NOx refers to a group of nitrogen oxides, primarily consisting of nitrogen monoxide (NO) and nitrogen dioxide (NO2). These gases are produced during combustion processes, such as in vehicles, power plants, and industrial facilities. NOx plays a significant role in air pollution and can contribute to the formation of smog and acid rain, which can harm both the environment and human health. The presence of NOx in the atmosphere can lead to respiratory problems and other health issues for people, especially in urban areas with high traffic. To combat NOx emissions, regulations and technologies, such as catalytic converters in vehicles and selective catalytic reduction in power plants, are implemented to reduce their release into the air.