Predicted normalised (at  ± 5900 km s^-1) Lyα line profiles for an expanding shell with v_exp = 150 km s^-1, b = 40 km s^-1, log N_HI = 20.8 cm^-2, and varying dust content described by τ_a = 0., 0.2, 0.5, 1., 1.5, 2., 3. and 4 (from top to bottom). Note how the increasing dust content progressively reduces the line to “carve” out a damped (Voigt-like) profile for the highest dust contents.