The four levels of protective masks have the highest limit: the maximum limit of PM2.5 concentration allowed by the A, B, C and D masks is 700 μg/ m³, 500 μg/ m³, 300 μg/ Cubic meters and 200 micrograms/ cubic meters. When the ambient air uses particulate matter as the main pollutant, after wearing a protective mask suitable for the air pollution environment, the concentration of fine particulate matter in the air taken into the body is reduced to meet the good ambient air quality (that is, the PM2.5 concentration value must not exceed 75 Μg/ m³) and above.

The new national standard has more stringent requirements for the intrinsic quality of masks. It has set color fastness, strength of the mask tape and the fracture strength at the connection between the mask tape and the mask body, formaldehyde indicators, pH indicators, decomposable carcinogenic aromatic amine dyes, and respiratory resistance. , Microorganisms, visual field, protective effect, residual ethylene oxide and other 10 main indicators. Among them, the formaldehyde index of the mask should be less than 20 mg/ kg, the pH value should be between 4.0 and 8.5, and no coliform bacteria and pathogenic pyogenic bacteria should be detected in the mask.