The best made better! The 601 cleans more air more efficiently. In rooms as large as 679 square feet our patented two-stage HEPASilent technology captures 99.97% of 0.1 micron particles including allergy-provoking pollen grains dust mites mold spores and pet dander particles.Blueair is the system for people living with allergies asthma or other respiratory conditions or for anyone who wants cleaner more breathable air. Advances in fan and filter design have dramatically improved efficiency gaining the new 601 even better Clean Air Delivery Rates than the original Best of Class 501.Value-added features include quiet operation low energy use steel construction and easy maintenance: simply open the units lid lift out used filters and drop in Replacement Kit every 6 months.