In an aluminium (Al) foundry, fire broke out while cleaning dust extraction equipment installed in a shot blasting unit. The accident occurred as the foundry was shutting down normal activity and initiating its annual maintenance programme. The shot blasting facility suddenly ignited as a technician was cleaning Al dusts by blowing them with compressed air. Opening of the explosion protection vents then provided the means for the blaze to spread to the roof. All electrical, automated and hydraulic machinery was turned off and secured. In accordance with guidelines adopted after a similar accident 2 years prior, first responders did not sprinkle the dust extraction system or shot blasting machine, confining their intervention to sprinkling the roof and its supporting metal beams. These lessons enabled responders to control the fire within 15 min. The extinction water was recovered in the foundry’s detoxification plant. Physical damage was extensive: 100 m² of roof requiring repairs, electrical installations compromised, and an inoperable dust extraction system. The foundry owner sought replacement solutions (i.e. subcontracting, equipment substitution), which would have implied significant outlays, so as to avoid jeopardising production. The operator was served a Prefectural order imposing a number of emergency measures. According to the Classified Facilities Inspector, a major pressure rise (due to explosion?) caused the explosion hatches to open. The cleaning technique responsible for sending dust particles into suspension and potentially forming an explosive and flammable cloud was reassessed. The dirty condition of the roof, which facilitated the spread of the fire, was also cited. As instructed following the 1st accident, the check valves installed on the pipe connecting the shot blasting machine performed effectively.