The OZONOS AC-I can be used around the clock. For the AC-I PLUS and AC-I PRO models, we must advise you to leave the room after 8 hours at the latest. In principle, however, you can rely on your senses when using the OZONOS: If you can smell the ozone, this means that there are no more substances in the air with which it can react. The room is clean and the OZONOS can be switched off.