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 

• Notification for extraction work or other work carried out in an underground passageway or tunnel (Formbox, in Finnish)
• Notification of a site for mining activities and the management, use, storage and utilization of materials and waste containing natural radioactive substances within the terms of the Mining Act and a general description of the work, (Formbox, in Finnish) 

(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. 

Radon 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.

Radon measurements must be carried out to ensure that the radon exposure of workers can be assessed as reliably as possible. The STUK Guide. Radon measurements in underground mines. November, 2025 (only in Finnish) provides advice on conducting radon measurements in underground mines. The methods are also suitable for radon measurements at underground excavation sites.

Radon measurements for underground mines, excavation sites and tunnels can be ordered here Measurement of radioactivity in samples under "Radon measurements of underground mines, excavation sites and tunnels".

Further information

• STUK Guide. Radon measurements in underground mines. November 2025. (Only in Finnish) (Julkari)
• The Finnish Safety and Chemicals Agency (Tukes) 
• Radiation Act 859/2018 (Finlex) 
• Radiation and Nuclear Safety Authority Regulation on Practices that Cause Exposure to Natural Radiation (STUK S/6/2022) (Finlex) 
• Government Decree on Ionizing Radiation 1034/2018 (Finlex)
• Decree of the Ministry of Social Affairs and Health on ionizing radiation 1044/2018 (Finlex)