The smog in various parts of China is, in a general aspect, the product of pollution emissions from various sources through a series of chemical and physical processes, here there is both primary emissions and secondary chemical transformations and physical processes. From south to north The situation is very complicated. The current general situation is different from that in London and Los Angeles. Some scholars have said that the situation in Beijing is a composite of "London-type" and "Los Angeles-type". In fact, things are definitely not A "composite type" that can be summarized. It is also worrying that from the top to the bottom, coal combustion is considered to be the root cause of problems in various provinces and regions. It seems that after the city's gasification is realized, the problem can be greatly solved. In fact, our Emissions or the substances produced in the secondary process are by no means just a sulfur dioxide or a nitrogen oxide compound. The most appropriate summary of this text is:. ['Main characteristics of smog formation.', 'The causes of haze formation are complex.', 'Diversity of smog types.', 'Haze hazards are universal.']