Nitrogen oxides (NOx) are among the most hazardous combustion products and play a key role in the formation of smog, acid rain, and air quality degradation. This article examines three mechanisms of NOx formation—thermal, fuel-related, and rapid—and modern technologies for their reduction, including low-NOx and premix burners, FGR systems, SCR/SNCR methods, fuel dilution, and digital combustion optimization. The use of these solutions can significantly reduce NOx emissions and improve the environmental performance of industrial installations.