In an effect to investigate the influence of heat losses to the atmospheric enviroment on NOx formation in a CH4/air fueled combustor, we performed a parametric study in a perfectly surred reactor (PSR). The PSR code in conjunction with Chemkin II was used to conduct the numerical analysis for various parameter adjustments which were made to vary NO., formed in the reactor over a wide range of conditions. The parameter adjustments include variations in the residence time and the heat transfer coefficient at art equivalence ratio of 0.9 that can influence the reactor temperature and thus NO, formation. The numerical results indicated that the NO concentration in the reactor varied in a similar pattern as the reactor temperature over the residence time for given heat loss conditions. This wits due to the fact that net NO production rate (which is the sum of total NO production and consumption rates) wits nearly identical to thermal NO Production rate (which is sensitive to changes in the reactor temperature), This. interesting result enabled us to correlate the reactor temperature coupled with variations in the residence time and heat loss condition with the NO concentration in the reactor.