This article has focused on the functions and operation systems of the HVAC. A thorough analysis of each function of the HVAC system has been made, and it may be concluded that the operations carried out by the units make them indispensable for the use of thermal variation and comfort. HVAC systems are therefore widely used in today’s world in all spheres which require regulation of temperature and the need for optimal indoor air quality. Through its functions and efficiency, the HVAC system has rendered itself as a extremely valued and integral part of almost every concerned field of work.