In a system for controlling the loss of fuel vapor from a vehicle fuel tank, the fuel tank vents are connected to the upper portion of a canister containing a quantity of fuel vapor adsorbing carbon retained under compression therein. The upper portion of the canister is also connected to the induction system of the vehicle engine, the bottom of the canister being open to atmosphere so that air is drawn through the carbon and the fuel vapor purged during engine operation. The canister is molded from nylon, the top being formed so that vapor from the fuel tank is discharged into the mid-portion of the canister. The top and bottom of the canister include molded grids and filter pads to prevent loss of carbon from the canister, and in one embodiment a nylon screen additionally serves to prevent carbon loss from the bottom of the canister. The top of the canister may contain appropriate valve structure to control fuel tank pressure and vapor flow.