Air handling unit is a device used to regulate and circulate air as part of a heating, ventilation and air conditioning (HVAC) system. It consist of blowing fans, heating and cooling coils, humidification unit, filter system, mixing box and dampers. Air handling units are connected to a duct system that distributes the conditioned air throughout the building and returns it back.

With air handling units, the temperature of the environment is automatically brought to the desired value thanks to the thermostats placed indoors. In winter, they automatically discharge the return air and use the fresh air in the outdoor environment when the temperature of the outside air is lower than the temperature of the mixture air with the help of economizers and outdoor ambient & mixing chamber sensors. This is called free cooling. Thus, significant energy savings are made.