Philips NanoProtect 600i Series HEPA FilterThe 2 layer filtration of NanoProtect HEPA and pre filter ensures that you are protected from PM2. 5, bacteria, pollen, dust, pet dander and other pollutants. HEPA filtrationOur 2 layer filtration system featuring NanoProtect HEPA technology captures an impressive 99. 97% of ultra fine particles as small as 0. 003 microns1 NanoProtect HEPA technology not only traps pollutants, but also uses an electrostatic charge to attract them, cleaning up to 2x