An air handler, or air handling unit (often abbreviated to AHU), is a device used to regulate and circulate air
as part of a heating, ventilating, and air-conditioning (HVAC) system. An air handler is usually a large metal
box containing a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers. Air handlers usually connect to a ductwork ventilation system that distributes the conditioned air through
the building and returns it to the AHU. Sometimes AHUs discharge (supply) and admit (return) air directly to and from the space served
without ductwork.