Abstract: A vapor recovery system for a fuel storage tank. The system includes a pair of VOC adsorbent canisters that alternately recover VOC vapors from the fuel tank ullage or are regenerated. Regeneration of the VOC adsorbent canisters is provided by exhausting the VOC vapors from the VOC canisters using a vacuum pump and back into the fuel tank ullage. When the operating pressure of the fuel tank ullage is elevated, an auxiliary VOC adsorbent canister is operated in parallel with the pair of canisters in order to recover the increased amount of VOC vapors in the tank ullage.