HEPA (High-Efficiency Particulate Air) Filters are designed to remove 99.97% of all particles down to 0.3 microns in size. (Pollen size= 5-100 microns & human hair= 70-100 microns.) The American Lung Association claims they "are the most efficient mechanical filters for removing small particles which can be breathed deep into the lungs. The highest efficiency air cleaners.