Inside a refinery depot subsequent to mishandled supply of a tank containing 7,000 tonnes of naphtha (and perhaps also due to the weight of snowfall), the tank’s floating roof became immobile and then sank. A technician sprayed foam onto the tank in order to limit evaporation of the product, but the foam was applied erroneously (as a result of inadequate training/instructions/procedures for emergency situations) in the middle of the tank surface rather than at the periphery. The static electricity charges produced then ignited naphtha/air vapours. Given the low ambient temperature (0°C), flash was not produced and the vapours ignited progressively as they were being released. The site’s emergency response plan was triggered, and both internal and external rescue teams fought the fire for 3 hours before its extinction. No impacts could be observed on the environment. Following this accident, the set of communication procedures as well as instructions and training on static electricity charges underwent revision.