Mesh Micron Conversion Chart | Universal Filters, inc.
Diameter of a white blood cell = 25 microns Naked-eye visibility threshold = 40 microns Pollen = 60 microns Diameter of a human hair, typical human = 70 microns Table salt = 100 microns Openings in window screen, typical screen = 1475 microns (or .058 inches) Distance needed for first down in football, "1st and ten" = 9,144,000 microns