The ViraTech Air Purification Replacement Cartridge for the UV-400 is designed specifically for use in the UV-400 Air Purification System. The UV-400 automatically shuts down after approximately 8,800 hours (approximately 1 full year) of use, and will not operate until the cartridge has been replaced. The ViraTech Air Purification Replacement Cartridge for the UV-400 contains the patented ViraTech air purification technology that makes the UV-400 run. It kills greater than 99% of bacteria and reduces concentrations of odors and volatile organic compounds. Please note: UV-400 will supply a return shipping label so you can send the used cartridge back free of charge for proper disposal. The shipping label will come with the purchased ViraTech Air Purification Cartridge for the UV-400 and you can use the new box for the used cartridge’s return.