This is the HEPASilent SmokeStop replacement filter for all air purifiers in the Blueair 400 Series, such as the 401, 402, 403 and 450E.
The Blueair 400 Series SmokeStop filter uses Blueair’s patented HEPASilent technology. This filtration technology is a combination of mechanical and electrostatic filtration, and allows the Blueair 400 Series air purifiers to deliver more clean air at a faster rate with less noise.

The Blueair 400 Series SmokeStop filter is a Three-Stage Progressive Filter – a filter that resembles having many filters in one.
The filter is made up out of three different levels of millions of ultra thin fibers, and with its ‘lock-in’ design, once captured the particles are not re-released back into your environment, even when the filter is heavily loaded.
The first layers capture larger particles like pollen and dust, and the later layers capture smaller particles like bacteria and exhaust particles.
Regular filters are thinner and mostly consist of the same fiber size and material throughout, this leads to them clogging up sooner. However, the unique design of the Blueair 400 Series Three-Stage Progressive Filter resists clogging, and allows the Blueair 400 Series air purifiers to perform longer on their peak performance.
The 400 Series SmokeStop Filter includes 0.9kg of activated carbon for odour and gas filtration. This removes gaseous pollutants such as cigarette and cigar smoke, or other VOCs (Volatile Organic Compounds) such as household paints.