Low-NOx Burners are designed by using controlled air-fuel mixing. They are standard features on almost all recently built boilers. They reduce NOx by up to 80 percent. The low NOx burner technology restricts airflow into the combustion chamber, which lowers combustion temperatures and NOx formation. Low-NOx burner achieves typical emission reductions of between 40% and 50%, with up to 70% reduction claimed for large new boilers. Emission reduction by low NOx burners are achieved by lowering of combustion temperatures but the cleaner operation of the retrofitted boilers should more than compensate for any possible consequential loss in efficiently. Low-NOx burners are used to control NOx emissions from gas turbines. A low-NOx burner is a hydrocarbon fuel burner with internal recirculation flue gas and staged fuel combustion. This is provided with the combustion air staged input and the burner is shaped like a convergent-divergent nozzle.