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.