The evaperation canister is part of the emissions system on your cruck, or any car to be exact. There are two hoses going to your canister. One hose goes to the gas tank, the other to the engine. The one going to the gas tank recieves fuel vapors from the tank, this keeps fuel vapors out of our atmosphere. All these vapors come into the canister and the canister "soakes" them up like a sponge. Then the line to the engine takes those vapors and uses them as fuel and burns them.
So the job of the canister is to trap vapors and burn them, making sure no gas goes to waste nor into the atmosphere
Now your canister sounds like it may be cracked, or have a leak, thus causing the vacuum from the engine to pull air from outside the canister, rather than pull vapors from inside. It may be time to replace it, but check to make sure its the canister thats broken, rather than a simple vapor line.
Reasons why you should make sure to have a working vapor canister:
Keeps our earth clean, them EPA guys aint all that bad
You will have a strong fuel smell without it
You would have to switch to a different fuel sending unit without a vapor line exit
The unburnt fumes may ignite somewhere in your car, instead of be trapped