HVAC systems are composed of four main components: heating, ventilation, air conditioning, and controls. Heating is the process of providing warmth to a space, typically through the use of a furnace, heat pump, or boiler. Ventilation is the process of exchanging air between the interior and exterior of a building, typically through the use of fans and ductwork. Air conditioning is the process of cooling and dehumidifying the air, typically through the use of an air conditioner. Finally, controls are the devices used to regulate the operation of the HVAC system, such as thermostats, dampers, and zoning systems. Together, these four components work together to provide a comfortable and safe indoor environment.