An unusual smell of gas, similar to that of butadiene, was detected at around 9.30 am in the “Mixture preparation” workshop of a rubber goods plant. It came from a latex tank filled that morning using a mobile latex tanker, and an aqueous dispersion of styrene-butadiene at 66%, unloaded at around 9 am. The site’s safety manager alerted fire services, in order to take explosive gas readings in the area. At the scene 15 min later, firefighters recorded low explosibility (10% of the lower explosion limit) in the tank, but there was no risk of explosion in the workshop. Firefighters specialising in technological risks, called as backup as a precaution, detected similar explosibility in the tank, but also recorded a high concentration of carbon monoxide (CO) equivalent. However, no trace of CO equivalent or risk of explosion was detected in the rest of the workshop. Nevertheless, it was evacuated and a safety perimeter was set up, then the power supply was cut off. Ten people who may have been exposed underwent a respiratory check, and only one person was hospitalised for further tests; no respiratory problem was detected. Firefighters continued the atmospheric controls in the tank and in the workshop which was ventilated. The hydrocarbon concentration was measured on a sample of latex; the value recorded, which was positive, seemed to indicate that the latex contained unpolymerised butadiene or another non-polar hydrocarbonated compound. The analysis also enabled the presence of CO to be excluded. No variation in concentration in the atmosphere was recorded, the firefighters authorised access to the workshop at 3 pm and removed the safety perimeter. Further examinations were carried out on the latex to determine the source and nature of the pollutant: incorrect manufacturing process, carrier’s tanker not cleaned properly, etc. The operator also took samples in order to study the quality issue with the supplier. The contaminated latex was assessed internally and used that evening. An unloading error caused the incident; the driver first connected the bottom of the truck’s compartment that contained heptane, then unloaded the 2 other compartments containing latex before leaving the site without telling anyone. The driver acknowledged the facts a few days after the analyses. Several measures were established by the manufacturer and its carrier: specific driver training, the affixing of removable labels on the compartments of tankers containing latex.