HVAC is the technology of indoor and vehicular environmental comfort. The purpose is to provide thermal comfort and sufficient indoor air quality. HVAC is an acronym that stands for (Heating, Ventilating, and Air Conditioning). A HVAC system design is based on the principles of thermodynamics, fluid mechanics and heat transfer. The three main functions of heating, ventilation and air-conditioning are interrelated, especially with the need to supply thermal comfort and acceptable indoor air quality within reasonable installation.