Sub-DLA detected towards QSO J0008-2900 at z_abs = 2.254. The solid red line shows the Voigt profile fit to the sub-DLA with an inferred column density of log N_H   I = 20.22 ± 0.10. The system is detected down to Lyβ. Here and in the following figures, the dotted blue line represents 1σ error on the spectrum. The vertical dotted line is the adopted zero velocity corresponding to the redshift of the sub-DLA. The horizontal line is at a level of one.