The main gas responsible for air pollutants is nitrogen dioxide (NO2). This gas is primarily produced from vehicle emissions, industrial processes, and power plants, contributing to smog, respiratory problems, and environmental degradation. NO2 is classified as part of a group of gases known as nitrogen oxides (NOx), which can also form secondary pollutants like ground-level ozone when combined with volatile organic compounds (VOCs) in the presence of sunlight. Reducing nitrogen dioxide emissions is vital for improving air quality and protecting public health.