While making rounds at a storage tank facility, a watchman noticed a smell of crude oil. Since this observation coincided with filling a storage tank with crude, a fellow employee inspected the tank and reported that the floating roof was entirely covered by crude. The initial measure adopted was to halt the ongoing tank supply. For safety and environmental protection reasons, fire-fighters spread out a foam carpet. Hydrocarbon and H2S measurements taken immediately thereafter did not indicate any noticeable concentrations. Only a slight odour could be perceived at the site before foam was implemented throughout.