1.1 This Recommendation applies to measuring instruments (hereafter referred to as “gas analytical systems”) that serve to determine the volume fraction of SO2 and establishes the conditions and requirements with which such systems shall comply in order to meet the requirements for measurement results of the pollutant content in stationary source emissions within the OIML Member States. This Recommendation applies to gas analytical systems intended for measuring (analyzing) emissions of industrial enterprises and to gas analytical systems for controlling the technological processes whose principle of operation is based on UV absorption, fluorescence or nondispersive IR methods. It specifies the metrological and technical requirements for gas analytical systems, as well as the means and methods for checking their standardized characteristics. 1.2 Restrictions 1.2.1 This Recommendation does not consider the uncertainties of the measurement results of the emissions to be determined on the spot where the gas analytical system is actually installed; these uncertainties are determined by the primary standard method on the second level of quality assurance. 1.2.2 Gas analytical system software certification problems are also beyond the scope of this Recommendation.