This document specifies the standard reference method (SRM) based on an automatic method for determination of the mass concentration of hydrogen chloride (HCl) in ducts and stacks emitting to the atmosphere. It describes the sampling and gas conditioning system. This document specifies the characteristics to be determined and the performance criteria to be fulfilled by portable automated measuring systems (P-AMS) using the infrared measurement method. It applies for periodic monitoring and for the calibration or control of automated measuring systems (AMS) permanently installed on a stack, for regulatory or other purposes. A number of performance characteristics with associated minimum performance criteria are specified for the measuring system (see EN 15267-4:2017, Table 1 which gives an overview of the relevant performance characteristics and performance criteria). This document can be used as a SRM provided the expanded uncertainty of the method is less than 20 % relative at the daily Emission Limit Value (ELV), or 1 mg/m 3 for ELV below 5 mg/m 3. This document specifies criteria for demonstration of equivalence of an alternative method (AM) to the SRM by application of EN 14793.