Automatic Filter Replacement Program - Join our Filter Replacement Program today and receive your Blueair HEPASilent particle filters delivered directly to you. It’s easy to do: just choose when you want to receive them and you can stop at any time! Plus enjoy Free Shipping on all your HEPASilent filters, always! Replacement particle filters for the Blueair Pro L 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 2 HEPASilent V-shaped polypropylene pleated filters 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. Available auto-replacement shipment intervals are 4, 6 or 8 months.