Radon at the workplace

The main goal of radon control is that no worker in Finland is excessively exposed to radioactive radon gas that may cause lung cancer. Control contributes to ensuring that any measures that are potentially needed at workplaces are scaled appropriately and taken sufficiently quickly.

The Radiation and Nuclear Safety Authority (STUK) supervises compliance with the Radiation Act (859/2018) and decrees and regulations issued by virtue of it (section 14 of the Radiation Act), unless oterwise stated.

Workplaces requiring a radon concentration analysis

It is the employer’s duty to have the radon concentration of the workplace measured at least in the following cases:

  1. in all work spaces that are located wholly or partly underground in the whole country.
  2. in areas where more than 10 per cent of the radon concentrations measured earlier exceeds the value of 300 Bq/m³. STUK maintains a list of such areas.
  3. at workplaces throughout the country if they are located on ridges or very air-permeable gravel or sand formations
  4. in an installation that distributes household water where the water does not derive solely from a body of surface water and has contact with indoor air.

Measurement must be conducted in spaces where people work for at least 20 hours per year (= approximately 6 minutes per day). Radon measurement is not usually needed at workplaces that are located on the second or upper floors. In these locations, the radon concentrations are generally low.

Procedures after the measurement

If the workplace radon measurement has been conducted using boxes from STUK’s radon measurement service, the radon measurement service sends a result report to the customer. The STUK's radon measurement service delivers the measurement results to STUK’s Natural Radiation Regulation Unit.

If the radon measurement has been ordered from a private radon measurement company, the employer must notify STUK immediately of the radon measurement results. The notification is submitted via the electronic service (in Finnish) and the measurement results must be attached to the notification. All measured radon concentrations, also the small ones, must be notified to STUK. All results are saved in the national radon database.

According to Radiation Act 859/2018, §146 and §155 the employer must notify the radon measurement results made at the workplace. The notifications are made via the electronic service:

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The measurements ordered from STUK don't have to be notified.

Reference values for radon

The radon concentration during working hours for regular work (over 600 hours per year) must not exceed 300 becquerels per cubic meter (Bq / m³). The radon concentration is calculated as the annual average of the radon concentration during working hours (measurement result x 0.9).

The reference value of occupational exposure for radon is 500,000 becquerel hours per cubic meter per year. Exposure is calculated as the sum of the exposures accumulated during the year in all workspaces.

Measuring the radon concentration

The radon concentration in air at the workplace is determined primarily using a radon measurement box (integrating measurement) that is kept at the workplace for a minimum of two months between the beginning of September and the end of May. The radon measurement box indicates the long-term average concentration. After this, if necessary, time-associated variations in the radon concentration can be analyzed with so-called continuous radon measurement.

A key point in radon control at workplaces is that a reliable method of measurement is used when determining the radon concentration. Radon measurement can be ordered from a company that uses a method of measurement approved by STUK.

Radon measurement aims at determining workers’ exposure to radon so measurement stations and the number of measurement boxes needed are selected accordingly:

  • At least one measurement must be made in each separate building. If a building has several ventilation systems, measurements must be conducted separately for the areas covered by each ventilation unit.
  • Workplace radon measurement is conducted on the first floor (seen from the ground level) of the building and in those spaces underneath the first floor where people work or personnel rooms are located. If the workplace must undergo measurement due to the fact that it has spaces located wholly or partly underground, measurements must be conducted at least in the underground spaces.
  • If the workplace is located in a space that is equivalent to a dwelling, measurement is conducted with two measurement boxes.
  • Each workplace is measured with at least two boxes unless the total work space area is small (less than 100 m2).
  • If the working area is greater than 200 square meters, at least one measurement per each 200 square meters must be made or in a single open space (e.g. halls), at least one measurement for each 3000 square meters.

Radon measurement should be repeated if ventilation has been substantially changed in connection with renovation. Re-measurement is also necessary when floor structures have been opened up for reasons such as water damage. Re-measurement is also recommended if more than ten years have passed since the last measurement and the result of the last measurement exceeded 300 Bq/m³.

What to do if the measured radon concentration is higher than the reference value?

If the radon concentration measured exceeds the reference value, the employer must conduct additional analyses or perform measures that reduce the radon concentration and thereby also the worker’s exposure to radon. STUKs Inspector will contact the employer and ask for additional information. After this, STUK will give demands to the employer for further measures to be taken and deadlines to carry them out. A few examples:

  • In properties where ventilation is set with timing, the radon concentration may be considerably lower during working hours than at other times. If the radon concentration measured with a box in such property exceeds the action level, so-called continuous radon measurement may be conducted, for a minimum of one week.
  • Workplaces where the action level is exceeded are ordered to take measures to reduce the radon concentration, that is: to perform radon mitigation. The planning of workplace radon mitigation is subject to the same rules as radon mitigation for dwellings.
  • If the radon concentration revealed by the first measurement is exceptionally high or the radon concentration cannot be decreased below the action level, despite measures taken at the workplace, the employer arranges a regular monitoring of radiation exposure for the workers. In this case, each worker’s effective dose is recorded in the dose register maintained by STUK.

If measures to reduce the radon exposure are to be taken at the workplace, these measures must be taken without delay. The adequacy of the measures must be verified by equivalent measurements or calculations that have shown earlier the radon concentration or radon exposure to exceed the reference value. The results of the measurements must be reported to STUK.

Workers’ radiation protection

Radon can be found everywhere, even in the open air in small concentrations. Radon does not have a threshold value, or a non-harmful concentration. The higher the concentration and the longer the exposure, the higher the lung cancer risk.

The reference value is an agreed value that serves as the upper limit for the concentrations that a worker may be exposed to. However, the goal for workplaces should always be as low radon concentration in air as practically possible. All manners of reducing the radon concentration reduce the cancer risk caused by radon.

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