Fuel tank venting system for reduced fuel permeation

The present invention involves a venting system for venting a gaseous fluid from a tank having an aperture and a fuel delivery module cover. The tank is made of a predetermined material. The venting system comprises a venting valve for venting gaseous hydrocarbon fluid at a predetermined pressure from the tank. The valve is disposed through the aperture to define a circumferential space between the inner side of the outer lip and the venting valve. The system further includes a cover comprising the predetermined material and attached to the outer layer to seal the valve between the cover and the outer layer. The system further includes a retention member disposed about the venting valve and attached to the outer layer about the outer side of the outer lip defining an expansion boundary so that the outer lip only expands toward the venting valve to seal the circumferential space when the tank absorbs hydrocarbons.