Five kinds of respirators were selected to analyze the protective performance of four kinds of atmospheric particulate matter in the real environment of Beijing with different pollution levels, and the effects of particle, respirator types, inspiratory flow rate and atmospheric PM_2.5 concentration on the protective performance of respirators were studied. The results showed that the four factors had significant effects on the protective performance of the facemasks. The particle protective performance of facemasks increased with the increase of particle size. The protective performance of four types of KN95 or KN90 facemasks for actual atmospheric particles could reach 80%, while the protective performance of disposable medical surgical facemasks was far lower than the above four types. The inspiratory flow also significantly affected the protective performance of the facemask, possibly due to the difference in filter material performance and leakage rate at different flow rates. The influence of atmospheric PM_2.5 concentration on the protective performance of different facemasks was complex 

and there was not a simple correlation.