Notes: According to p. 204 of radiation safety rules, the requirements to the radiation protection against exposure caused by natural radiation sources impact in working conditions are made to the objects where the annual exposure of personnel from natural radiation source exceeds 1 mSv. According to the p.206.2 of the same rules, the annual average volumetric activity of radon in equilibrium in air of production use buildings shall not exceed 300 Bq/m3, and the gamma radiation dose equivalent - 0.6 μSv/h.  