In this paper a validated 2D axisymmetric plasma fluid model was used to study the influence of the level of nitrogen impurities on the processes that occur in a helium parallel plate dielectric barrier discharge. The level of nitrogen impurities was varied in the range 0.1–500 ppm. It was observed that the nitrogen impurities significantly affect the dominant ion species at breakdown and the discharge characteristics. Specifically, three different dominant ions were found, which are strongly dependent on the level of nitrogen impurities. These are: (0.1–35 ppm), (35–150 ppm) and (150–500 ppm). In addition, the results show that the discharge characteristics are dependent on the dominant ion species at breakdown.