This means that if the room where the air purifier is located is exposed to certain air pollutants, the air will start to deteriorate as soon as you switch off the air purifier. Therefore, I recommend using the air purifier 24/7 or turning it off periodically if you think the air is clean enough. levoit… Continue reading Levoit LV-H132 True HEPA Air Purifier w Nightlight Sears Marketplace