This Blueair filter set 5210i/5240i ensures that your Blueair Blue 5210i/5240i air purifier operates perfectly. The filter set captures airborne pollutants down to 0.1 microns. The device includes a DustMagnet™ filter that effectively removes chemicals, hazardous organic compounds, and light household odors from the air. The unique HEPASilent filter, which combines electrostatic and mechanical techniques, kills germs and helps minimize airborne particles that can trigger allergy symptoms, including pollen, dust, mold spores, pet dander, viruses, bacteria, and fine smoke particles. It is recommended to replace the filter every 6 to 12 months, depending on indoor conditions. The filter replacement indicator lets you know when it's time to change the filter.