An air handler, also known as an air handling unit (AHU), is a key component of an HVAC system. It is responsible for circulating air throughout the building by drawing in outside air, filtering it, heating or cooling it, and then distributing it to the various rooms. The air handler contains a fan, a filter, a heat exchanger, and a blower motor. The fan draws in outside air and passes it through the filter to remove dust and other particles. The heat exchanger then heats or cools the air, depending on the desired temperature. Finally, the blower motor pushes the conditioned air through the ducts and into the various rooms.