On an explosives manufacturing site, a fire broke out at around 4 pm in a 20 m² building reserved for the assembly of fireworks housing 47 kg of pyrotechnical products for a maximum stored or “stamping” of 100 kg. The assembly activities had been stopped in the workshops that same day at around 1 pm so that the 2 employees and the manager could have lunch. Given a high temperature (35 °C minimum), the assembly of parts was stopped as the workshops had to be emptied of the unassembled fireworks to be stored in appropriate buildings. During this transfer, a qualified fireworks operator (K4) noticed that a bomb was still equipped with its squib. Instead of cutting the fuse made of black powder before extracting it, he removed the fuse directly accidentally igniting the bomb with the appearance of sparks. The bomb in turn ignited the explosives remaining inside the rooms. The employee saw a white/yellow flash. The ejection device used for lifting the bomb during a launch was ejected, and only 3 s remained before the explosion… Within this time span, the technicians succeeded in pushing the machine back into the room, leave their work stations and raise the alarm. The building was destroyed: significant cracks in the walls, significantly damaged roof, melted natural lighting Plexiglas and warped sheet metal. Fragments were found 18 m away in an area describing an arc of a circle opposite the door. During the post-accident inspection, the inspector noted that the doors of all of the buildings were open, to the contrary of the requirements of the prefectural order specifying that warehouse doors should be kept locked outside of preparation or delivery periods. Given the atmospheric conditions (high temperature), the doors had been left open to limit the maximum temperature in the rooms. Security was provided by a member of the operator’s family, who should have made sure that the person assigned to this task was aware of the general safety guidelines (fire, emergency response, etc.). Resumption of the activity in the room affected was determined by the findings of the work safety report review. Separation of the buildings had helped to prevent the fire/explosion from spreading to the neighbouring rooms.