Lyα escape fraction, $f_{\text{esc}}^{\text{Ly}\alpha }$, vs. intrinsic velocity dispersion σ₀. Solid, dashed, and dotted lines indicate the analytically derived approximate solution, our Eq. (12), for monochromatic Lyα radiation escaping a plane parallel slab of N_H = 10¹⁸ cm⁻² (solid lines), 10¹⁹ cm⁻² (dashed lines), and 10²⁰ cm⁻² (dotted line), respectively. For N_H = 10¹⁸ cm⁻² we show curves with E(B − V) = {0.1, 0.4, 0.7}, for N_H = 10¹⁹ cm⁻² curves with E(B − V) = {0.1, 0.4}, and for N_H = 10²⁰ cm⁻² the curve for E(B − V) = 0.1. We also show the $f_{\text{esc}}^{\text{Ly}\alpha }$ vs. ${\sigma }_0^{\text{obs}}$ pairings of the discussed sample. Scatter points and curves are colour coded by E(B − V) as indicated by the colour bar on the right. As in Fig. 11 we highlight points by red outlines that show L_Lyα/L_Hα ratios above the maximum dust screen expectation from Eq. (6).