Looking for an education in fuel tank venting

The tank has to be vented; one way or another. There are several reasons for this.
1) As the engine consumes fuel, the pump pulls fresh fuel from the tank. If its not vented, the tank will soon collapse, from the lack of fresh air coming in to replace the fuel going out.Its also possible for the pump to not be able to pull fuel at all, or to pull fuel that is full of bubbles.
2) On an unvented tank; on hot days the vapor pressure in there can build pretty high, sometimes high enough to greatly distort the tank, and definitely enough to be a fire hazard to the poor sob who wants to refill the tank. And in certain situations the pressure can overpower the float valve and flood the engine and oilpan, and at least 1 or 2 cylinders.This could lead to engine destruction, however improbable.

The tank can be vented to atmosphere. There are at least 2 problems with this.
1)Gasoline is made up of several constituents, of varying degrees of volatility.The first to evaporate are the ones that make your engine easy to start.
2)Gasoline costs money.

The better idea is to outfit your car with a vapor canister system, which will store the evaporating fuel for you, and reintroduce it to the engine when circumstances are right.This system will take care of the venting issue, provided that it is correctly set up.It weighs in the neighborhood of 6 to 10 pounds, Ima guessing.