The following equation can be used to correct a measured pollutant concentration in an emitted gas (containing a measured O content) to an equivalent pollutant concentration in an emitted gas containing a specified reference amount of O:
Thus, a measured  concentration of 45 ppmv (dry basis) in a gas having 5 volume % O is<br>
45 × ( 20.9 - 3 ) ÷ ( 20.9 - 5 ) = 50.7 ppmv (dry basis) of  when corrected to a gas having a specified reference O content of 3 volume %.