Abstract: A canister assembly is mounted between a fuel tank and an internal combustion engine. The canister assembly includes a canister holding a carbon charge for adsorbing fuel vapors emanating from the fuel tank. A trap box defines a plenum and is mounted on the canister and a canister pipe stub permits the plenum to communicate with the carbon charge. The trap box has a load port disposed thereon and the load port is connectable to the fuel tank for passing a flow of fuel vapors from the tank into the plenum with the fuel vapors becoming adsorbed by the carbon charge as the vapors flow from the plenum and through the canister pipe stub and into the carbon charge in response to an overpressure in the fuel tank. The canister pipe stub is arranged in the plenum so as to permit any liquid fuel accompanying the vapor flow to become trapped in the plenum thereby preventing the liquid fuel from reaching the carbon charge and causing the latter to become degraded thereby.