An AHU is a device used to filter, condition, and circulate air as part of an HVAC equipment. The AHU system includes a large insulated metal box, which comprises a fan, heating and cooling elements, sound attenuators, filter racks, and dampers. Air handlers are connected to a duct work system through which conditioned air is distributed across a building and is returned back to the air handler. It caters to various needs such as heating, cooling, or both depending on the specific duty and weather conditions. Capacity, size, and complexity of AHU system vary considerably depending on the job they are designed to perform. The system is used in both residential buildings and commercial set ups.