EVAP Canister
Evaporative Emissions canister—a plastic container filled with activated charcoal that traps and stores fuel vapors from the gas tank to prevent air pollution.
The EVAP canister (often called a charcoal canister) is a core component of the vehicle's Evaporative Emission Control (EVAP) system. Its primary role is to prevent harmful gasoline vapors from escaping the fuel tank and venting into the atmosphere. The canister is filled with highly porous activated charcoal pellets that act as a sponge, absorbing and holding fuel vapors when the engine is turned off.
When the engine is running under normal driving conditions, the engine computer opens the purge valve, allowing engine vacuum to draw fresh air through the canister, pulling the stored fuel vapors into the intake manifold to be burned cleanly in the cylinders.
Common issues include charcoal decay, physical cracking, or liquid fuel flooding the canister due to "topping off" the gas tank. A faulty canister will trigger a check engine light and prevent the vehicle from passing emissions testing.