This part of ISO 21438 specifies a method for the determination of the time-weighted average mass concentration of sulfuric acid and phosphoric acid in workplace air by ion chromatography. The method is applicable to the personal sampling of the inhalable fraction of airborne particles, as defined in ISO 7708 and to static (area) sampling. The analytical method is applicable to the determination of masses of 0,005 mg to 2,0 mg of sulfuric acid and phosphoric acid per sample, without dilution. The concentration range of sulfuric acid and phosphoric acid in air for which the measuring procedure is applicable is determined by the sampling method selected by the user. For an air sample of volume 1 m3, the working range is approximately 0,005 mg m-3 to 2,0 mg m-3. The method is not applicable to the determination of sulfur trioxide. The procedure does not allow differentiation between the acids and their corresponding salts if both are present in the air. The procedure does not allow differentiation between phosphoric acid and diphosphorus pentoxide (phosphoric anhydride) if both are present in the workplace.