... for a longtime, then we open the door and come in the room, you will feel bad, smell foul air ... gets the flu. Because they are weak, and stay in a same classroom for longtime, it’s easy to ... be Cross-infection. If you use ozone when nobody in the room to kill flu and bacteria, refresh the ... clean.Office roomHotelHospitalCellarPublic place, such as, Public Toilet What is Ozone? Company Information: