Phat Filters Organic 6" HEPA Air filterHEPA Filters Can Help Eliminate Dust, Smoke, Mold, Bacteria, Pollen & Other Harmful VOC's The tightly woven synthetic HEPA fibers in this filter will help prevent mold, bacteria, pollen, insects and plant pests from entering your growroom or greenhouse. The HEPA fibers block out most airborne particles down to . 3 microns in size. That is 300 times smaller than the diameter of a human hair. The filter is also washable for extended efficiency.