The device itself is wonderful. It holds a lot of water and lasts for over 24 hours. It is ionic, really quiet, and does it's job. I have had several of these, though, and ultimately, after many months of use, the top cover begins to not fit properly over the base. The problem becomes worse and worse until the device can no longer be used. I thought it was because I used hot water to wash it. But my current unit has not been washed in hot water, ever, and still has this problem. The company needs to figure out why this happens. It does not happen in the smaller model of the same device. Also, in this device, if water gets into the mechanism it will not work. This makes it challenging to rinse and keep clean. They should fix that problem as well. I would switch to another brand but I have not yet found an ionic diffuser of this size that I like.