At 9:40 a.m., two contractors were using an angle grinder to replace three air heaters connected to the heating system of a building at a plant that manufactures polyurethane foam board insulation. They were working near two drums containing 220 l of chemicals sitting on two drip trays. Buckets were under the tray to collect any leaks from system used to open the drum. One drum was filled with dioxolane (cyclic diether) and the other contained a plastics additive. Sparks produced by the angle grinder reached the ATEX zone above one of the buckets, causing an explosion that blew the bucket into the air and scattered its burning contents onto the operator, setting his clothes and back on fire. The second contractor suffered less severe burns. First responders and production personnel extinguished the flames on the contractor and on a nearby stack of insulation panels. The factory’s employees were evacuated. Operations resumed at the factory at 11:00 a.m.

An area of only a few square meters was impacted by the fire. The contractor who suffered severe burns on his back and head was taken by helicopter to hospital in Paris. The other one was taken to hospital. One employee was slightly injured whilst running to fetch the factory’s managers.

The prevention plans and hot-work permits, which indicated that protections had to be set up (fireproof tarpaulin) and barriers erected around the area, had been issued on the first day of the work (6 June). However, the barriers were removed at the end of the first day and not re-erected the following day (7 June). This resulted in the jobsite being moved. To access the site, the contractors had permission for the duration of their work (one week) to go through access-control gates that had been recently installed. On 7 June, they entered the site unaccompanied by any employees who could have told them that their jobsite had been moved after its barriers were not put back up. They took it upon themselves to begin working where their equipment was being stored, i.e., outside the area that had initially been marked off for the hot-work permit and near the drums of chemicals.

Since the accident, the operator now limits contractors’ access to the site to one day so that the site manager can approve this access and supervise contractors as they set up for work.

The inspection authorities for classified facilities required the operator to supplement its hot-work permits with instructions specifying that barriers placed around jobsites are not to be moved. The operator was also required to explain why the drums of chemicals were stored alongside the building where the contractors were working, i.e., beyond the area marked off for the storage of flammable substances.