AeraSense is a professional-grade sensor that accurately identifies fine particles that are even smaller than PM2.5 (including most common indoor airborne allergens). It then processes this information to ensure that the purifier’s settings are at the ideal level for current air conditions, and for continuous re-assurance. Then give you feedback of real time indoor air quality by showing PM2.5 level. Upgraded VitaShield technology effectively removes particles as small as 20 Nanometers* (more than 100 times smaller than upper limit of PM2.5), including common allergens, bacteria and some viruses. It also provides the assured protection from TVOC and odor. PM 2.5 is defined as fine dust particles of a diameter of 2.5 micrometers or less. PM 2.5 can penetrate and settle in the deepest areas of the lungs and cause health problems. The NanoProtect HEPA filter is designed for superior purification efficiency and lifetime against airborne particles. The ever-finer filter effectively removes 99.97% 0.3µm particles*, including common allergens, dust, pollutions, bacteria and some virus.