An evaporative cooler (also swamp cooler, desert cooler and wet air cooler) is a device that cools air through the evaporation of water. Evaporative cooling differs from typical air conditioning systems which use vapor-compression or absorption refrigeration cycles.
Evaporative coolers lower indoor temperatures by combining the natural cooling properties of evaporating water with an efficient air moving system. This combination of moisture and a steady breeze can lower indoor temperatures by as much as 30°F. Airflow is controlled by opening windows to allow the unit to push warm air outside. Evaporative coolers also add moisture, which helps keep fabrics and wood from drying out, and the water-filled pads act as a type of filter, removing dust and allergens from the air.
Evaporative coolers fall into several different categories:
Portable Coolers: cool small spaces or rooms, usually up to 300 square feet.
Mobile Coolers: cool much larger, open spaces like warehouses or garages, and can be used out-of-doors on patios or on job sites.
Window or Through-the-Wall: units cool one room, an entire house or a garage.
Down Discharge: coolers are installed on the roof, discharging the cooled air downward into the structure and are designed to cool an entire home.
Side Discharge: units are normally installed on the side of the building directly into the attic area, but can be installed on the roof, using an elbow to direct the airflow through an opening in the roof. They can cool an entire house.