The Vornado AC350 Whole Room Air Purifier uses true HEPA filtration, the most effective filtration available, to remove up to 99.97% of airborne allergens down to 0.3 micron in size. The Vornado Whole Room Purifier actively circulates and filters all the air throughout a room. Without powerful circulation, the air cleaner is only cleaning the immediate area around the unit. The AC350 uses a radial blower to intake and clean all the air in the room- up to 220 sq. ft. Precision engineering allows the blower to operate quietly, despite its powerful air flow.