Evaporative Emissions Control 

Help the environment and don't spill your gas
Oh wait, your car does something like that for you
​Check it out
  1. evap system picture

Interactive Tool

Fuel Tank
Gas will evaporate especially at elevated temperatures in the gas tank. The vapors can overpressurize the tank and need purged. Where best to put the vapors than into the engine to burn.
Vent Valve
Throttle Body
Purge Valve
Charcoal
Canister
Charcoal is there to hold the vapors until the throttle body calls for them, like when the gas pedal is pressed.
Charcoal Canister
Under the Hood
Valves
The vent valve allows air to be sucked in and by a vacuum pull the fuel vapors through the purge valve and into the throttle body.
Under the Cabin
Under the Trunk
Throttle Body
The throttle body has a small hole in it to allow for the air/fuel vapors to enter. When the throttle body butterfly valve opens a small orifice opens on the throttle body housing which allows vapors to pass into the oncoming air stream.
Gas  Cap
Gas Vapors
Fuel Tank
Liquid Gas

Various Evaporative Emissions Pictures

  1. evap system
  2. evap system
  3. evap system
  4. evap system