Fuel vapor emission control system for an engine

A fuel vapor emission control system for connection to an engine having a fuel tank so as to purge fuel vapor introduced thereto into the engine, the system comprising:

• primary and secondary adsorbing layers for temporarily adsorbing fuel vapor introduced thereto, the primary and the secondary layers being connected in series;
• fuel vapor introducing means for introducing fuel vapor, from the fuel tank, into the primary layer during an engine fuelling operation, and for introducing fuel vapor from the fuel tank into the engine bypassing the primary and the secondary layers when the engine is running;
• and
• air introducing means for introducing air into, in turn, the primary and the secondary layers so that the air passing therethrough desorbs fuel vapor therefrom, and then into the engine, together with the fuel vapor desorbed from the primary and the secondary layers, when the engine is running.