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The Auracacia Aromatherapy Diffuser is a fan diffuser that works by evaporation of essential oils on a re-usable cartridge/pad. Aroma is propelled into the room by the fan, which also hastens evaporation. Advantages of this unit are that it provides a gentle aroma without heat. This means the essential oils properties are not altered (although the essential oil molecules may evaporate at different rates.
Like any difffuser based upon evaporation, scent will be strongest at first and then slowly diminish. Those wishing a gentle, continuous aroma may want to consider an ultrasonic diffuser. As noted, the cartridge which holds the oil is re-usable, and contains segments so that you can use the same cartridge for different oils. It only requires a drop or two per use according the the manufacturer, meaning your bottle of essential oil will last a long time. It does come with a 1/2 oz. bottle of oil to get your started.
Pros: cartridge pad has different segments, no heat
Cons: low aroma coverage, expensive for a passive device, uneven evaporation