In a tyre factory, 30 l of hydrosol hexane (SKOL) leaked at 11 am from the upper inspection chamber of a 40,000 l tank during filling. The high-level audible alarm sounded with shutdown of the unloading. The emission of solvent vapours caused a risk of explosion during the time necessary for their dissipation: the product was highly volatile, but the external area was ventilated. The environmental impact was limited to an emission of VOC which could not be treated. The gatehouse was alerted. In-house firefighters and the safety manager set up a safety perimeter and stopped the circulation of vehicles in the area affected. The manager called the supplier and the product remaining in the road tanker was pumped. An analysis of the incident showed that a margin of 1,000 l had been taken in relation to the 40,000 l theoretical capacity of the tank; this margin proved to be insufficient. A problem was also revealed concerning the activation of the order for the product based on a forecast consumption of 5 days resulting in a delivery time that was too long. The gauge and the gauge transmission subsequently checked were not called into question. Following a CHSCT (Committee for health, safety and working conditions) meeting on 15/09/06, several measures were taken to prevent such a situation from happening again: margin of 2,000 l bringing the maximum useful level to 38,000 l, implementation of retraining sessions on the actions to take in the event of incidents for technicians carrying out the unloading operations, and renegotiation of a delivery time of 3 days with the supplier. The operator planned to extend this margin to the other storage tanks and schedule the training of any new employees so that they would be able to respond in the event of a malfunction before authorising unloading operations.