Nitrous Oxide (N₂O) is produced directly from fuel combustion. It has been determined that, in general, lower combustion temperatures cause higher N₂O emissions. The mechanisms of N₂O chemistry seem to be relatively well understood, but experimental data are limited.

N₂O emissions from vehicles have only recently been studied in detail. Emission controls on vehicles (especially catalysts on road vehicles) can increase the rate of N₂O generation. The degree to which N₂O emissions have increased (or decreased) depends upon factors such as driving practices (i.e., number of cold starts) and the type and age of the catalyst. N₂O emissions from mobile sources for many Annex I Parties with a high number of road vehicles with emission controls, therefore, can be significant.

Table 1-8. IPCC N₂O Default Emission Factors

Updated Emission Factors for USA Gasoline Vehicles