The filtration efficiency of N95 respirator for particles with aerodynamic diameter of 0.075 μ m ± 0.02 μ m is over 95%. The aerodynamic diameter of air bacteria and fungal spores mainly varied between 0.7-10 μ m, which was also within the protection range of N95 respirator. Therefore, N95 respirator can be used for respiratory protection of some particles, such as dust generated in the process of grinding, cleaning and handling minerals, flour and some other materials. It can also be used for liquid or non oil particles that do not produce harmful volatile gases due to spraying. It can effectively filter and purify the abnormal smell inhaled (except toxic gas), help reduce the exposure level of some inhalable microbial particles (such as mold, anthrax, tuberculosis, etc.), but it does not eliminate the risk of contact infection, disease or death