C Iλ 1560 rest-frame equivalent width as a function of total C I column density. Red squares denote GRB C I absorbers from this work. Blue dots show the C I-selected quasar absorbers from Ledoux et al. (2015), for which Noterdaeme et al. (2018) measured the total N(C I) from high-resolution spectroscopy. The black line shows the best linear fit where the σ = 0.3 dex scatter is shown by the gray-shaded region. The approximate column density (and equivalent width) at which the intrinsic C I lines saturate are marked by the dotted lines.