What is NOx?

NOx emissions from different sources

NOx emissions from different sources

Nitric oxide (NOx)

Nitrogen oxide (NOx) is a chemical compound of oxygen and nitrogen that is formed by reacting with each other during combustion at high temperatures, mainly combustion of fuel such as oil, diesel, gas and organic matter. NOx is a common designation of nitrogen oxides NO and NO2. NOx can cause serious health damage to humans, including respiratory diseases. NOx is also responsible for smog and the typical brown cloud that covers larger cities and produces poor air quality. NOx emissions contribute to acid rain and formation of ground-level ozone that can damage ecosystems, animal and plant life.

NOx reacts with ammonium (NH4 +), water vapor and other compounds and forms nitric acid (HNO3) and small particles.
NOx reacts with volatile organic compounds in the presence of sunlight and forms ground-level ozone. Ozone can be transported with wind over longer distances.
NOx can also easily react with common organic compounds, and even ozone, to form a variety of toxic components. NOx emissions in Norway are mainly from energy production, road traffic and shipping. Domestic shipping and fishing account for about a third of total emissions. NOx can spread over long distances if it reaches the troposphere within approx. 1 day and therefore not only a local and regional problem but can be transported over continents with a duration of approx. 5-10 days and distance of several thousand kilometers.
In Norway, the sources of NOx emissions are primarily the combustion of fossil fuels in oil and gas, industry and mobile sources on land and at sea.