Blueair HEPASilent particle filter is the ideal choice for allergy and asthma sufferers as well as other health-conscious individuals that need high-efficiency particle removal. Patented HEPASilent filter technology generally provides higher filtration performance than other air purifiers, trapping up to six times more dirt. Fine polypropylene fibers effectively capture 99.97% of airborne particles. The Blueair 3-stage progressive filter effectively removes every type of particulate air pollutant including allergens, pollen, mold spores, dust, pet dander, bacteria, and viruses. Compatible with Blueair model 23.