Blueair 603 HepaSilent Air-Purification System Designed for large rooms up to 698 square feet Patented HEPASilent technology traps 99.97% of harmful particles down to 0.1 microns in size Worlds highest Clean Air Delivery Rate (CADR) of 450 cubic feet per minute, 5 air changes per hour SurroundAirTM technology takes in air through an area six times larger than the average air purifier Includes a magnetic filter timer to alert you when the filter needs changing