- Ultrasonic cool-mist diffusion - Coverage: 538 sq. ft. (50 sq. meters) - Easy to use and clean - Auto shut off, choose between 1 or 4 hour run timesEssential Oil Diffuser AROMATHERAPY mist The Aura Cacia® Essential Oil Diffuser brings aromatherapy into your everyday space. Its simple modern design works well in any room. An alternative to synthetic air fresheners, it utilizes ultrasonic vibrations to disperse a fine essential oil and water cool-mist. By not using heat, the natural aroma profile of essential oils is protected.