We have two Alen BreatheSmart filters (Classic and Flex50) in our home. Our home office has become the focal point for my wife and I and our cats! My wife's allergies were driving her nuts in the office. We talked to Alen and selected the BreatheSmart Flex to add to the office. Within hours we could tell the air was cleaner and my wife's allergies have subsided appreciably. And the cats are still here! It is quiet and a great addition.