This document specifies a method for the determination of nitrogen oxides (NOx) in flue gas 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 NOx 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: — chemiluminescence (CL); — infrared absorption (NDIR); — Fourier transform infrared (FTIR) spectroscopy; — ultraviolet absorption (NDUV); — differential optical absorption spectroscopy (DOAS); Other equivalent instrumental methods such as laser spectroscopic techniques can be used provided they meet the minimum performance requirements specified in this document. The measuring system can be validated with reference materials, in accordance with 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 F.
