Air Conditioner - Carry-Cool / Porta-Cool Vent Door

On older model air conditioners, the vent door is closed when the VENT button is out and to the left.  In this position, only the air inside the room can be circulated and conditioned.  Pushing the VENT button in and sliding it to the right opens the vent door, allowing a small amount of indoor air to be exhausted from the room.