AeraSense is a new technology with the accuracy and performance of a professional sensor. It senses particles smaller than PM2.5, removes up to 99.9% of viruses and aerosols from the air adapting automatically with real time feedback. When in Silent Mode, the Purifier turns down its fan speed and noise level to allow a comfortable night’s sleep. The numerical PM2.5 indicator and the 4-step color ring provides real time feedback of your indoor air quality. Both AQI and the light on the UI can be dimmed and/or turned off avoid light disturbance for consumers. The Philips Air Purifier has 3 automatic purification settings: a General mode, an extra-sensitive Allergen mode, and an extra-powerful bacteria and virus mode. You can choose your preferred mode to personalize and optimize your purification. Removes aerosols including those containing respiratory virus, from the air which passes through the filter.