DESC: AllerAir's air purifier features a complex filtration system made from quality materials to ensure that the air surrounding you is breathable. The 4000DExec model is specially designed to remove heavy concentrations of pollutants from small areas. An accessible pre-filter on the bottom makes this air purifier low-maintenance. Micro-HEPALaboratory tested HEPA (high efficiency particulate air) removes 99% of particles .1 microns in size, leaving ambient air pristine.Heavy Duty FilterThe large 16 lb. carbon filter works with the pre-filter to eliminate carbon from the air. Ultra-Mobile Four pivoting wheels and a sleek, cylindrical design makes 4000DExec air purifiers unobtrusive in any space. Adjustable Filtering HEPA air purifier has three speeds to adjust air flow through the air purifier: low, high, and turbo so you can adjust circulation.