Air pollution refers to the phenomenon that some substances enter the atmosphere due to natural disasters and human production and living activities, changing the chemical, physical and biological characteristics of the atmosphere, thus affecting people's lives and work, endangering human health, affecting the survival of various animals and plants, and directly or indirectly damaging equipment and buildings.

Air pollution source is the source of air pollutants, mainly in the following three ways:

(1) Industry: Industry is an important source of air pollution. There are many kinds of pollutants discharged into the atmosphere by industry, including smoke, sulfur oxides, nitrogen oxides, organic compounds, halides, carbon compounds and so on. Some are smoke and some are gas.

(2) Living stoves and heating boilers: A large number of living stoves and heating boilers in cities need to consume a lot of coal, and coal will release a lot of harmful substances such as dust, sulfur dioxide and carbon monoxide to pollute the atmosphere during combustion. Especially when heating in winter, it often makes the polluted area filled with smoke and makes people cough, which is also a pollution source that cannot be ignored.

(3) Transportation: Cars, trains, planes and ships are the main means of transportation at present, and the waste gas produced by burning coal or oil is also an important pollutant. In particular, the number of cars in cities is large and concentrated, and the pollutants discharged can directly hit people's respiratory organs, which has caused serious air pollution in cities and has become one of the main sources of air pollution in big cities. The exhaust gas emitted by automobiles mainly includes carbon monoxide, sulfur dioxide, nitrogen oxides and hydrocarbons, and the first three substances are very harmful.