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The H2EO diffuser is a popular model. It is a functional looking unit–not unlike a humidifier, but does the job well. The unit uses distilled water and 5-10 drops of essential oil. Ultrasonic waves break the water and oil into a fine mist (3-5 microns) and no heat is generated in the process. These units run quieter than nebulizers, but the mist is not as concentrated. Like a nebulizer, you should not use any essential oils that have been cut with carrier oils (e.g. jojoba, almond, etc.).
This unit has 3 different settings, low, medium and high, and you can also set it to run for different lengths of time. There are five different preset modes that include continuous diffusion and intermittent diffusion options (i.e. cycles on and off). The tank holds about 8 oz. of water and the unit will shut itself off when the water runs low. The unit should be wiped out weekly with a cloth and a little alcohol, and the manufacturer recommends occasionally running some water and a little mild detergent through it.
This diffuser is moderately priced. It is a solid machine with some nice timer options. You also get a machine that is simpler to clean than a nebulizer. What you don’t get is style or fashion (unless you count the colored lights on the unit!)
Pros: fine mist of oil, adds humidity to the air, easy to clean
Cons: moderately expensive