An interlaboratory comparison for European radon calibration facilities was conducted to evaluate the establishment of a harmonized quality level for the activity concentration of radon in air and to demonstrate the performance of the facilities when calibrating measurement instruments for radon. Fifteen calibration facilities from 13 different European countries participated. They represented different levels in the metrological hierarchy: national metrology institutes and designated institutes, national authorities for radiation protection and participants from universities. The interlaboratory comparison was conducted by the German Federal Office for Radiation Protection (BfS) and took place from 2018 to 2020. Participants were requested to measure radon in atmospheres of their own facilities according to their own procedures and requirements for metrological traceability. A measurement device with suitable properties was used to determine the comparison values. The results of the comparison showed that the radon activity concentrations that were determined by European calibration facilities complying with metrological traceability requirements were consistent with each other and had common mean values. The deviations from these values were normally distributed. The range of variation of the common mean value was a measure of the degree of agreement between the participants. For exposures above 1000 Bq/m³, the variation was about 4% for a level of confidence of approximately 95% $\left(k=2\right)$. For lower exposure levels, the variation increased to about 6%.

Natural radioactivity due to the presence of Ra-226, Th-232 and K-40 in selected building materials (cement, sand, bricks, gypsum and ceramic) used in Egypt was measured using a gamma-ray spectrometer with an HPGe detector. The average activity concentrations observed in different building materials ranged from 10.0 +/- 1.3 to 109 +/- 6, < 2 to 55.8 +/- 2.2 and 5.5 +/- 1.7 to 684 +/- 34 Bq kg(-1) for 226Ra, 232Th and 40K, respectively. Based on these, together with previously reported results, the effective doses received by the residents of different types of house within all Egyptian governorates were assessed using the WinMat computer program. The results were below 1 mSv a(-1) in all cases. The collective effective dose indoors was assessed as 15 000 man Sv and the excess effective dose due to building materials was 0.07 mSv a(-1).

Representative sampling of radon in indoor air is difficult because the concentration often exhibits unpredictable spatial and temporal variation. In workplaces, temporal variation may be rapid, and the minimum and maximum concentration can differ by a factor of 100. In this paper, we compare methods for assessing the radon concentration in workplaces utilising the results of an initial investigation with a track-etch detector and the results of an additional continuous measurement. The recommended method is as follows: the mean radon concentration during the working hours of 1 week, as well as the weekly mean, is calculated from the continuous measurement. The ratio between these mean concentrations is multiplied by the result from the track-etch detector. The coefficient of variation of this method is assessed as 19%. If the result of 1 week of continuous measurement is used alone, the coefficient of variation is assessed as 32%.

The aim of this study was to obtain information on the radon concentrations to which Finnish workers are exposed. Radon measurements were conducted as integrated measurements in 700 workplaces, supplemented by continuous radon measurements in 334 workplaces. The occupational radon concentration was calculated by multiplying the result of the integrated measurements by the seasonal correction factor and the ventilation correction factor (ratio between the working time and the full-time radon concentration obtained from continuous measurement). The annual radon concentration to which workers are exposed was weighted by the actual number of workers in each province. In addition, workers were divided into three main occupational categories (working mainly outdoors, underground, or indoors above ground). Probability distribution of the parameters affecting radon concentration levels were generated to calculate a probabilistic estimate of the number of workers exposed to excessive radon levels. With deterministic methods, the geometric and arithmetic mean radon concentrations in conventional, above-ground workplaces were 41 and 91 Bq m⁻³, respectively. The estimated geometric and arithmetic mean annual radon concentrations that Finnish workers are exposed to were assessed as 19 and 33 Bq m⁻³, respectively. The generic ventilation correction factor for workplaces was calculated as 0.87. Assessed with probabilistic methods, there are approximately 34,000 workers in Finland whose exposure to radon exceeds the reference level of 300 Bq m⁻³. Although radon concentrations are generally low in Finnish workplaces, many workers are exposed to high levels of radon. Radon exposure in the workplace is the most common source of occupational radiation exposure in Finland.

(1) Background: Affordable electronic radon instruments have become increasingly popular as alternatives to traditional home radon measurements, which require a minimum duration of two months. This study aimed to determine how results obtained from these devices should be interpreted and whether short-term measurements lasting 2–5 days can be reliably used to assess the need for radon remediation in buildings, estimate residents’ exposure, or assess public exposure. (2) Methods: A year-long radon measurement was conducted in 55 dwellings, selected to represent the Finnish housing stock as accurately as possible. Radon concentrations were recorded hourly, and the results were analysed using probabilistic analysis to calculate the likelihood of erroneous assessments. (3) Results: If a maximum false-negative rate of 1% is accepted, the action level for a 2–5-day measurement is 90–100 Bq/m³. For measurements exceeding this threshold, a longer measurement period is necessary. (4) Conclusions: Based on this study, short-term radon measurements cannot yet be recommended as a replacement for current methods. However, the study revealed significant radon level fluctuations in September, suggesting that this period should be reconsidered for inclusion in the measurement season.