Protec Humidifier Cleaning Cartridge ProTec Humidifier Cleaning Cartridge offers a fast and simple humidifier cleaning solution. This flow-through cartridge contains a gentle, patented and proven material, Aquastat. Small in size, you can easily drop this cartridge in the humidifier water tank and leave it there for 30 days for a fresh and sanitized water tank. It should be replaced once a month during use. This non-toxic cartridge works in all humidifiers. Why You"ll Love It: Get a clean, fresh and healthy humidifier without harmful chemicals. Features Contains no harmful chemicals All natural Offers fresh, clean mist Proven effective in clinical studies Non-toxic Concentrated cartridge Works in all humidifiers