Stickstoffdioxid, also known as nitrogen dioxide (NO2), is a reddish-brown gas with a characteristic sharp, acrid smell. It is a significant air pollutant, primarily produced from vehicle emissions and industrial processes. NO2 can contribute to the formation of smog and acid rain, which can harm the environment and human health. In the atmosphere, Stickstoffdioxid plays a role in the formation of ozone at ground level, which can lead to respiratory problems in humans. It is also involved in the nitrogen cycle, where it can be converted into other nitrogen compounds. Monitoring and reducing NO2 levels is essential for improving air quality.