Respiratory diseases have become a serious health care and public health problem because of their high prevalence, high disability rate, and high economic burden. Some respiratory diseases are insidious in their onset and are not easily detected in their early stages. For example, a recent epidemiological survey shows that the prevalence of COPD among people over 40 years old in China is as high as 8.2%, and about 1/3 of them have no symptoms. Some diseases are often at a serious stage of development by the time they seek medical attention, and the opportunity for early treatment is lost. Pulmonary function tests can objectively observe the function of the respiratory system, identify lung function damage that may be overlooked, and are important for the early detection of lung and airway pathologies. The World Health Organization has established World Lung Function Day in order to raise public awareness of lung function. How is a lung function test done? Pulmonary function testing is a technique that detects the amount (lung volume) and rate (lung flow) of gas inhaled and exhaled by the lungs through a spirometer to see if respiratory function is normal. Many indicators reflecting the status of lung function can be collected through inhalation and exhalation tests. Nevertheless, this test is very simple, quick, non-invasive and generally requires no special preparation. It only takes about 10 minutes to complete a routine pulmonary function test. All we need to do is to inhale and blow into the instrument as instructed by the doctor. It is important to note that different diseases may require the collection of different pulmonary function indicators the most. Who needs a pulmonary function test? First of all, people with chronic cough, sputum and symptoms of shortness of breath, wheezing and other breathing difficulties need to have a pulmonary function test. Pulmonary function tests help establish the diagnosis of the disease, assess the severity of the disease, and also guide the development of a treatment plan for the disease. Secondly, people who have no respiratory symptoms but have high risk factors for respiratory diseases also need to have pulmonary function tests. These include the following groups: 1. Heavy or long-term smokers and passive smokers. Because smoking can damage our airways, leading to reduced lung function and even the development of chronic obstructive pulmonary disease. In the early stage even if there is a decrease in lung function, there can be no conscious symptoms, and often when the decrease in lung function is more obvious, you will feel shortness of breath and difficulty in breathing. Pulmonary function test can detect COPD at an early stage and provide early treatment. 2.People who work in special environment. If the work environment, exposure to polluting gases, dust, etc., can lead to occupational lung disease and reduced lung function. Regular checkups can help detect the disease early.