To begin with, the EVAP system is responsible for keeping the fuel vapor from escaping into the atmosphere. Some of the parts of the system include the EVAP canister, fuel tank pressure sensor, fuel vapor vent valve, canister vent solenoid, fuel filler pipe check valve, canister purge valve and EVAP dust separator. The canister stores fuel vapors while the pressure sensor monitors tank pressure. The vent valve prevents overfilling and solenoid controls vapor flow. The check valve blocks fuel escape during refuelings. The purge valve regulates vapour flow to intake manifold. Dust separator prevents entry of particles into the system. Common symptoms include poor engine performance and gas smells in particular cases concerning EVAP faults. Inspection and component replacement may be necessary after a professional diagnosis using an OBD-II scan tool.