Around 1 am at a wood panel factory, a field operator was called to service a condensing boiler designed to heat presses. The expansion vessel containing thermal oil at 274°C was 72% full despite the protocol stipulating a filling rate of between 40% and 50%. The field operator drained a portion of the expansion vessel into a tank containing oil at 60°C. After pouring out 2.5 m³ of product, he called the control room, which confirmed that the drainage step could be stopped. As he was preparing to climb back down into the retention basin with his back turned to the tank, hot oil vapours ignited and severely burned his legs, neck and face. He was wearing the appropriate individual protective gear. Vapours emanating from an elbow vent on the tank had fallen into the retention basin. A streak of flames had spread from the bottom of the tank into the circulation pump room before extinguishing on their own.

The crew foreman notified first responders and a rescue team attended to the victim. The thermal fluid circuits were drained in accordance with emergency procedures. The victim was helicoptered to a specialised burn unit.

Several possibilities are considered to determine the source of ignition of the fire:

• factory telephone (the operator did not have his personal telephone with him);
• static electricity caused by his reflective waistcoat
• friction from safety shoes;
• defective electrical equipment or dust accumulation…

The injured person did not have a personal lamp and the lighting in the area is permanent, and he did not operate a switch.

The factory operator modified the tank vent by adding a roof hood and installed a hydrocarbon sensor and air extractor in the retention basin, in addition to a camera to prevent field operators from stepping down into the tank to perform visual inspections. It was also anticipated to motorise the valves or control them remotely.