because of air jets and a lean burning zone which further oxidizes the remaining UHC and CO [2]. There are some improvements in LP and RQL original concepts to produce combustion devices with extremely low NOx emissions. For example: Lean Pre-mixed Burner with Spatially Periodic Recirculation of Combustion Products [3]; Double Swirler Lean Premixing Pre-Vaporizing Burner [4]; Rich-Burn,Quick-Mix, Lean Burn Trapped Vortex Combustor [5]; Rich-Catalytic Lean-Burn Combustion