Emissions of nitrous oxide (N2O) have been analyzed from industrial boilers and from a large experimental combustor burning natural gas, oil, or coal. Production of N2O and production of NOx were observed to be correlated, with an average molar ratio of 0.58:1 (N2O-N: NO). The content of fuel nitrogen plays an important role in determining emissions of both N2O and NOx. In conventional single-stage combustors, about 14% of fuel nitrogen is converted to N2O and 24% is converted to NOx. Conversion of fuel nitrogen to N2O was much less efficient (2–4 %) in a two-stage experimental combustor and in wood fires. A model is presented describing emissions of N2O globally, from the beginning of the industrial revolution to the present. Combustion of fossil fuel is estimated to release 3.2×106 tons N2O (as N) y−1 at present, with 83% of this derived from burning of coal in large industrial boilers. The biospheric source of N2O is calculated as 8.8×106 t y−1. The tropospheric concentration of N2O in 1860 is estimated to have been 280.7 ppb. We expect that concentrations of N2O should rise more than 20% to about 367 ppb by the year 2050, based on conservative projections of world energy consumption.