Gasoline bulk storage tanks release reactive organic gas (ROG) vapors containing listed substances into the atmosphere. The majority of emissions can be categorized as bulk storage tank fitting losses, rim seal losses, working losses, deck seam losses, degassing releases, and refilling losses. Emission rates are highly dependent upon the storage tank size, construction, and design as well as annual fuel throughput. Most bulk gasoline storage tanks in San Diego County are equipped with either internal or external floating roofs. Fixed roof tanks are best quantified with the standard gasoline dispensing and storage procedures which can be modified to apply to any individual site's equipment and procedures.