Chest X-ray examinations are generally not harmful to the human body. The normal radiation dose received by the human body in 1 year is 3 international units, and the radiation dose from 1 chest x-ray is about 1 radiation unit, so a normal person can usually tolerate 3 chest x-rays in 1 year. In general, the longer the exposure time, the more radiation dose you will receive when you have a radiological examination. It takes about 10 seconds to do a chest X-ray, while a chest X-ray takes about 0.1 or 0.2 seconds. Therefore, it is recommended that patients try to choose chest X-ray when they undergo a physical examination, because the exposure time of chest X-ray is shorter, which is only 0.1 or 0.2 seconds, and the radiation dose received is less. Of course, if you have to choose chest X-ray for examination, it is also recommended that the patient should not do chest X-ray more than 3 times within 1 year, so as to effectively avoid the radiation damage caused by chest X-ray.