Fire broke out at 6 pm in one of the 4 electrical power cabinets supplying 3 melting furnaces at a cast iron foundry. This equipment had been installed in a 450 m², partially underground premises beneath the furnace access platform. Manual activation of the automatic CO2 extinction (3 bottles per cabinet) in the staircase accessing the premises 20 minutes after fire outbreak was not sufficient to extinguish the blaze: emergency services had to be called. The 60 fire-fighters mobilised could not access the fire source due to heavy smoke that ignited in the access staircase. While waiting for additional emulsifiers to arrive from neighbouring departments, the 70 tonnes of cast iron from the 2 operating furnaces were drained : 50 tonnes were collected in ingot moulds, the remaining 20 tonnes were stored in hollowed pits in the ground at the exit to the production workshop. The cast iron transfer step was completed by midnight. Fire-fighters then flooded half the premises with foam, as the volume of emulsifier available onsite proved sufficient. The fire was extinguished within 45 min. Property damage was substantial: inoperable furnace electrical supply systems, cracked furnace access platform. In all, 480 employees faced potential layoffs lasting 1 to 2 months. According to initial statements, the fire had ignited due to the ‘breakdown’ of one of the 144 oil condensers installed in each electrical cabinet. To ensure their fire protection, all cabinets were fitted over their upper part with 2 optical sensors and 2 coupled ionis detectors. On the day of the incident, optical detection was operable since the alarm had relayed near the furnaces; given that the ionis detection failed to provide confirmation however, automatic extinction was not activated. This condenser explosion most certainly damaged the ionis detectors, thereby preventing confirmation of the fire outbreak. Extinction was thus delayed by 20 minutes, the time it took to learn of the incident and manually trigger CO2 extinction, yet without knowing whether the device control was still operational. The operator commissioned appraisals and was required to submit a report to the Classified Facilities Inspectorate on causes of the accident and measures planned to ensure that such an event never repeats.