The short answer: It depends on which unit you are running. If you are running the Aqua-6 or an Aqua-8, as long as there is plenty of ventilation, you can be in the room. But, it is a rare occurrence that someone will have an allergic reaction to ozone. Consult your physician or practitioner for more information. The Aqua-6 produces 120 mg/hour of ozone. The Aqua-6 produces ozonated water for washing fruits and vegetables, drinking, and bathing. Meanwhile, the A7K makes 7,000 mg/hour of ozone and will treat cigarette smoke, skunk smells, and pet odors. If you're running the A7K under no circumstances is it safe to be in the room. Do not leave a pet in the room, and remove all plants.Likewise, do not run an MP-3000 ozone generator or stronger in an occupied room.