Burner for reducing nox emissions and method for operating the burner

A burner for heating a heating space with a reduction of NOx emissions, comprising:

• a mixing and combustion chamber;
• a mixing and igniting device disposed in the mixing and combustion chamber;
• a fuel feed connected to the mixing and igniting device and configured for feeding fuel to the mixing and igniting device;
• an air feed configured for feeding at least one partial air flow to the mixing and combustion chamber;
• a combustion chamber opening configured for opening the mixing and combustion chamber towards a heating space to be heated;
• control means configured for controlling a fuel flow via the fuel feed and for controlling at least one partial air flow via the air feed, wherein the burner and the control means are configured for operating the burner) with a stable flame extending from the mixing and igniting device through the combustion chamber opening into the heating space;
• and a cross-section of the combustion chamber opening relative to the burner output is in a range of between 1.5 mm2/kW and 10 mm2/kW.