The DELTA 50-875 3-Speed Air Filtration System with Remote surpasses other air filtration systems by offering high air flow with three air-cleaning settings--540 CFM, 730 CFM, and 1,200 CFM--to suit your unique projects. Capable of filtering the air in a 20-by-20-foot room 13 to 18 times an hour, it comes equipped with a remote control that allows you to program the time delay feature to shut-off the filtration system up to four hours later. A patented, easy-to-read dirty filter indicator offers a needle-point illustration of your filter state--when the needle dips into the red zone your filter needs cleaning. The high-performance air filter includes a three-pocket inner filter, a heavy-duty pleated outer filter, and an electrostatic pre-filter that work together to busily trap pollutant particles larger than one micron, allowing your lungs to finally breathe happy.