Nitrogen Oxides

Nitrogen oxides, or NOx, is a term for various highly reactive compounds that contain nitrogen and oxygen.  NOx is emitted from the combustion of fossil fuels, especially at very high temperatures.  Vehicles and power plants are the principal emitters of NOx, which contributes to the formation of photochemical smog (ground-level ozone) and to acid deposition, or acid rain.

Nitrogen dioxide, one of the NOx chemicals, is a criteria pollutant regulated by the EPA, and can be seen, along with other particles in polluted air, as a reddish-brown haze.  The health impacts from NOx include respiratory problems, heart conditions, and lung damage, and if NOx reacts with common organic chemicals, it forms toxics that can cause biological mutations.

NOx is emitted at oil and gas operations from flaring, and is part of exhaust from diesel and natural gas engines that power machinery such as compressor engines and other heavy equipment.