NOxcontaining

NOxcontaining is a descriptive term used to refer to chemicals or mixtures that include nitrogen oxides, most commonly the NO and NO2 pair collectively known as NOx. In environmental science and chemistry, NOxcontaining materials are identified by their potential to release or form nitrogen oxides during processing, use, or exposure.

The principal nitrogen oxides involved are nitric oxide (NO) and nitrogen dioxide (NO2). Together they are referred to as NOx. Other dinitrogen oxides such as N2O3, N2O4, and N2O5 are related species that can participate in atmospheric equilibria, but NO and NO2 are the most commonly addressed components in regulatory and practical contexts.

Major sources of NOx include high-temperature combustion in motor vehicles, power plants, and industrial furnaces. Natural sources such as lightning also contribute. In the atmosphere, NO emitted from fuels rapidly converts to NO2, and NOx participates in photochemical reactions that generate ozone and secondary particulate matter, influencing air quality and climate.

Health and environmental effects of NOx are well documented. NO2 can irritate the airways and exacerbate respiratory conditions. NOx also contributes to the formation of ground-level ozone and fine particles, which have broader implications for human health, ecosystems, and visibility.

Measurement and regulation focus on ambient NOx levels and emissions from sources. Common metrics include parts per billion or micrograms per cubic meter for ambient air, and mass-based limits for exhaust. Mitigation strategies address NOx formation at the source, using technologies such as selective catalytic reduction, exhaust gas recirculation, and other catalytic or combustion optimization methods, as well as fuel switching and improved energy efficiency.