Different exposure risk groups can be divided into 5 levels: 1, high risk: clinicians, nurses, etc. in medical institutions in infected areas, preferred medical protective masks, the second choice in line with N95/KN95 and above standards of particulate protection masks. 2, higher risk: emergency work medical staff, etc., can wear a particulate protection mask in line with N95/KN95 and above standards. 3, medium risk: general outpatient, ward work health care workers, can wear medical surgical mask. 4, lower risk: supermarkets and other crowded areas of the public, can wear disposable medical masks. 5, low risk: home indoor activities, diaspora residents, etc., may not wear masks.