Pre-Filter Removes big dust contained in the air, hairs, big size dust and fiber dust. Nano-Silver Anti-Bacteria Sheet & Filter Remove must, virus, micro dust (over than 0.5um), normal bacteria with very powerful anti-bacteria resin and helps to protect the HEPA filter. HEPA Remove more than 99.97% of contaminated dust such as home dust, ticks, viruses, fungi, etc. which are bigger than 0.01um and including bacteria if remained from LDA filtering process.