Properties of infrared hydrogen lines of YSOs

Based on the non-LTE model for compact HII regions around YSOs we derive linear relationships between the line ratios Pfγ/Brα and Brγ/Brα, and between Pa7/Brα and Brγ/Brα. These relationships can be used to estimate the foreground extinction provided observations of three lines are available. We also point out that the line excess phenomenon in YSOs can be explained by a proper choice of the central source and wind. Results for some IR sources are given.