Heating , ventilation and air conditioning ( HVAC ) [1] 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 ).
HVAC is an important part of residential structures such as single family homes, apartment
buildings, hotels and senior living facilities, medium to large industrial and office buildings such as
skyscrapers and hospitals, onboard vessels , and in marine environments, where safe and healthy
building conditions are regulated with respect to temperature and humidity, using fresh air from
outdoors.
Ventilating or ventilation (the V in HVAC) is the process of exchanging or replacing air in any space
to provide high indoor air quality which involves temperature control, oxygen replenishment, and
removal of moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and other gases.
Ventilation removes unpleasant smells and excessive moisture, introduces outside air, keeps interior
building air circulating, and prevents stagnation of the interior air.
Ventilation includes both the exchange of air to the outside as well as circulation of air within the
building. It is one of the most important factors for maintaining acceptable indoor air quality in
buildings. Methods for ventilating a building may be divided into mechanical/forced and natural
types.