An explosion and a fire occurred at a wood panel plant. Shortly before the accident, sparks were detected in the ‘4/dryer’ circuit which transports the dryer’s fibre to the forming area and in the ‘5/dryer’ circuit which recovers the fibre from cyclofilter Y28. Circuit 4, equipped with a fire extinguishing system, was wetting the fibre, causing stains on the panels and therefore shutting down production. The employees sprayed circuit 5 and noticed nothing abnormal. The explosion that occurred at 11:20 pm in cyclofilter Y28 when the fan was restarted, generated large flames which spread to cyclofilter Y27 and to the dryer room. The employees controlled the fire using internal equipment before the arrival of the public emergency services at 11.35 pm. At the operator’s request, the fire-fighters used an infra-red camera to check the exhaust ducts, where they detected no incandescent residue. The cladding and insulation of the dryer room were partially destroyed, all of the sleeves of cyclofilter Y28 had burned, the inspection hatches for cyclofilter Y27 were deformed and a compressed air pipe had been severed. New sparks were detected in the same circuits 2 days after the accident. Using infra-red cameras, the fire-fighters noted the presence of hot fibres in the upper internal part of the fan on cyclofilter Y28. A hole in the fan wall had caused the build-up of fibres in this location. The fan was repaired and the installations were progressively switched back on. One month later, during the annual shutdown for maintenance, the operator modified the shape of the upper part of the fan for cyclofilter Y28 in order to prevent any build-up of fibres and thoroughly checked the other fans.