"This device is AMAZING. I've had 3 friends comment on it and ask where I got it from. The only issue I had with it, is that it beeps when it runs out of water & auto shuts off. It isn't a huge deal though because it can last for 12 hours, so what I do is make sure that it has enough water before I go to sleep and it runs all night. In the morning it'll still be running so the beep doesn't bug me at all. I use YL oils with this and it works wonderful."