Abstract: A vent system for a fuel storage tank and a pressure vacuum valve (PVV) module for use with such a vent system are disclosed. The vent system defines a vent path from the fuel storage tank to atmosphere. An elongate vent pipe extends vertically to a rain cap located at the upper end of the vent pipe. A pressure vacuum valve (PVV) is located in the vent path between the lower end of the vent pipe and the tank. The pressure vacuum valve maintains the vent path in a closed condition unless the pressure in the tank is above or below a predetermined pressure. By separating the PVV from the rain cap and placing it between the lower end of the vent pipe and the tank, it is possible to site the PVV at an accessible level for maintenance.