Heating, Ventilation & Air Conditioning (HVAC) is the use of various technologies to control the temperature, humidity and purity of the air in an indoor space. Its goal is to provide thermal comfort and acceptable indoor air quality. It is an important part of of residential structures such as single homes, apartment buildings, hotels, medium to large commercial & industrial buildings.Ventilation is the process of exchanging or replacing air in any space to provide high indoor quality which involves temperature control, oxygen replenishment, and removal of moisture, odours, 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. Methods for ventilating a building are divided into mechanical/forced and natural types