The large number of possible chemical reactions represents a severe burden for modeling of even relatively simple plasma systems. Reduced sets of chemical reactions have been obtained for numerical simulations of nitrogen and nitrogen-hydrogen plasma jets flowing into an atmospheric air environment. The important or active reactions are determined based on a simplified reduction method. A reaction is considered active if it leads to higher sensitivities than a specified cutoff sensitivity of 1%. The active reactions exert a significant influence on main plasma parameters, such as velocity, temperature, and species concentrations. The sensitivity analysis for the specified systems shows that two NO reactions, known as Zel＇dovich reactions (N-2 + O <-> NO + N and NO + O <-> O-2 + N),((I)) are both active in a nitrogen plasma jet. On the other hand, the latter is not active and may be omitted in a nitrogen-hydrogen plasma jet. A nitrogen-hydrogen plasma jet requires contribution of two active charge exchange reactions: N-2 + N+ <-> N-2(+) + N and N + H + <-> N + + H, while only the former is needed in a nitrogen plasma jet. The dissociation reactions are all active in both plasma jets, except the dissociation of OH.