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The AromaShell Diffuser (manufactured by Hubmar) works through passive diffusion assisted by a gentle heat. This is a great alternative to an oil burner if you don’t want open flames (e.g. children or pets around). Operation is simple, you apply a few drops of straight essential oil to the stainless steel tray and turn the unit on. The oils will be gently warmed and evaporate into the room. Clean up is simple–once the tray has cooled simply wipe the tray out with a cloth.
The Aromashell is best used in smaller spaces as passive diffusion methods generally do not provide a strong nor long-lasting scent. This unit might be appropriate for a bedroom or office, but not a larger living area. Diffusers that work through evaporation all have the disadvantage of uneven evaporation: the most volatile components of the essential oil will evaporate first. This “separation” of components may affect therapeutic properties of the essential oils, however if your primary goal is to scent your home naturally, this is not an issue. Read more about the pros and cons of passive diffusion.
Pros: No open flame, gentle aroma, easy cleanup, inexpensive
Cons: Small coverage area, uneven evaporation