The reduction of nitrogen oxide emissions remains among the main technological issues in engine design and has been traditionally based on empiricism, as the very details of the pertinent processes can not be probed either experimentally or numerically. Recent advances in computer hardware and software provide hope that detailed modeling of engines may be possible in the near future. Such modeling, however, will require the use of reliable fluid mechanics, as well as chemical models. While nitrogen chemistry is well understood at low pressures, at pressures of relevance to engines, its validity remains questionable. In view of these considerations, a detailed numerical investigation was conducted on the effects of the addition of nitrogen containing compounds on the laminar flame speeds and extinction strain rates of H-2/O-2/N-2 and CO/H-2/air flames. The main goal of the study was to introduce a new experimental methodology that would allow for the validation of nitrogen kinetics. The simulation was performed for one dimensional, planar, premixed flames for determination of laminar flame speeds, as well as for the opposed jet, strained, laminar premixed and non-premixed flames for the determination of extinction strain rates. The results indicate that the addition of nitrogen containing compounds can affect significantly these global properties. Furthermore, sensitivity analyses showed that there is a large number of nitrogen reactions which can be validated by using this approach, and these reactions depend on the additive type, the equivalence ratio, the pressure and the phenomenon of interest. Further studies of H-2/N2O/N-2 and CH4/N2O/N-2 flames showed that their laminar flame speeds and extinction strain rates are also sensitive to the nitrogen elementary kinetics. Thus, it is proposed that such model mixtures are used for validation of the nitrogen kinetics in flames. The main advantage of the proposed approach is that the laminar flame speeds and extinction strain rates can be experimentally determined conveniently by measuring velocities in the hydrodynamic zone of the flame, so that resolution of the details of the flame zone is not required, and this is especially important at high pressures. The detailed analysis of the flame structure revealed that the effect of the addition of nitrogen containing compounds on the response of H-2/O-2/N-2 and CO/H-2/air flames is of both thermal and kinetic nature. In particular, it was found that the NO addition has a catalytic effect on the flame dynamics, since it participates in a reaction cycle leading to the consumption of active H, O, and OH radicals by nitrogen containing species and results in reduction of the laminar flame speeds even though the flame temperature is essentially unaffected.