This was our third Blueair purchase and we have been very pleased with it thus-far. Our first two air purifiers was a larger model for our living room and my wife's shared office. They are great for the larger spaces. We tried using it in our bedroom and it was noticeable loud at night on the middle setting. I am a light sleeper though. We purchased the 311 auto and it has been great. You can't even tell it is running sometimes. The 311 auto has multiple settings and we are very pleased with it. Our house tends to be a bit dusty, also with the dog, and with two in the house we feel much more comfortable about the air quality.  I would recommend these model for anyone wanting a air purifier in there office or bedroom.