Evaporative Emission (EVAP) Canister
WARNING: This page is about a different car, the 2003 Mazda Tribute. However, it is still accessible from the selected car via links, so may be relevant.
Fuel vapors from the fuel tank are stored in the EVAP canister. When the engine is running, the vapors are purged from the EVAP canister for combustion. OBD II vehicles sometimes use multiple canisters, which is dependent upon the size and number of the fuel tanks used on a specific vehicle.