For adults, at least six months should elapse between examinations, while adolescents and children should preferably be examined once every two to three years. Chest X-ray is one of the earliest imaging examinations used in clinical practice, but the examination process generates a large amount of radioactive rays, which can cause serious damage to the human reproductive system, blood system and genes, and is the examination method with the worst safety, longest exposure time and highest ionizing radiation dose among all X-ray imaging examinations. If chest X-ray is needed, it is recommended that the time between 2 examinations should preferably be longer to ensure that the corresponding radioactive rays are discharged from the body and to reduce the impact of the rays on the human body. Patients are advised not to do chest X-ray when it is not necessary, and can choose other examination methods, such as CT and chest X-ray, which can reduce the radiation.