An air handling unit (AHU), conditions and circulates air as part of a heating, ventilating, and air-conditioning (HVAC) system. A typical air handler is a large metal box containing a blower, heating andor cooling element, filter racks or chambers, sound attenuators, and dampers. Air handlers connect to ductwork that distributes the conditioned air throughout the building and returns it to the AHU. AHUs can alternately be set up to discharge (supply) and admit (return) air directly to and from the space served without ductwork.