The Pure Guardian Humidifier Demineralization Cartridge works with Pure Guardian Humidifier models H1100 and H1300 Model Series, and H7500 and H7550 Models. The Pure Guardian Humidifier Demineralization Cartridge dematerializes the water in your humidifier which helps prevent the release of minerals into the air which cause the build-up of white dust over lengthy periods of use. Use of the Pure Guardian Demineralization Cartridge can extend the life of a humidifier, making it a great and affordable option. The cartridge assembles quickly and easily into the existing lid of the humidifier tank and removes dust and minerals to help ensure these particles do not get misted into the air. To attach your new Pure Guardian Demineralization Cartridge, simply remove the lid from your humidifier tank and screw the cartridge onto it before replacing the lid. That's it, for best results, the Pure Guardian Demineralization Cartridge should be changed about once every 3 months or every 1000 hours or 260-Gal. of water, although hard water areas may require that the Demineralization Cartridge be changed sooner. Color: Whites.