Why must a portable air conditioner have a hose?

Portable air conditioners need a vent hose to pull air and cool it before it is channeled to the room. Certain brands and units are equipped with two vent hoses; one hose draws air into the unit for cooling, while the other expels warm air from the room.

A portable air conditioner also has a drain hose. This collects the condensed moisture resulting from cooling the air. Depending on the model, the collected water is drained all the way out of the window, into a bucket or through an opening designed for the purpose. Fully self-evaporative models are advanced models that mechanically evaporate moisture through the exhaust hose along with hot air.