Calorimetric and thermoanalytical methods were used to understand the reason why, during a distillation process, an explosion occurred in a solvent recovery plant. A sample of unreacted residue of the explosion was analysed by differential scanning calorimetry (DSC), thermogravimetry (TG), heat flux calorimetry and adiabatic calorimetry (ARC). The thermal stability of the residue was detected and the mechanism of the decomposition was deduced.