For normal people, a chest X-ray is recommended once a year, during a medical checkup. The amount of radiation received for conducting 1 chest X-ray is very small and has basically no effect on the human body. When suffering from a disease, the number of examinations is decided according to the disease, such as pneumonia patients, X-ray examination of the lungs with infection, after anti-inflammatory treatment by doctors, need to understand the changes in the disease, whether the infection site has been absorbed, it is recommended to take another chest X-ray after 2 weeks, if not completely absorbed, it is recommended to take another chest X-ray after 1 month, until the infection site is completely absorbed, you can no longer re-examine the chest X-ray.