Nitrogen dioxide is a reddish-brown gas with a sharp, acrid smell. It is a significant air pollutant, primarily produced from vehicle emissions and industrial processes. This gas can contribute to the formation of ground-level ozone and fine particulate matter, which can harm human health and the environment. Exposure to nitrogen dioxide can irritate the respiratory system, leading to coughing and difficulty breathing. Long-term exposure may increase the risk of respiratory infections and worsen conditions like asthma. Monitoring and controlling nitrogen dioxide levels is essential for improving air quality and protecting public health.