We have owned a Pure 211 Plus (non-auto) for years (in the bedroom), and love it. We recently purchased a Pure 211 Plus Auto for the living room. It is nearly silent while running on the lowest setting (which has been almost always, for us). Shortly after purchasing it, we had a minor toaster-oven smoke incident. I did not think the smoke reached the living room, but I noticed that the purifier ramped up to a higher speed for a few minutes before settling back down to low. We have owned at least two other brands of purifiers, and we recommend this one. (It can also be set manually to a different speed).