Combing 99.97% True HEPA performance with Odor Absorbing Carbon Pre-Filters, the Winix Replacement filter E provides protection against smoke, dust, pet dander, pollen, and other allergens as small as 0.3 microns. HEPA, which stands for High-Efficiency Particulate Arresting filter is recognized as the most effective method for removing contaminants and irritants from the air. For Winix FresHome P450.