An explosion occurred in the early afternoon at a special liquid and solid industrial waste pre-treatment plant on a thermal dryer used for treating centrifugal hydrocarbonated sludge in order to eliminate water and residual hydrocarbons. The treatment was carried out at a temperature of between 180 and 190 °C obtained by the circulation of a heat-transfer fluid. The sludge was carried into the dryer by four augers encased in a double shell containing the heat-transfer fluid. The drying times vary between 1 and 2 hours. A negative pressure of 80 mm water column is maintained in the dryer. The gaseous effluents collected – a mixture of water and hydrocarbons – are burned in a boiler. At the time of the accident, air entering the gaseous atmosphere in the dryer may have created excess pressure in the device and led to the failure of some of the fastenings connecting the lower and upper parts on half of the outer casing. The upper part of the dryer was therefore partially separated from the lower part. Thick black smoke was released. The heating circuit and condensation circuit were isolated. The electricity supply was cut off. The emergency services arrived on site 3 minutes after the alert and controlled the fire within 30 minutes. All of the liquid effluents were recovered in the basin provided for this purpose. The operator has implemented several measures: monitoring of the self-ignition of the products upon delivery and implementation of a procedure, definition of the acceptable limit of waste according to the temperature of the heat-carrying fluid, implementation of a collection point for the periodic measurement of oxygen in the gaseous blanket of the dryer, reduction of the temperature of the heat-carrying fluid, reduction of the negative pressure in the dryer in order to limit the air intake according to the stability of the oxidator, and implementation of explosiveness and chromatography measurements in the gaseous atmosphere in order to establish a characteristic sample of the hydrocarbons likely to be found in this atmosphere(flash point).