Final answer:
Leakage radiation from protective housing of a device like an X-ray machine must be less than 1 mR/hr at a distance of 1m, following safety regulations to prevent harmful effects.
Step-by-step explanation:
The question pertains to the maximum permissible levels of leakage radiation from protective housing of a radiation-emitting device, such as an X-ray machine. According to radiation protection standards, leakage radiation must be less than 1 mR/hr at a distance of 1m from the protective housing. This is a measure intended to limit the exposure to radiation for both occupational workers and the general public, ensuring safety from potential harmful effects of radiation.