Replacement particle filters for the Blueair Pro M air purifiers. Uniquely designed to resist clogging and promote peak filtration performance, HEPASilent technology brings high efficiency and longer lasting air flow to air purification. Includes 1 HEPASilent V-shaped polypropylene pleated filter for removing pollutants such as bacteria, viruses, pet dander, dust, and harmful particles down to 0.1 micron in size. Since polypropylene fibers are waterproof, Blueair purification systems do not require the use of chemical-based bacteriostats or mold inhibitors. Instead of absorbing the moisture in which bacteria thrive, polypropylene repels water and naturally prevents bacteria, mold and mildew from reproducing inside the filter. Replace filter every 6 months.