3M mask includes thermal mask, particle proof mask and medical mask. Among them, the medical mask meeting the requirements of N95 level or above can prevent the virus from entering the human body easily from the respiratory tract, but 3M comfortable thermal mask can't prevent the virus, only has the function of keeping warm and resisting cold. China national standard gb2626-2006 has three filtration efficiency levels, namely 90%, 95%, 99.97%. 95% is applicable to smoke, highly toxic dust and pathogenic microorganisms, such as influenza virus. The higher the protection level of respirator, the better the filtration effect. It should be noted that N95 is the detection standard of the United States; Kn90 and kn95 are the protection standards of China; FFP2 and ffp3 are the European protection standards, and the protection effect is ffp3 > FFP2 = N95 = kn95 > Kn90.