The masks we can buy now should be divided into three categories: N95 (including KN95), medical masks, and ordinary masks. 1, N95 (including KN95) masks: First of all, it is clear that N95 is the American standard and KN95 is the national standard. Features are able to filter 95% 0.3um particles and have a blocking effect on viruses. Used for airborne diseases. 2, disposable surgical medical masks: medical disposable masks are usually divided into three layers: the outer layer has a water barrier to prevent droplets from entering the inside of the mask; the middle layer has a filter layer that can block 90% of the 5μm particles; the inner layer near the mouth and nose is used to absorb moisture. 3.Ordinary masks: contain old-style cotton masks, activated carbon masks made for PM2.5 prevention, and sponge masks used for warmth in winter. They are useless against the new coronavirus! These masks usually only protect against haze, and are thick, stuffy and poorly fitted to the face. Q: If I need to wear a mask for protection, how should I choose a mask? A: Choice one: medical surgical masks. Need to follow the standards of medical-surgical masks. Nursing masks, cotton masks and sponge masks are not recommended. Choice two: N95 medical protective masks. Of the two types of anti-biological and haze, please choose anti-biological 1860 or 9132. Q: Is the mask effective to wear all the time? A:No matter what type of mask, the protection is limited and must be replaced regularly, preferably every 2 to 4 hours. Q: I wear a mask with fog on my glasses, what should I do? A:The correct way to wear a mask: wash your hands before wearing, be sure to fit your face, front and back correctly, form an airtight environment, and let the ventilation go through the mask instead of the gaps around it. Tips: How to handle medical masks after use in daily life? If the mask is wet or soiled with secretions, it must be replaced immediately. Discard the mask after use, discard the material used to cover the mouth or nose, and wash it properly (e.g., with plain soap or detergent and water) and perform hand hygiene after removing the mask.