Radon in underground mines, excavation sites and tunnels

Radiation and Nuclear Safety Authority (STUK) monitors the exposure of workers to radon. According to Section 145 of the Radiation Act, the party responsible must notify STUK of mining activities within the meaning of the Mining Act, as well as extraction work or other work carried out in underground passages or tunnels where the total annual working time of one employee exceeds 100 hours. The notification must be made in writing before commencing the practice.

Make the notification 

(Both notifications can be made on the same form. The form can also be found on STUK's Finnish
 webpage E-services and forms).

Reference levels

The reference level for the radon concentration at the workplace is 300 becquerels per cubic metre in a space where people work for 600 hours or more per year. The reference level for occupational exposure to radon is 500,000 becquerel hours per cubic metre (Bq h/m3) per year. Exposure is calculated as the sum of the exposures in all workspaces during the year. The reference level for occupational exposure to radon is not applied if the worker only works in a space where the radon concentration is lower than the reference level for the radon concentration in indoor air at the workplace.

Measurements

According to the STUK regulation, the radon concentration must be measured as follows:

  • at underground excavation sites: every six months; however, if the result of two consecutive measurements is lower than 100 Bq/m3 at all measurement stations, the radon measurement interval can be extended to one year
  • in underground mines: every other year; however, if the result of three consecutive measurements is lower than 100 Bq/m3  at all measurement stations, the radon measurement interval can be extended to five years.

In underground mines, at excavation sites and in tunnels, measurements are conducted:

  • in excavation pits where excavation is being carried out;
  • in underground maintenance facilities and break rooms used; and
  • other underground work sites that are constantly used.

Radon measurements are also conducted during post-excavation construction and finalisation work.

Radon measurements of at least two months, which are required in typical workplaces, are often not possible in underground mines and excavation sites. Therefore, radon levels are often measured from short-term air samples taken from the workplace.

Except for radiation safety, the safety of mines is supervised by the Finnish Safety and Chemicals Agency (Tukes).

Further information

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