Nitrogen oxides (NOX) are different nitrogen gases: Nitric oxide (NO) y nitrogen dioxide (NO2). The term NOX refers to both gases combination because of the easy mutual conversion when oxygen is present.

From a formal aspect, nitrogen oxides are comprised of the following compounds: NO, NO2, N2O2, N2O4, N2O, N2O3, N2O5 and NO3, the latter being unstable.

All of them are contaminant gases, so NOX emissions must be treated to avoid their impact on the environment, such as:

  • The destruction of the ozone layer in the stratosphere.
  • The contribution to ozone formation in lower layers of the atmophere when reacting with volatile organic compounds, which contributes to the creation of smog (photochemical) and the greenhouse effect.
  • Acid rain production, when NOs become nitric acid by contact with humidity.
  • These are very toxic for people when inhaled, especially NO2.

Part of NOX emissions are caused by natural reasons (bacterial decomposition of organic nitrogen, wildfires, volcanic activity, storms, etc.). However, the most important production is anthropogenic: fossil fuels use and combustion engine vehicles exhaust.

Learn more about selective catalytic reduction of NOx in our blog.