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Authors (affiliation): I. Dimitrova (SU, Bulgaria), K. Mitev (SU, Bulgaria), S. Georgiev (SU, Bulgaria), V. Todorov (SU, Bulgaria), Z. Daraktchieva (UKHSA, UK), C B Howarth (UKHSA, UK), J. M. Wasikiewicz (UKHSA, UK), Benoit Sabot (LNE-LNHB, France).
Recently, affordable and sensitive continuous radon monitors became available at the market. They could open the doors to new approaches for estimation and reduction of the indoor radon exposure. Metrological tests of these monitors are necessary to uncover their full potential and support their wider application.
Metrological tests of 20 RadonEye continuous monitors were performed at Sofia University (SU), Bulgaria and UK Health Security Agency (UKHSA), United Kingdom. Their backgrounds and correction factors to referent activity concentration were determined. The correction factors were estimated by exposure to activity concentration traceable to the primary radon standard at LNHB, France. Two approaches for exposure were compared – several longer sessions with different constant activity concentrations and a single session with continuously increasing activity concentration. It is shown that the two approaches give comparable results.
The correction factors of the 20 monitors in the range in which the RadonEye's response can be considered linear (below 3500 Bq/m3) varied from 0.70 to 1.06. Eight of the monitors were also exposed at LNHB, France to a traceable radon activity concentration of 4702(61) Bq/m3. The correction factors at this level were 15 to 20 % higher than these in the range below 3500 Bq/m3. This was attributed to the non-linearity of the RadonEye response, which has been reported previously. The upper limit of the monitors was tested at Sofia University. It is demonstrated that different monitors saturate at different levels that are significantly below the upper limit of 9435 Bq/m3 declared by the producer.
The background of the monitors was determined by exposure in a nitrogen atmosphere for about ten days. The estimated background values for 1-hour-long measurements were below 3.5 Bq/m3 for all monitors. This shows that the monitors are sensitive enough for indoor radon measurements.
The results demonstrate that these monitors should be calibrated at radon activity concentrations close to the typical values observed in buildings and below 3500 Bq/m3. The exposure can be carried out in a single exposure session at changing activity concentration. Data from the conducted exposures and from ongoing measurements in buildings is presented. It is shown that RadonEye monitors follow promptly (with an effective time of about 90 minutes) the changes in the radon activity concentration. This indicates that they can be used for exploration of new approaches for estimation of the radon exposure in homes and workplaces.
