The Blueair 400 Series Particle Filter utilizes HEPASilent technology to remove harmful particles from the air, such as pollen, dust, pet hair, and bacteria. Through electrostatic and mechanical filtration, Blueair air purifiers filter indoor pollutants with an accuracy of 99.97% for particles as small as 0.1 microns. The thermally bonded filter fibers made from polypropylene and polyethylene are naturally chemical-free, antibacterial, and resistant to fiber loss. The gradient filter structure is less dense than other filters, allowing Blueair air purifiers to achieve greater air circulation at lower air pressure and a quieter, more efficient release of clean air. The replacement filter for the Blueair 400 Series Particle Filter is made from 100% recyclable materials, ensuring that you only return clean air to your environment. Recommended filter replacement: every 6 months with 24 hours of use per day.