LeNOX is designed for power plant boilers fulfilling stringent emissions requirements. This achievement of technology is based on staged combustion. Fuel is led into different zones of the flame. Combustion air is divided into individually controlled chambers in wind box and directed also in stages to the flame. These fuel and air flows cause optimal air envelopes inside and around the flame, resulting in long residence time and low emissions. If the requirements of emission levels are very demanding, flue gas recirculation is an option to LeNOX.