This Technical Specification specifies an automatic method for determination of the mass concentration of hydrogen chloride (HCl) in ducts and stacks emitting to atmosphere. It describes the infrared analytical technique, including the sampling and gas conditioning system. The method should fulfil the performance characteristics requirements of this Technical Specification and the expanded uncertainty is less than 20 % relative at the daily Emission Limit Value (ELV). In order to use an alternative method to this method, it is necessary to demonstrate equivalence according to the Technical Specification CEN/TS 14793. It is necessary that the capability to demonstrate equivalence is officially recognised by the national accreditation body or law.