A device for venting fuel tanks, especially of automotive vehicles, of the type having a volume equalizing vessel arranged in an upper zone of the interior of the fuel tank that communicates with the atmosphere is provided with inertial operated blocking members for sealing orifices into the equalizing vessel that are disposed at an upstream side of the orifices into the equalizing vessel relative to the interior of the tank. Additional venting conduits may be provided that are preferably inclined height wise and may either be mounted interiorly of the equalizing vessel so as to extend outwardly through an end wall thereof into close proximity with an end wall of the fuel tank or may be externally formed as a unitary formation of the equalizing vessel. An auxiliary sump chamber may be provided in a central portion of the auxiliary chamber bottom wall beneath the conduit venting the equalizing vessel to the atmosphere so as to ensure spillage therethrough during righting of a vehicle containing the fuel tank from an inverted position.