The same as other diseases, slow-onset lung can also be screened by physical examination, which can achieve early detection, early diagnosis and early treatment, thus delaying the disease process of slow-onset lung, promoting lesion regression and functional recovery, and maintaining a better quality of life. People with susceptibility to and risk factors for slow-onset lung should be screened: those born premature or malnourished or with recurrent respiratory infections as children, those with family history or siblings who have suffered from slow-onset lung but are asymptomatic, those with a history of chronic cough or chronic bronchitis for more than 5 years, those who have smoked continuously for more than 10 years, and those with long-term occupational exposure. For normal people, a cough with sputum for more than two weeks and a chest sound during coughing should be followed by a pulmonary function test at a hospital. The results of the pulmonary function test can help determine whether or not the person is suffering from chronic obstructive pulmonary disease. The purpose of the test is to understand the physiological status of the respiratory system, to identify the mechanism and type of pulmonary dysfunction, to determine the extent of the disease, to estimate the functional reserve of the lungs, and to provide a basis for dynamic observation of the evolution of the disease process, pre-surgery or health examination. The tester only needs to blow a breath into a specific machine. This breath includes two objective indicators: maximum ventilation and time lung volume. The gas exhaled by the tester after 20 seconds of repeated breathing is already similar to the alveolar gas. And the lower the alveolar oxygen content, showing the stronger the ventilation function, and vice versa, the higher also weaker. As the alveolar breathing area can be reduced due to lung lesions, so that the diffusion of gas in the pulmonary capillaries is impaired, or due to the relationship between alveolar wall lesions, resulting in reduced gas permeability, the gas exchange function can be weakened.