A fuel storage system (10) is provided including a storage tank (12), an exhaust port (14), a filter system (14), a primary pump, and at least one secondary pump. The storage tank includes a fuel delivery port (18), a fluid vent port (20), and a pollutant return port (22). The filter system comprises a filter input port coupled to the fluid vent port (20), a fuel vapor duct, and primary and secondary filter output ports. The fuel vapor duct defines a flow path extending from the filter input port to the primary filter output port. The primary filter output port is coupled to the pollutant return port (22). At least a portion of the fuel vapor duct forms a permeable partition designed to pass a non-pollutant component of fluid within the fuel vapor duct through the permeable partition and designed to inhibit passage of a pollutant component of fluid within the fuel vapor duct through the partition. The secondary filter output port is partitioned from the fuel vapor duct by the air-permeable partition and is coupled to the exhaust port. The primary pump is positioned to cause fluid to pass from the filter input port to the primary filter output port. The secondary pump is positioned to cause the non-pollutant component within the fuel vapor duct to pass through the permeable partition to the secondary filter output port and the exhaust port.