Heating . Ventilation and Air Conditioning ( HVAC ) is the technology of indoor and vehicular environmental comfort . Its goal is to provide thermal comfort and acceptable indoor air quality . HVAC system design is a subdiscipline of mechanical engineering , based on the principles of thermodynamics , fluid mechanics , and heat transfer . Refrigeration is sometimes added to the field’s abbreviation as HVAC & R or HVACR .
or ventilating is dropped as in HACR ( such as the designation of HACR – rated circuit breakers ) .