Introduction to Nitrogen Dioxide

Nitrogen dioxide (NO₂) is a reddish-brown, toxic gas with a pungent odor. It is chemically reactive and readily soluble in water, forming nitric acid and nitrite. It is an air pollutant, primarily originating from fossil fuel combustion, vehicle exhaust emissions, and industrial processes. Nitrogen dioxide has a strong irritant effect on the human respiratory system; long-term exposure can lead to chronic bronchitis, emphysema, and other diseases, and high concentrations can even be life-threatening. In environmental monitoring, nitrogen dioxide concentration is one of the important indicators for assessing air quality.