The Winix 5520 features a 4-stage air purification system, this unit removes 99.99% of airborne particles as small as 0.01 microns in size. Winix’s PlasmaWave® Technology may help to reduce the presence of airborne pollutants and impurities. The unit’s built-in Smart Sensors detect and monitor the quality of air in your environment and provides a visual representation of your current air quality. When in Auto Mode, the unit automatically adjusts fan speeds to ensure efficient and cost-effective cleaning. Sleep mode is automatically activated when the room is darkened, providing quiet, energy-efficient operation.