In the following HVAC system diagram, we have a mixing box, dehumidification unit, controlled zone, cooling coil unit, heating coil unit, extract fan, damper, air handling unit, gas burner, exhaust, and more. It should be noted here that HVAC systems are milestones of building mechanical systems that provide thermal comfort for occupants accompanied by indoor air quality. According to multiple zones, locations, and distribution, HVAC systems can be classified into central and local systems. Primary HVAC equipment includes heating, ventilation, and cooling or air-conditioning equipment. Furthermore, local HVAC systems can be located inside a conditioned zone or adjacent to it and have no requirement for ductwork. Local systems include local heating, local air-conditioning, local ventilation, and split systems.