As a future engineer, my proffessors teach us to be concerned about pollutant emissions. I always hear about NOx production inside heat engines and turbomachinery. But little is explained about the true nature of this problem. Usually, we are told that NOx is produced at high temperatures, when Fuel to Air ratio is nearly stochiometric. I want the reasons of a chemicist about that. Why those conditions enhance NOx generation?. Which are the general conditions for NOx formation inside a combustion chamber? Thanks.