This International Standard specifies a charcoal tube/gas chromatographic method for the determination of the concentration of vaporous chlorinated hydrocarbons in workplace air. The method is valid for the measurement of the concentrations of airborne vapours of any of the following compounds: a) dichloromethane; b) chloroform; c) carbon tetrachloride; d) 1,1-dichloroethane; e) 1,2-dichloroethane; f) 1,1-dichloroethene; g) 1,2-dichloroethene; h) 1,1,1-trichloroethane; i) 1,1,2-trichloroethane; j) trichloroethene; k) 1,1,2,2-tetrachloroethane; I) tetrachloroethene; m) 1,2-dichloropropane; n) chlorobenzene; o) o-dichlorobenzene. The method is valid for concentrations of airborne vapours of these compounds in the range from approximately 1 mg/m3 to 1000 mg/m3 (about 0,2 ml/m3 to 200 ml/m3; see 8.1) when sampling 10 litres of air. NOTE 1 The upper limit of the useful range is set by the adsorptive capacity of the first section of the charcoal tube (5.1) used. This capacity is measured as a breakthrough volume of air, which should not be exceeded during sampling (see clause 6 and annex A). The lower limit is set by a number of parameters, including the noise level of the detector (5.9), blank concentrations due to the contamination of the charcoal tube and carbon disulfide by the substance analysed, desorption efficiency (see annex B) and interference of the solvent peak in the gas chromatographic analysis. The method is also valid for the measurement of airborne concentrations of mixtures of these compounds. In such cases, the unique properties of each compound have to be considered when determining the volume of air to be sampled and the gas chromatographic conditions to be used. NOTE 2 When analysing chlorinated hydrocarbon mixtures with very large differences in concentrations and in which several compounds are present, the reproducibility and repeatability of the compounds of minor importance might be influenced. The method has been validated for a selection of typical chlorinated hydrocarbons[1]. This procedure is compatible with low flow rate personal sampling equipment, and can be used for personal and fixed location sampling for obtaining time-weighted-average concentrations of chlorinated hydrocarbon solvent vapours in air. It cannot be used to measure instantaneous or short-term fluctuations in concentrations. Alternative on-site procedures, such as gas chromatography or infrared spectrometry, shall be used to measure rapidly changing concentrations. Organic components which have the same or nearly the same retention time as the substance analysed during the gas chromatographic analysis will interfere. Interferences can be minimized by proper selection of gas chromatographic columns and pro-gramme conditions.