. Firefighters brought the fire under control at 7:40 p.m. A leak on a nitrogen line was stopped. The firewater was collected in a retention pond and then treated at the site’s wastewater treatment plant.

The substances stored in the building were destroyed. The power supply of the VOC treatment system’s thermal oxidiser was severely damaged, rendering the system inoperative. The tank used to add nitrogen to the headspace of the solvent tanks was no longer able to do its job. It was returned to service 48 hours later.

Two days after the incident, the inspection authorities for classified facilities suggested that the fire may have been caused by the temporarily stored substances, for which the associated risks had not been analysed, and by grinding work that was underway at the time. The site had received a formal notice the previous year for deficiencies in its management of chemicals. The operator ruled out this possibility after investigating the fire’s causes with an expert.

After an expert assessment of the drums, the operator determined that the fire was caused by the explosion of a drum of propargyl alcohol (flash point below 60 °C) that had polymerised after being stored for a prolonged period at ambient temperatures of over 30 °C. The substance’s material safety data sheet (MSDS) mentioned protecting the substance from heat and avoiding exposing it to temperatures above 80 °C, but it did not specify this particular risk.

The operator took the following corrective actions:

• changed the storage conditions for propargyl alcohol: opened drums are to be stored under nitrogen and disposed of as waste after two or three weeks, unopened drums are to be stored indoors at less than 30 °C and for less than one year;
• checked the storage areas reserved for reactive or heat-sensitive substances;
• completed the thermal stability data for raw materials;
• set up a system that makes it possible to know inventory levels and changes in substances stored in the buildings at all times.