The Blueair Sense+ air purifier comes with Blueair's patented HEPASilentPlusTM technology, the world's most advanced and silent filter system. It's a revolutionary combination of mechanical and electrostatic filtration. Air is drawn into the air purifier where large airborne particles and gaseous pollutants are captured in the first filter cassette. The air continues through an ion chamber where particles not captured mechanically are charged with negative ions, so they get attracted and caught by oppositely charged fibers in the second filter cassette. The purified air, virtually contaminant-free, is then re-circu-lated into the room.