At around 6.30 a.m., a fire broke out on a bar of polyurethane foam in a mobile storage building at a plant manufacturing plastic technical parts. The fire spread to a second bar. The forklift truck operator raised the alarm. At the same time, the sprinkler alarm was triggered. The operator triggered its internal emergency plan and 48 people were evacuated. Firefighters brought the fire under control at around 8.20 a.m. When on-site power supplies were turned back on, the sectional valve opened allowing the water used on the fire to spill into the nearby road for 30 minutes. Traces of pollution were visible over a distance of 200m. The production loss was estimated to be €26,812. The damage done to the mobile storage was estimated to total €15,000. Both bars were destroyed. 7t of burned or wet foam were transported to a disposal facility for burial due to the volume of foam blocks. 600m³ of water used on the fire were contained in flexible retention tanks. A similar event had occurred in the 1970s.

Lengthwise cutting of the bar revealed holes and blackened colouring in several places. The temperature had increased sufficiently in the centre of the foam for it to burn, creating chimneys in places. When the chimneys reached the external surface of the foam bar, the oxygen in the air allowed flames to appear. The flames rose up and spread the fire to the bar above.

The fire was due to an exotherm on the bar. The causes leading to the fire were the following:

• the large size of the bar (2m wide, 1.2m high, 65m long) which led to slower temperature decrease than on smaller bars;
• failure to detect block temperature monitoring anomalies;
• a possible issue with the quality of the polyol, which contained an insufficient quantity of antioxidant, which may have destabilised the reaction.

Following the event, the operator put in place the following actions:

• improving bar temperature monitoring with a remotely accessible system and alarm transfer to the guard room;
• locking out the sectional valve and displaying instructions on the valve;
• training the site’s security guards;
• checking emergency numbers with the town hall;
• training second intervention team;
• conducting valve, closure, and power cut-off tests.

Pending the polyol analysis results and testing, production of large bars was suspended.