The difference between protective masks and medical masks lies in the different protective functions and different filtering effects. Ordinary protective masks are mainly for the prevention of haze and larger particles. Commonly used in industrial dust control, not for personal protection against infectious diseases. Medical masks are mainly for filtering smaller particles in the air, such as bacteria and viruses. It is suitable for use in medical environments to block droplets, blood, body fluids, secretions, etc. According to different levels of protection, they are divided into general medical masks, medical surgical masks, and N95 masks. Ordinary medical masks are mainly used in ordinary medical environments. It can block the pollutants sprayed from the mouth and nasal cavity. Medical surgical masks can filter ≥90% of 5μm particles. It is used to prevent the spread of blood, body fluids and splashes. Medical surgical masks are divided into three layers. The outer water-blocking layer blocks splashes; the middle filtering layer effectively blocks tiny particles; and the inner water-absorbing layer absorbs water vapor generated by the wearer’s breath. N95 masks can filter ≥95% of 0.3μm particles with better sealing. The number of mask layers is usually 4~6, the inner and outer layers have the same function as surgical masks, and the middle layer has different number of layers according to different brands, which is mainly used for filtration.