Comparison of Balmer lines Hβ, Hγ, Hδ, Hε, and selected lines of He I in synthetic spectra (T_eff = 20 000 K, log g = 2.50, and ξ =10 km s⁻¹ ) calculated with ADS (blue lines) and TLUSTY/SYNSPEC (black lines). The dotted blue lines correspond to a model computed with SURFACE only on an ATLAS 12 atmospheric structure, i.e. representing an LTE solution using otherwise the same input data as in the ADS non-LTE model.