An air handler, also known as an HVAC air handler, is a device used in heating, ventilation, and air conditioning (HVAC) systems to regulate and circulate air as part of a heating, ventilation, and air conditioning system. Air handlers are typically housed in a metal cabinet and contain a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers. The air handler is connected to ductwork that distributes the conditioned air through the building and returns it to the air handler. The air handler is responsible for circulating the air throughout the building, controlling the temperature and humidity levels, and providing a comfortable environment for the occupants. The air handler also helps to reduce energy costs by using energy efficient components and controls. Air handlers are used in both residential and commercial buildings and can be used in a variety of applications, including cooling, heating, humidification, and ventilation.