The Delta 50-875 is a 3-Speed Ambient Air Cleaner. This 3-speed ambient air cleaner with patented Air Flow Indicator helps the user determine when its time to clean the filters. The dual filter system traps up to 99% of particles 1 micron in size. The blower provides 540, 730 or 1200 CFM, that filters the air in a 20 ft. by 20 ft. room between 13 and 18 times per hour. It includes a remote control for easy speed adjustment and timer settings. The time delay shut off can be set for up to 7-1/2 hours in 1/2 hour increments. The filter system consists of a 3-pocket inner filter and a pleated outer filter.