1. In this Recommendation a gas analytical system means a system that continuously measures the volume fraction of sulfur dioxide by analyzing the gas samples taken directly from the pipe or gas duct of an industrial enterprise, which includes a means for sampling and sample preparation (in the case of extractive sampling), a gas analyzer, means for accumulation, processing and storage of measurement results, means for control and adjustment of the main components of the system, an interface to connect devices measuring the gas flow parameters of exhaust emissions, and gas and electric lines of communication. 2. (ISO 7504:2001)