Humidifier Cleaning Balls: Suitable for almost all humidifiers, including the following types of household humidifiers and steam humidifiers: cold mist (impeller type), warm mist humidifiers, evaporative humidifiers, and steam humidifiers. Also suitable for aquariums. Removes mineral deposits: The cleaning ball helps prevent and reduce the white powdery residue caused by minerals in hard water. This hard water "powder" may contain calcium, , or magnesium. Purifies water: Reduces odors and harmful substances by up to 99%, keeps humidifier mist clean, and reduces the frequency of water tank cleaning. Easy to use: Simply place it in the water tank for a fresh, clean mist. It is recommended to replace the cleaning ball every 30 days. This product contains no irritating chemicals.