Room air conditioners extract heat and moisture from the room air, cool and dehumidify it, and return the air to the room. A blower pulls warm room air through a filter. The main difference is that they are a single, self-contained unit with an evaporator or cooling coils, a condenser, and refrigerant-filled tubing all in one box. Air conditioner units mount in a window or through an opening in a wall since they need to expel hot air.