Polluted air first passes through Alen's replaceable Pre-Filter to capture large particles, extending the life of the filter. In the second layer, air moves through a True HEPA material that attracts and captures dust, pollen, pet dander, mold spores and other airborne pollutants. In the final layer, clean air passes through hundreds of cells filled with Alen's patented Molecular Conversion Powder where tough pet odors are destroyed at a molecular level, leaving the air smelling fresh and pure.