When wearing a surgical mask to prevent the spread of viruses, the white side must face inward. Surgical masks are called medical surgical masks, which prevent the spread of viruses to a certain extent by blocking pathogenic microorganisms, body fluids and particles from being inhaled or exhaled directly by the body through the filter media. Medical surgical masks are divided into three layers, from the outside to the inside in order to waterproof layer, filter layer, absorbent layer. The outer layer (blue or green and other colored layer) is the waterproof layer, which is sanitary polypropylene imitation sticky cloth that can block splashing liquid; the middle layer is the filtration layer, which is efficient filtration meltblown cloth made of polypropylene spinneret, which can effectively block 90% of particles and germs with a diameter of 5μm; the inner layer (white) is the absorbent layer (comfort layer), which is sanitary polypropylene imitation sticky cloth. The inner layer (white) is an absorbent layer (comfort layer), which is a hygienic grade polypropylene imitation viscose fabric with a soft inner layer that fits the face and absorbs moisture and water released by the wearer. Therefore, when wearing a medical surgical mask, the colored side should face outward and the white side should face inward. If you wear it backwards, the water-absorbent layer will become a waterproof layer, and the waterproof layer will become an absorbent layer, which will cause saliva to cling to the surface of the mask and accumulate more and more, which may wet the mask and make it lose its filtering function, and it will not be able to play the role of preventing the spread of viruses.