Model PC-1. Your humidifier stays cleaner, longer. Simply drop in tank for fresh, clean mist; Works in all humidifiers; Keeps cleaning for 3 days; Safe and non-toxic. Concentrated antimicrobial cartridge. Continuous protection against slimy build-up in humidifier. The Protec Cleaning Cartridge features a patented antimicrobial Aquastat, to continually inhibit the growth of odor-causing bacteria and mold in the cartridge as well as help prevent the buildup of slime in your humidifier. In addition the Protec Cartridge provides peace of mind that the mist is fresh and clean. Safe, non-toxic the Protec Cartridge uses the same antimicrobial that has been used for years in the food and drinking water industry to prevent the growth of odor-causing bacteria. The Protec Cleaning Cartridge is antimicrobially treated to help prevent the growth and migration of mold, fungus, algae and odor-causing bacteria on the cartridge.