At around 2:00 p.m., a fire broke out on the plastic siding of a building at a chemical plant. The flames spread along the full height of the building, which was located away from the production units. As the roof was made of non-combustible materials, only the plastic siding panels burnt. Firefighters contained the fire after two hours. The 35 employees present were evacuated at around 2:30 p.m.

No hazardous materials were affected by the fire. At the time of the fire, the building contained sulphur belonging to a neighbour (it was being rented out for storage purposes). All the materials inside the building had been moved more than 10 m away from its walls. The environmental impact was limited to combustion gases emitted by the burning plastic panels. The firewater was contained in the site’s internal sewer network.

The fire was caused by a blowtorch that was being used to remove metal components from a wall in order to install metal siding onto the building’s façade. The hot-work permit procedure had not revealed the presence of a disused cable tray (hidden by the plastic siding) or that the work had to be performed several metres above ground, requiring the use of a cherry picker. Although the areas where cutting was being performed were wetted as required by the hot-work permit, the cables in the tray ignited and the flames spread to the building’s plastic siding.

A fault tree analysis found a number of issues:

• the risk analysis performed as part of the hot-work permit was inaccurate and did not detect the risk associated with the cables.
• intermittent wetting due to the organisation of work: while the protocol called for continuous wetting to improve cooling, cutting and wetting had been performed by the same technician, who worked alone on the cherry picker.
• the technician underestimated the risk involved.
• a need to improve the site’s procedure for controlling hot work and its training of employees charged with issuing these permits.
• a need to improve the supervision of hot work and match resources with the instructions to be followed during this supervision (supervisor training).