My Protective Face Masks are made with 3 layers for the ultimate protection against airborne pathogens. The first outer layer is 100% Polyester Waterproof Material, the Charcoal insert between the first and second layer is a PM2.5 Grade Filter. The inner layer is made with fine weave cotton. PM2.5 Charcoal Filters are shown to be effective in blocking the vast majority of airborne particulates, even the very smallest nanoparticles. The PM2.5 name comes from these filters' original use as protection against Particulate Matter 2.5, the smallest and most dangerous form of air pollution.