Pollution
Humain
Environnement
Economique

Fire broke out in a 60 m³-silo half-full of polyurethane dust, in a Seveso-classified plastic insulation panel factory. At approximately 14:00, there was an explosion in a polyurethane panel crusher; its expansion within the silo increased the pressure and one of the outlet vents gave way, causing a second explosion noise. Subsequently a fire broke out, releasing smoke and gas, including carbon monoxide (CO) and hydrogen cyanide (HCN). The alarm was set off at 14:05; 80 staff members were evacuated and the internal emergency plan (POI) was deployed. The internal safety teams made use of a factory fire hose and called the external emergency services at 14:15, who arrived between 14:30 and 14:45. The power supplies to the site were cut off and rainwater-network blocking valves were activated. The police force and gas, electricity and rail service representatives, as well as the deputy mayor and sub-prefect arrived on site. At 15:30, safety representatives evacuated the industrial and commercial zone (26 persons) and restricted movement for 500 local residents. A safety perimeter was established around the site. Fire service officials, equipped with self-contained breathing apparatus (SCBA), cooled the silo with fire hoses. Foam was injected from above. The undertaking does not have any technical drawings of the silo at its disposal. The maximum hydrogen cyanide concentration recorded was 4 ppm, compared with the exposure limit value of 1.9 ppm. The extinguishing water overflowed the retention structure but still remained contained on site, retained by the waterproof external courtyard. At 19:00, power lines were reconnected and one production line resumed operation. The fire was fully extinguished at 22:00. At 01:00 a second production line resumed operation. During the emergency, one firefighter was affected by carbon monoxide. With resources from other departments, a network to measure the level of hydrogen cyanide in the affected area could be set up. The following day, at approximately 10:00, once the hatch had been opened, SCBA-equipped firefighters emptied the silo from the bottom. This work was then taken over by a private company. The inspectorate responsible for classified facilities attended the scene. The safety services completed their work by 20:00. There was only limited damage to the site: The cladding panels of a workshop were blackened by smoke and the crusher was slightly damaged; the silo can be repaired. All production lines, which were shutdown for a few hours and which remained intact, resumed operation on 15 November. The silo in question is used to store two forms of polyurethane dust waste: fine machining dust aspirated off and passed via a bag filter before being transferred to the silo and coarser sawdust particles aspirated off as waste from a polyurethane-panel crusher located directly adjacent to the silo (linked by 20 m of tubing to enable aspiration from the crusher to silo). The dust particles are ultra light, weighing 450 kg per 30 m³. Given the site layout, it is unlikely that the machining section caused the fault (given the intermediary transfer via the filter, the duration of the aspiration process, absence of metal components, etc.). It is probable that the crusher was responsible, considering the fire marks on that device and the fact that crushed panels contain a fine layer of aluminium that could have generated a spark. Moreover, the crushing of panels releases pentane, which can be explosive or flammable under certain conditions, such as, for example, when a crusher heats up. These panels are often the source of fires breaking out in storage containers during crushing. The operator examines these hypotheses in the accident report. The operator is looking into installing a spark detection system in conjunction with a valve diversion or water sprinkler system. Further measures are envisaged: increasing air dilution in the crusher area, installing pentane detectors, and installing a belt or screw conveyor for the open-air evacuation of crushed panels. The crusher will not resume operation until the completion of corrective and preventative measures, the implementation of which will be monitored at the next meeting of the Health, Safety and Working Conditions Committee (CHSCT).