The definition of an AHU, or Air Handling Unit, is a device used in heating, ventilation, and air conditioning (HVAC) systems to regulate and circulate air as part of a building’s climate control system. An AHU is a large metal box containing a fan and one or more coils. The fan draws air from the building into the AHU, where it is either heated or cooled, depending on the season, before being circulated back into the building. The coils are filled with either hot or cold refrigerant, depending on the desired temperature, and the fan helps to circulate the air. An AHU is an essential component of any HVAC system, as it helps to maintain a comfortable and healthy environment in a building. It is important to regularly maintain and inspect an AHU to ensure it is working properly and efficiently.