Vented Fuel Tank

[brainbug007]

I've nearly got my tank finished now and was wondering how people have vented theirs to comply with the IVA regs? I know some filler caps say they're vented like http://www.cbsonline.co.uk/product/8...ted***_ AEROV but I was wondering if there where other options to vent the tank? Also is there some sort of regulation to have an unleaded insert in the filler neck like http://www.cbsonline.co.uk/product/C..._Insert_LWFCIN as the product description seems to indicate?