There is only one catch with this. How long does it take to clean all the air in a room. I have fan driven filter unit but have given up using it because it is ineffective unless it is used for very long periods and even then I suspect that, with the room in use or the window open, the air polution can replenish at a faster rate than the cleaner can clean it. Therefore it is difficult to see how a cleaner with apparently only convection currents caused by its heater to draw in the air can be very effective.