The procedure is applicable from a minimum of 30 mg/m3 by reference to sampling periods of mormally 30 min. At mass concentrations greater than 2 000 mg/m3 the volume of the waste gas under investigation passed through the sampling train is 30 litres. Substances, which are known to have an effect on the titration reading are given. All concentrations are based on dry gas at a temperature of 273,1 K and a pressure of 101,3 kPa.