Inside a pyrotechnic plant, an explosion occurred on a granulation machine dedicated to a fireworks pyrotechnic composition (a boron/nitrate mix, with a 1.3.a classification). A very intense combustion followed, along with a slight blast. The technician sustained very severe burns (3rd degree at the level of the abdomen and thighs). The wall of the honeycomb chamber was blown apart and the machines inside were seriously damaged. The accident happened when plant machines were undergoing cleaning following a period of operations. A large quantity of active material (2 kg) would have ignited in response to a shock. According to initial investigation findings, the procedure applied had called for discharging all active material prior to machine cleaning, but this precaution had not been respected. The operator increased personnel awareness to this procedural step and analysed the machine design as well.