The term "nitrogen oxides" - NOx is usually used to include two gasses - Nitric oxide - NO, which is a colourless, odourless gas and nitrogen dioxide and NO2, which is a reddish-brown gas with a pungent odour.
Common name: Oxides of nitrogen, nitrogen dioxide, nitric oxide and NOx.
Both nitrogen dioxide and nitric oxide is used in different chemical processes e.g. as a powerful oxidising agent. Nitrogen dioxide is also used in the manufacturing of nitric acid.
Release from the environment
Major man-made releases of nitrogen oxides are primarily from fuel combustion, biomass burning and some production processes.
Impacts on the environment and human health
Nitrogen oxides contribute to acid rain, eutrophication, photochemical air-pollution, and depletion of the ozone layer and have detrimental effects on health. High levels of nitrogen dioxide and nitric oxide are damaging to plant life. They can hinder growth and stress plant life making it more susceptible to other effects such as disease and frost damage. Excessive exposure to nitrogen oxides may cause health effects on the respiratory organs.
Nitrogen oxides are controlled by the Gothenburg Protocol under the Geneva Convention on Long-Range Transboundary Air Pollution and the EU NEC (National Emission Ceiling) directive especially on sulphur dioxide, nitrogen oxides, hydrocarbons and ammonia. Furthermore nitrogen oxides are on the EU-Commissions EPER list and listed in the PRTR Protocol under the Århus Convention.
Nitrogen dioxide: 10102-44-0
Nitric oxide: 10102-43-9