Don't place it in any type of enclosure as that may lead to overheating. Get it off the floor if you can as that puts it nearer the major source of dust. If you can't manage that the best thing to do is to take the side off every three to four months and clean the dust out. I use an Air Duster Spray click here. Just very short bursts of the spray will get the dust out and leave for ten minutes or so afterwards as compressed air can sometimes be slightly damp.