Expensive but I use JWR Germicidal Air Systems. They work very well but are a expensive to acquire and maintain. But they are well with it with surgical UV bulbs. I learned of them from a woman with more than 100 birds in her house, and she kept up with them well! I also know of a rescue with 49 birds, 30 of which are dusty cockatoos. You can find their ad in BirdTalk magazine.
