We now own 2 units.  One was for the bedroom where my old labradoodle usually spent her day.  It worked so well we bought the larger unit for the main living area.  I am fascinated by how it senses when to turn itself on when there are cooking or bathroom smells.   We are very happy with this purchase.  An added bonus is a decrease in dust.  I hate to dust and now I don't need to as often.