Patent ID: 7228871

Claim:
In a liquid petroleum storage tank containing at least gas that is at or near ambient pressure, a method for reducing formation of volatile organic compounds (VOCs) during filling of the tank, the method comprising the steps of: providing a liquid petroleum storage tank with a downpipe that has a non-constricted flow path along its entire length inside the tank; providing an inlet connecting the non-constricted flow path with the gas inside of the tank; introducing liquid petroleum that is at or near ambient temperature and pressure into the downpipe to fill the tank, thereby creating an underpressure in the upper portion of the downpipe compared to the pressure of the gas inside the tank; and using the underpressure to draw gas from inside the tank through the inlet and into the downpipe to thereby reduce the underpressure and reduce evaporation of the liquid petroleum as it is introduced into the tank.