Purchasing a room air cleaner can be confusing if you do not know what comparisons you should make among different models.  In general, you are going to have to decide if you want a unit that combats dirt and other allergens or one that filters toxic chemicals from the air.  This is because usually a room air cleaner is designed to battle one or the other, but not both.  You also are going to want to decide if you want to deal with filters or not when it comes to your Room Air Cleaner.  There are positive sides to both, you simply want to investigate to decide which will meet your needs the best.