This diffuser uses ultrasonic technology with water and fills the air with a very fine mist. If has a large tank so it can be run for hours, but we only recommend prolonged use in unoccupied spaces. For inhalation purposes, use should be intermittent and staggered throughout the day. Diffusers can be used for aesthetic purposes or for disinfecting rooms. They can also be used to inhibit mold growth, but this requires prolonged use so it is better not to stay in the room(s) being treated since essential oils are very concentrated and can be intense. They are safe when exposure is limited to 5-10 minutes at a time when sitting at a distance of 3-6 feet from the diffuser.