I purchased this unit for my mom for Xmas for her bedroom (approx 368 sq ft) and she loves it. My stepdad has allergies and recently underwent surgery for colon cancer, so he's confined to the bedroom, and they said this purifier has totally removed the "stale" air. I had to get one for myself this past Sunday, and I LOVE IT! My hubby smokes cigars (my 5yr old hates it too, don't blame him!)and I put this in our Family room, when my son comes downstairs, not a word! when normally my son would have a mouthful to say about no smoking in the house! Its absolutley silent, you wouldn't even know its working until you smell the freshness of the air, it juts smells clean. A must have for anyone w/ lungs!