Evaporative coolers in residential applications save energy compared with conventional vapor-compression air conditioners. However, traditional evaporative units must move large quantities of air to achieve adequate cooling. Moving all that air generates a lot of noise and leads to the need to directly exhaust that air. In many cases, exhaust is accomplished simply by opening windows, which can introduce wind-borne dust and raise security concerns. A new 3-ton equivalent evaporative cooler called the OASys addresses these problems by using both direct and indirect evaporative cooling. This two-pronged approach produces a greater temperature drop, thereby reducing the volume of air required. The OASys also uses less energy than conventional evaporative coolers.