A fire broke out at roughly 3:45 p.m. in an oven of a factory manufacturing soft silicone food moulds. The plant has four ovens that are indispensable for finalising the mould making process. The recent arrival of two new ovens in June led the operator to reorganise their installation on the premises. On 12/09, the two old ovens were moved to an empty room. On 14/09, the electrical power supply for the ovens’ general power cabinets was established, and the manufacturer’s technician confirmed the rotation direction of the ovens’ circulating motors. The next day, at roughly 3 p.m., after the extraction ducts from the ovens had been connected to the solvent vapour recovery network by another service provider, the head of the production workshop started up the two ovens empty. A fault occurred on one of the ovens, while the other one was operating properly. The person in charge then decided to put the moulds in the operating oven. When the door was opened, he noted that the heating elements were bright red and that the temperature was abnormally high. Having noticed smoke, he closed the oven, triggered the emergency stop and raised the alarm. The safety sensor, whose alarm set point was set at 240°C, did not trip. The temperature reading indicated 175°C. Smoke exhaust hatches were opened and the two employees working nearby evacuated the premises. At 4:05 p.m., the internal teams were able to bring the fire under control with eight CO2 fire extinguishers. The smoke was from the mineral wool used as insulation around the oven, 50 l had burned up, representing a financial loss of €2,400.

The fire resulted from an error in the rotation direction of the oven’s circulating motor, resulting in insufficient ventilation in the chamber. The safety sensor, placed at mid-height, did not detect the temperature rise at ceiling level.

A working group made up of the site manager, the head of the maintenance department and the production manager established a causal tree to validate the actions to be implemented:

• the safety sensor was moved close to the oven ceiling,
• an instruction regarding the restart the ovens after the supplier’s intervention or a moving operation was drafted to include verification of the rotation direction of the circulating motor, alarm testing, performance of an empty cycle and a monitored initial loaded cycle,
• the position of the safety sensors was checked on all the ovens,
• the maintenance contract for the ovens was updated.

Following a post-accident visit, the Classified Facilities Installation Authorities noticed the following:

• non-declaration of modifications to the layout of the oven room and packaging area,
• incomplete ATEX zoning.