A face mask is a kind of hygiene product, which is generally worn on the mouth and nose to filter the air entering the mouth and nose to block harmful gases, odors, droplets, viruses and other substances. It is made of gauze or paper and other materials. Face Masks have a certain filtering effect on the air entering the lungs. Wearing masks has a very good effect when working in a polluted environment such as dust when respiratory infectious diseases are prevalent. Masks can be divided into air filter masks and air supply masks. The dust blocking efficiency of the mask is based on its blocking efficiency against fine dust, especially respiratory dust below 2.5 microns. Because dust of this particle size can directly enter the alveoli, it has the greatest impact on human health. The dust blocking principle of gauze masks is mechanical filtration, that is, when the dust collides with the gauze, some large particles of dust are blocked in the sand cloth through layers of barriers. For some fine dust, especially dust smaller than 2.5 microns, it will pass through the mesh of the gauze and enter the respiratory system. Dust masks are composed of activated carbon fiber felt pads or non-woven fabrics, and those respirable dust smaller than 2.5 microns are blocked in the process of passing through this filter material, which plays the role of filtering air.http://www.yfdisposable.com/covid-19-ppe/face-mask/