Breathe clean, refreshing air using the HEPA 240 Air Purifier. It features continuous smart monitoring so its Real Time Air Quality Indicator lets you know the current air quality level. Using a 4-In-1 True HEPA Filter, the air purifier removes 99 percent of bacteria in one hour, 99 percent of 2.5 micron particulate matter in one hour and 95 percent of formaldehyde in four hours. When in Auto Wind Mode, the fan speed adjusts to low, medium, high or turbo according to air quality detected by the dust sensor. Convenient timer lets you run the device one hour, two hours, four hours or eight hours before the air purifier automatically shuts off. Air purifier operates silently.