Column densities of Fe in equilibrium and the time-evolving condition. The upper panel shows the total column density of Fe in equilibrium, with each individual component plotted in a different color. To capture the wide range of concentrations, which span several orders of magnitude, a logarithmic scale is employed. The lower panel compares the equilibrium column density (represented as a dashed black line) to the average column density of time-dependent photoionization, with gas densities of 10⁸ and 10¹⁴ m⁻³ shown as blue and red lines.