Evaporative Emission Control System is the fuel tank ventilation.

The EEC of the English Evaporative Emission Control System – Control ventilation system. The system controls evaporation from the fuel tank to prevent leakage of dangerous hydrocarbons into the atmosphere. Prevents, inter alia, the risk of explosion.

Source: http://www.glo­baldensoproduc­ts.com

Especially in the summer months with fuel in the tank evaporates. Container with activated charcoal absorbs temporarily odpařující the hydrocarbons from the fuel. When the engine is running and the check valve is open, liquefied fuel is přisáváno return pipes to the cylinder along with air and burned.