A process for removing oxides of nitrogen from flue-gases by reaction with urea: CO(NH2)2 + 2NO + O2 =+ 2N2 + CO2 + 2H2O The problem with this reaction is that it takes place over a narrow temperature range, between about 930 and 1,0300C. Below this range, ammonia is formed; above it, more nitrogen oxides are formed. In the NOxOut process, proprietary additives are used to widen the usable temperature range. (Check source for accuracy of chemical formula)