Secondhand smoke is a major factor that harms non-smokers around smokers. First of all, because it contains a very large number of harmful chemicals, such as carbon monoxide, tar, nicotine, etc., most of them are released through incomplete combustion of tobacco, these harmful components into the lungs of the surrounding healthy people, so that the lung mucosa of these people suffer different degrees of injury, or even degeneration. Such as easier to lead to pneumoconiosis, silicosis, the lungs can appear different degrees of diffuse fibrosis, calcification, can cause chronic bronchitis, chronic obstructive emphysema, and even cause chronic pulmonary heart disease, may also induce bronchial asthma. If exposed to secondhand smoke for a long time, over time, it may also cause malignant tumors of the lung, such as bronchopulmonary cancer and alveolar cell carcinoma.