The dust blocking efficiency of the mask is based on its blocking efficiency for fine dust, especially for respirable dust below 2.5 microns. Because dust of this size can directly enter the alveoli, it has the greatest impact on human health. The principle of dust blocking of gauze masks is mechanical filtration, that is, when dust hits the gauze, it passes through layers of barriers, blocking some large particles of dust in the sand cloth. For some fine dust, especially dust less than 2.5 microns, it will pass through the mesh of the gauze and enter the respiratory system. Dust-proof masks are composed of activated carbon fiber mats or non-woven fabrics as filter materials. Respirable dust less than 2.5 microns is blocked during the process of passing through this filter material to filter the air.