A fire broke out at 6:09 p.m. on the outdoor dust collector of a shot-blasting machine at a Seveso-classified plant that manufactures and maintains aircraft landing gear. The unit’s 250 employees were evacuated and the public firefighters were called in. The onsite safety responders used a fire hose reel and the dust collector’s CO2 extinguishing system to bring the fire under control. The firefighters arrived on the scene at 6:34 p.m.; at 6:45 p.m. they considered that the fire was out. The extinguishing water collected in a containment was pumped out and disposed of by the contractor that removes waste from the site. The gendarmerie and electric utility arrived on the scene. The plant operator, assisted by a specialist engineering and design firm, conducted an investigation to determine the causes of fire. Three possible scenarios were postulated:

•  Self-heating of dust. However, this seems unlikely because not many titanium parts are shot-blasted (around one per month).
•  Electrostatic discharge between components of the dust collector, despite being earthed.
•  A mechanical spark. An employee (who lives near the facility) reported having heard sounds of metal on metal shortly before the fire. However, no suspicious foreign matter was found during the investigation.

The plant operator implemented a number of measures before restarting the shot-blasting machine on 10 July. New filters with higher conductivity than the previous ones were fitted. The earthing of the facility was improved by fitting equipotential bonding conductors between the ducts, filters, dust collection tanks, and the body of the shot-blasting machine. A solenoid valve was installed on the dust filter air-cleaning system, which is controlled by the facility’s emergency stop. The dust collector outlet was fitted with an inspection hatch to allow periodic cleaning. Safety wire was applied to fastenings inside the machine. Lastly, the CO2 fire extinguisher was replaced.

The engineering and design firm updated the ATEX studies (which dated back to 2007) for the two other shot-blasting machines. In addition, the plant operator drew up instructions for using the CO2 fire extinguisher and increased the awareness of the relevant workers. It also contacted suppliers to retrofit the dust collector and move the manual control used to trigger the CO2 system. It also planned to conduct a feedback session with the various responders.