Comes standard with the Alen A350 and A375 Air Purifiers (Visit alencorp.com for details), the Alen HEPA-Fresh Filter combines three layers of filter technology to purify and freshen the air in your home. Polluted air first passes through Alen"s washable Pre-Filter to capture large particles, extending the life of the filter. In the second layer, air moves through a unique, electrostatically charged HEPA style material that attracts and captures dust, pollen, pet dander, mold spores and other airborne pollutants. In the final layer, clean air passes through a layer of Alen"s Activated Carbon, reducing light odors and chemicals commonly found in the air from cleaning products, smoke, cooking, pets and various other household materials. Instructions for Use ? Over time, the HEPA-Fresh Filter becomes overloaded with particles, decreasing its filtration performance. We recommend regular filter replacements, at least every 6 months with normal use. ? Rinse or lightly vacuum the removable black Alen Pre-Filter as soon as it develops a layer of visible particles. Allow it to completely dry before replacing. Washing or vacuuming the white HEPA style material will damage the fibers and is not recommended.