GB/T 39193-2020 "Ambient Air—Determination of Particulate Matter Mass Concentration—Gravimetric Method": This standard, which came into effect on May 1, 2021, specifies the method for determining the mass concentration of particulate matter in ambient air through filter membrane sampling and weighing. The content covers principles, instruments and equipment, sampling and weighing procedures, result calculation and presentation, as well as the assessment of measurement uncertainty, quality control, and assurance requirements. It is applicable to measuring the mass concentration of ambient air particulate matter via filter membrane weighing, providing a standardized technical basis for the detection of ambient air particulate matter.