It is abbreviation for heating, ventilation, and air conditioning systems —the technology of indoor or automotive environmental comfort.

• Heating: In a vehicle heating stands for raising the temperature inside the vehicle using heat from the engine.
• Ventilating: It is the process of replacing air in vehicle space to control temperature or remove moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and to replenish oxygen. Ventilation includes both the exchange of air to the outside as well as circulation of air within the vehicle.
• Air Conditioning: It means removal of heat from the vehicle using a refrigerant.

HVAC consists of Heater, Evaporator & Blower Unit.