The Bionaire True HEPA 360 UV Air Purifier features one 360 filter with 3 layers of filtration. The first stage captures large particles like hair and dust in the pre-filter. In the second stage, small particles as small as 0.3 microns pass through the True HEPA filter, which removes up to 99.97% of airborne allergens from the air including smoke, mold spores, pet dander, pollen, dust mites, and bacteria. Finally, in the third stage, the carbon layer eliminates common household odors such as cooking fumes and pet odors. The UV light uses UV rays to significantly reduce the presence of bacteria on the filter. The optional ionizer helps to bind smaller particles which then form larger particles that are more easily captured.