•  The check valve (two-way) cannot be removed as it is built into the fuel tank.

•  Mainly consists of positive and negative pressure valves.

•  The valve moves in response to the difference in air pressure between the fuel tank side and the atmospheric side, thereby changing the path of airflow.

•  When the pressure in the fuel tank becomes negative due to fuel consumption or other factors, the air path opens, drawing atmospheric air into the fuel tank.