The Yankee Candle ultrasonic diffuser with relaxing light to diffuse essential fragrance oils will create a fragrant oasis of calm in your home, especially where you can't have a lit candle - so it's a safe way to smell. Choose the scent and color of the light and then just relax! The diffuser uses water and Yankee Candle fragrance oils. Just 5-7 drops of oil and you will scent the room continuously for up to 4 hours.