5. Reference levels are utilized in order to optimize protection for the current exposure. Priority shall be given to exposures over the reference level during optimization of protection and shall continue to be implemented below the reference level.
6. Considering the occupancy time factors, the reference levels for dwellings and workplaces, for indoor radon activity concentration expressed in terms of the annual average activity concentration in air are indicated below.
7. The indoor radon activity concentration for dwellings shall be kept below:
(a) (300) Becquerel per cubic meter (Bq.m-3) in terms of annual average activity concentration of radon in air for existing buildings.
(b) (200) Becquerel per cubic meter (Bq.m-3) in terms of annual average activity concentration of radon in air for new buildings.
8. The indoor radon activity concentration for workplaces shall be kept below:
(1000) Becquerel per cubic meter (Bq.m-3) in terms of annual average activity concentration of radon in air.