Real time monitoring of Rn-222 in workplaces and estimation of working time correction factor

The potential of electronic monitors for evaluating radon exposure is still not fully harnessed, and tests under real conditions are scarce. Ten workplaces were continuously monitored for a year with the radon measurement network of Sofia University, with calibrated and metrologically assured RadonEye +2 monitors. In 7 of the workplaces the average activity concentration of radon during the working time was significantly lower than the total time average. This difference is attributed to behavioral patterns. The ratio of the working time and the total time average (called working time correction factor k WT ) for the whole year ranged from 0.71 to 0.98. Its weekly values varied significantly with coefficients of variation between 9 and 28%. Therefore, using short term estimates of k WT to correct the total time radon average determined by passive detectors could lead to bias. The workplaces also exhibited different seasonal radon patterns, although most were offices with similar schedules. In most pairs of workplaces the monthly averages were correlated very weakly or even negatively. This indicates that seasonal radon variations could be specific to each workplace. The value of k WT also varied with the season, suggesting that seasonal variations of radon during working hours might differ from those observed with passive integrating detectors. Overall, long-term follow-up by metrologically assured electronic monitors could help to improve and personalize the estimate of radon exposure of workers. These monitors could potentially support smart anti-radon systems with optimal operation schedules, thereby contributing to the reduction of the energy impact of buildings. • Electronic radon monitors offer better and tailored estimate of exposure at work • In 10 workplaces working time to total time radon ratio was between 0.71 and 0.98 • Working time radon correction found for one-week or one-season can be biased • Seasonal radon variations inside and outside working hours can differ significantly • Monthly radon fluctuations can be badly correlated even in similar workplaces