NO2

There are seven nitrogen oxides that can be found in ambient air. However, nitric oxide (NO) and nitrogen dioxide (NO2) are the two main nitrogen oxides associated with combustion sources.

Definition

Nitrogen dioxide (NO2) is a reactive gas that is formed mainly by the oxidation of NO. It is involved in harmful reactions such as those leading to tropospheric ozone or nitric acid, and is therefore a pollutant in its own right as well as a precursor to other pollutants. Under ambient conditions, both outdoors and indoors, nitrogen dioxide exists in gaseous form.

Predominant sources of emissions

The main indoor sources of this pollutant are fuel-burning cookers (wood, paraffin, natural gas, propane, etc.), fuel-burning heating systems (wood, oil, natural gas, etc.) and tobacco use.

Legislation and intervals

According to both the World Health Organization and DIRECTIVE 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe: The limit value for NO2 is 200 μg/m3 for 1 hour average and 40 μg/m3 on an annual average.