Green plants use air, sunlight and carbon dioxide in water to synthesize nutrients. In this process, oxygen is released. Humans and other animals get oxygen by breathing air. Animals also need oxygen to get energy from the food they eat. The development of industry has discharged harmful substances into the air, polluted the air and increased harmful components in the air. When harmful substances in the air reach a certain concentration, it will seriously damage human health and the growth of crops, destroy some substances, reduce people's visibility and affect traffic safety. Therefore, we must make great efforts to prevent air pollution. "