Nitrogen oxides

Nitrogen oxides are reactive compounds made from nitrogen and oxygen, especially nitric oxide (NO) and nitrogen dioxide (NO₂). They form in combustion and atmospheric chemistry and affect air quality and climate.

Nitric oxide: Nitric oxide (NO) is a colorless reactive gas produced in combustion and by biological processes. It is emitted directly and rapidly reacts with oxygen to form nitrogen dioxide.
Thermal NOx: Thermal NOx is nitrogen oxide formed when nitrogen and oxygen in air react at high combustion temperatures. It explains much of the NOx formed in engines and industrial burners.
Chemiluminescence NOx analyzer: A chemiluminescence NOx analyzer measures nitric oxide through light emitted in its reaction with ozone. It is a standard method for monitoring NO and, with conversion, total NOx.
Nitrogen dioxide exposure: Nitrogen dioxide exposure is inhalation of NO₂, an irritant gas associated with respiratory effects. It captures the direct health risk posed by a prominent nitrogen oxide.
Nitrogen dioxide: Nitrogen dioxide (NO₂) is a reddish-brown reactive gas formed in combustion and atmospheric reactions. It is a major harmful nitrogen oxide and a key participant in ozone-forming chemistry.
Prompt NOx: Prompt NOx is nitrogen oxide formed rapidly from atmospheric nitrogen during hydrocarbon combustion. It is a distinct flame-formation pathway alongside high-temperature thermal NOx.
Selective catalytic reduction: Selective catalytic reduction removes nitrogen oxides from exhaust by reacting them with ammonia over a catalyst. It is widely used to reduce NOx from power plants and diesel engines.
Acid rain: Acid rain is precipitation made unusually acidic by sulfuric and nitric acids formed from air pollutants. Atmospheric oxidation of nitrogen oxides produces nitric acid that acidifies rain.
Photolysis: Photolysis is the chemical breakdown of a molecule by absorbing light. Sunlight splits NO₂, producing oxygen atoms that help form ground-level ozone.
Fuel NOx: Fuel NOx is nitrogen oxide produced when nitrogen bound in fuel is released and oxidized during combustion. It links emissions to the nitrogen content of coal, oil, and other fuels.

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