Bought my first one three years ago. After two years of continuous use it started getting noisy. I pulled off the back cover, added some Tri-Flow oil to the motor shaft and noise went away. One year later it is finally wearing out. Bought a brand new one from SMARTHOME. It works better than any of the seven different types I have tried in the past. Wake up each day without clogged sinuses. I have recommended this unit to three other people and they all love this particular air cleaner. IT WORKS GREAT? Most important, there is none of that ozone which I have found I am allergic to and get headaches and sore throats using. Another great point, the replacement filters cost much less than any other HEPA filter on the market that I have looked at.