In simple terms, HVAC systems manage the air you breathe indoors by keeping it at the right temperature and free from impurities. It works behind the scenes in homes, schools, offices, and even your favorite stores to make sure you're comfortable, no matter the weather outside. 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.