Illustrations of the numerical method employed for implementing N₂ (and CO) shielding functions in this work. The plots show the fractional abundances of N₂ as functions of radii. It is seen that one can obtain the same converged results (solid lines in black) by assuming N₂ is either fully shielded (dashed line in red, left panel) or unshielded (dashed line in blue, right panel) during the first loop. The dotted lines show the intermediate abundances before reaching the final results.