This air purifier was surprisingly strong for my bedroom and most importantly -- QUIET.  The motor adjusts itself all day long based on the air quality which is why I don't notice it during the evenings while I sleep.  I leave the machine on all day without any issues.  It doesn't take up a lot of space and sits on the foot of my desk -- after two weeks of use I notice that those annoying dust bunnies don't build up underneath my desk anymore which is awesome!