Home Newsletter Archive October 2010 through June 2011 What is Nitrogen Oxide?
What is Nitrogen Oxide?

by: Agency for Toxic Substances & Disease Registry


Nitrogen oxides are a mixture of gases that are composed of nitrogen and oxygen. Two of the most toxicologically significant nitrogen oxides are nitric oxide and nitrogen dioxide; both are nonflammable and colorless to brown at room temperature. Nitric oxide is a sharp sweet-smelling gas at room temperature, whereas nitrogen dioxide has a strong, harsh odor and is a liquid at room temperature, becoming a reddish-brown gas above 70°F.

Nitrogen oxides are released to the air from the exhaust of motor vehicles, the burning of coal, oil, or natural gas, and during processes such as arc welding, electroplating, engraving, and dynamite blasting. They are also produced commercially by reacting nitric acid with metals or cellulose.

Nitrogen oxides are used in the production of nitric acid, lacquers, dyes, and other chemicals. Nitrogen oxides are also used in rocket fuels, nitration of organic chemicals, and the manufacture of explosives. 1

For the formation of nitrogen oxides, extreme conditions are necessary. It must be very hot. Nitrogen oxides are naturally formed in flashes during thunderstorms. The air next to a flash can be heated to unbelievable temperatures of about 30,000°C. If we burn gasoline or diesel in a car engine it will not become that hot, but the combustion temperature is still about 2000°C. This is enough to oxidize nitrogen in the fuel air mixture. Another source of nitrogen oxides are forest fires, either natural or caused by humans. But in the densely populated regions of our countries with many peoples going by car traffic is the biggest source of these compounds. 2

For more information, read:

1.  http://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=396&tid=69

2.  http://www.atmosphere.mpg.de/enid/Information_ss/Nitrogen_oxides_5h4.html