The Evaporative Control Canister Filter is a charcoal filter that resides inside a storage device that traps fuel vapors from escaping into the atmosphere. The emissions control system transfers the fuel vapors from the sealed fuel tank to the evaporative control canister until the engine is able to use the extra fuel vapor. The system is required in order to detect evaporative fuel system leaks as small as 0.040 inch between the fuel filler cap and the evaporative control canister purge valve.