Hard water is defined by its dissolved mineral content, mostly comprised of magnesium and calcium. It is a common issue, with 85% of the water in the U.S. is classified as hard water. While hard water does not necessarily pose any health risk, it is definitely harmful for appliances exposed to the mineral elements and can be frustrating to handle. Repeated exposure to hard water can cause an off-white scale build-up in appliances and pipes that ultimately decrease their effectiveness and can shorten their useful life. A demineralization filter is a great way to prevent the "white dust" and lime scale residue that results from hard water. The added benefit of using a demineralization filter is it provides protection and can extend the life of your Crane Adorable Humidifier. The Crane HS-1932 Animal Filter is compatible with all the Crane Adorable Animal Humidifiers.