A dust explosion occurred at the level of a cyclofilter on a sanding line of a classified panel plant (Authorisation). Fire-fighters extinguished the subsequent blaze as it began to spread, in addition to performing comprehensive site surveys and thermal camera probes of the 3 silos connected to the damaged facility. Property damage was estimated at €180,000 while operating losses amounted to €192,000. The accident arose following the immobilisation of a panel with a sander, as the next panel on the line overtook the first one and jammed as well. Since both panels were in pressurised contact with the rotating abrasive belts, they caused self-heating of wood particles that, when stripped, triggered the explosion inside the cyclofilter. Malfunctions in the automatic extinction system had been logged. The Classified Facilities inspector’s investigation revealed that the panel lining protection system, placed at the beginning of the sanding line, was not operational. The calibration of a spring had in fact been excessively modified by a technician, thereby preventing the mechanism from being activated at the end of stroke, and this mechanism would have served to stop the 2nd panel before it entered the sanding line. The operator closed access to calibration adjustment (by welding) and informed plant personnel of the exact causes of this accident.