Air in the chest cavity may be caused by closed pneumothorax, pulmonary atelectasis, and trauma. It can be treated by closed chest drainage surgery, thoracentesis drainage, and medication. 1. Closed pneumothorax: it is caused by rupture of lung tissue, trachea, esophagus wall, breach of chest wall, etc., so that the air from outside flows into the pleural cavity, resulting in accumulation of air in the pleural cavity, chest tightness, irritating dry cough, etc. If the amount of accumulated air is more than 30% of the volume of the chest cavity, thoracentesis can be carried out to expel the gas, and when the amount of accumulated air is more than 50%, it is recommended to carry out closed thoracic drainage. 2. Pulmonary atelectasis: it is the collapse of lung parenchyma or airlessness, accompanied by lung atrophy and respiratory dysfunction, etc. It may have symptoms such as chest tightness, shortness of breath, respiratory failure, and air in the chest cavity, etc. It can be treated with drugs such as Niclosamide and Lopressor, etc., and can also be treated with thoracocentesis and drainage to promote the exhaustion of air. 3. Trauma: trauma can cause chest wall injury or lung injury and cause chest cavity with gas, such as open injury caused by chest cavity with gas need to first open wound closure to closed pneumothorax, according to the closed pneumothorax to treat; such as lung injury caused by the injury, according to the injury situation, if necessary, need to be operated on and combined with expectorant, anti-infective and other drugs treatment. Therefore, patients with gas in the chest cavity should go to the hospital as soon as possible to clarify the cause of the disease, and under the guidance of the doctor for standardized treatment.