Using the LLA-C mechanism, we have modeled changes in the O3 concentration under a wide variety of eight initial reactant conditions of [NMHC]/[NOx] = 1.0, 3.0, 7.1, 14.3, 28.6, 57.2, 100.0, 200.0 at high NOx concentrations. Simulations indicate that the amount of O3 formation is not very sensitive to changes of the NMHC distribution but mainly dependent on the NOx concentration when the [NMHC]/[NOx] is greater than or equal to 15.0. But at low nonmethane hydrocarbon-to-NOx ratios (<7.0) the predicted O3 concentration strongly depends on the amount of NMHC in a mix. This is a first exploration and much work on validation is needed.