The analysis of equilibrium conditions might be irrelevant to determine the importance of a certain set of atomic data. We show, that in non-equilibrium and optically thick plasmas intercombination transitions between highly excited states as well as higher order dielectronic satellite transitions are of extraordinary importance for diagnostics. In optically thin equilibrium plasmas, however, they are almost negligible. Numerical examples are presented for neutral helium in attached/detached plasmas as well as for dense laser produced plasmas. ©2005 American Institute of Physics
