Abstract: There is disclosed a method for the removal and recovery of hydrocarbons which are contained within the air/vapor mixture in bulk oil or gasoline storage tanks using fractional condensation with cryogenic cooling. The air/vapor mixture is flushed from the tank with fresh air and passed, successively, through several stages of a portable condenser train. When necessary, the first stage of the treatment comprises a caustic wash stage where the air/vapor mixture is contacted completely with a caustic solution to remove sulfur compounds. The desulfurized air/vapor mixture is then passed to the first condenser stage which condenses and removes substantially all moisture within the mixture. The de-humidified, desulfurized mixture is then passed to an intermediate stage where the heavier hydrocarbon fractions are condensed and separated and is then passed to a final condenser stage where it is cooled to a temperature of at least -100 degrees F., sufficient to condense substantially all hydrocarbon component therein.