This International Standard specifies sampling methods and analysis methods for the determination of the ratio of biomass- and fossil-derived carbon dioxide (CO₂) in the CO₂ from exhaust gases of stationary sources, based on the radiocarbon (¹⁴C isotope) method. The lower limit of application is a biogenic to total CO₂ fraction of 0,02. The working range is a biogenic to total CO₂ fraction of 0,02 to 1,0.