At around 1:00 a.m., an operator working on the finishing shop of a pharmaceutical plant heard an unusual whistling noise and saw smoke coming out of an expansion bellows while wet crystals were being dried in a 1600 l stainless-steel dryer/mixer. He alerted the on-site firefighters, who sprayed water into the smoke to knock it down and protect the other buildings. They then entered the shop and doused the inside of the equipment with water. The drying temperature had swung between 42 and 53 °C at the start of the reaction, then suddenly shot up to 200 °C. After several hours of monitoring, the charred mixture lowered to normal temperature.

The facility suffered damage (vacuum pump, spattered product) estimated at €100,000 (excluding operating losses). It took the plant operator several weeks to clean the equipment and accessories, perform differential scanning calorimetry (DSC) on the starting materials and the burnt product, and check all the operations performed prior to the batch that started the fire in order to determine what caused the product to completely combust. It concluded that a bearing in the conical mill of the dryer/mixer failed. This failure resulted in friction, which caused the product to heat up locally and combust. The combustion then quickly spread to the rest of the product due to the high energy potential of the reaction.

The operator plans to implement stricter preventive inspections of equipment bearings. An analysis of the risk of sensitivity to friction and the propagation tendency of reactions will be performed for products with high energy potential (identified with DSC). The capacity of the dryers will be adjusted according to the results.