According to the national standard GB 15208.1-2005, the dose of a single examination of an X-ray screening device should not be greater than 5μGy, and at the same time, the dose of X-rays in any place 5cm away from the outer surface of the device (including the entrance and exit of the device) should be less than 5μGy/h.
350nGy=0.35μGy
Roughly equivalent to one percent of the chest X-ray