Who knows?
This item was recommended to me by my brother-in-law who works in and around hospitals frequently, and is thus frequently sick. The problem is, there really is no objective way to tell if it works or not! I plugged it in by my bed, thinking that at least I would be breathing germ-free air while I slept. Trouble is, if it indeed does what it says it does, I should have placed it by my roommate who was already sick, in order to kill the germs he was breathing out! I ended up catching a bad cold and feeling like I wasted my money. The thing is kinda loud, too, so if you have trouble falling asleep I wouldn't recommend it. At first the "white noise" aspect was okay, but after a while it just got irritating. I unplugged it and now it's just collecting dust.
Rating: 2 stars