We love Blueair products - they are incredibly reliable, efficient, and most importantly, they work. The 511 is no exception. The idea is simple - big fan on top of a couple layers of filters - sucks in the air from the bottom and expels it out the top clean. The outer filter is easy to clean, and there are other colors you can purchase to match your decor. At the lowest speed, it is very quiet. Even at the highest, it is not any louder than a standing fan. Only wish it had wi-fi controls...