ISO 13833:2013 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.