SIST ISO 7935:2025 PDF

This document specifies a method for the determination of sulfur dioxide (SO2) in flue gases of stationary sources and describes the fundamental structure and the key performance characteristics of automated measuring systems. The method allows continuous monitoring with permanently installed measuring systems of SO2 emissions. This document describes extractive systems and in situ (non-extractive) systems in connection with a range of analysers that operate using, for example, the following principles: — non-dispersive infrared absorption (NDIR); — Fourier transform infrared (FTIR) spectroscopy; — laser spectroscopic technique or tunable laser spectroscopy (TLS); — non-dispersive ultraviolet absorption (NDUV); — differential optical absorption spectroscopy (DOAS). Other equivalent instrumental methods can be used provided they meet the minimum performance requirements specified in this document. The measuring system can be validated with reference materials, according to this document, or comparable methods. Automated measuring system (AMS) based on the principles listed above has been used successfully in this application for the measuring ranges as shown in Annex E.