Fire broke out in a wood panel factory at around 5 p.m. in an 800 m³ concrete silo (height: 26 m, diameter: 8 m) containing 240 t of sawdust used to supply a biomass boiler. The internal emergency plan was activated, and the silo’s sprinkler system was switched on. The temperature in the silo was estimated at 250 °C. The emergency services decided to drain the storage container using the worm screw in the bottom of the silo.

An intervention in the long term …

The sawdust caught fire at 3 a.m. the next day. Falling blocks of sawdust caused several thermal flashes, so the firefighters decided to flood the interior of the storage container to reduce the flames. The situation worsened at 6:30 a.m. as the emptying operation continued, when the silo burst into flames over its entire height, causing the destruction of the worm screw and causing cracks to appear at the top of the silo. Faced with the risk of the silo collapsing, a safety perimeter of 60 m was set up. Spraying inside the silo was resumed. As the emergency services continued to cool down the silo from the outside, several explosions occurred inside the cell. Holes were made to remove the sawdust. The fire was put out on 01/11 at 10 a.m.; 4000 m³ of water had been used during the operation. As the site’s containment area was insufficient, part of the firefighting water, heavily loaded with suspended solids, was sent to the containment area of a neighbouring site.

During the extinguishing operations, one firefighter was severely burned after a pile of incandescent sawdust fell on top of him. Two others fell ill due to the fumes from a generator set. The manufacturer evaluated its losses at €1.000,000 (operating losses: shutdown of the site for 2 weeks, property damage, treatment of the firefighting water). The cost of firefighters’ intervention is estimated at € 32,000. The worst was nevertheless avoided: the fall of the silo on the boiler building which would have cost more than 10 M €.

The incident seems to have been caused by a fire going into a cyclone after a stripping operation. The scenario of a silo fire was not addressed in the site hazard study. In addition, the facility’s POI included an explosion scenario for the silo but no silo fire. Following the event, the operator reviews its extinguishing procedures and improves the management of fire safety on its site. Staff are also trained in new practices. On the technical side, cyclone tamping and temperature sensors with real-time control room reporting are installed. Firefighters are also drafting an intervention book on silo fires.