PSI - Issue 22

6

António Curado et al. / Procedia Structural Integrity 22 (2019) 386–392 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Results presented in Table 1 allow concluding that the parameter Indoor Effective Dose (IED) is almost four times higher than the limit recommended by the International Commission on Radiological Protection (ICRP) for the public dose concerning radiation exposure (1 mSv a year). In fact, the value of 1 mSV/year corresponds to an Average Radon Concentration (ARC) of 180 Bq.m -3 , obtained considering the Office Occupation Schedule (OOC) according to Section 1, i.e. a total of 1540 hours a year of occupancy, which corresponds to a period of 11 months of work, 5 days a week, during 7 hours a day. This approach is known as the dosimetric approach, in line with the methodology prescribed by UNSCEAR. When considering the threshold imposed by Portuguese legislation (300 Bq.m -3 ), the indoor radon concentration is about two times higher than the advised limit. The results show an inconsistency between both approaches — the dosimetric and the regulatory. This discrepancy exists given the regulatory approach ignores the effect of the variable occupancy, on the evaluation of radon risk exposure. On the other hand, the dosimetric approach suggested by UNSCEAR correlates radon risk to the period of exposure and the number of occupants. In fact, an increased risk is observed in rooms that gather a larger number of people during longer periods. The implementation of remediation measures in the office room is mandatory, involving ventilation actions to reduce radon levels and promote a better Indoor Air Quality (IAQ). 6. Conclusion An administrative building made with granite stonework and founded over granite rocks, located in an inner city of Minho region, North of Portugal, was extensively assessed to characterize indoor radon concentration, air temperature and relative humidity in two strategically selected office rooms (a ground-floor and a top-floor room). A ground floor office room extensively occupied was taken for radon risk analysis showing hazard concerning occupants´ radon gas exposure. The experimental assessment was based upon short-term measurements of one complete week over both seasons (winter and summer) to assess indoor radon concentration, air temperature, and relative humidity. The main results of the research are the following:  The radon concentration is above the Portuguese legal limit of 300 Bq.m -3 and the radon risk exposure largely exceeds the limit recommended by the International Commission on Radiological Protection (ICRP) for the public concerning radiation exposure (1 mSv/year).  This research doesn´t consider the cumulative effect regarding radon exposure. Most part of the workers live in dwellings located in areas with granite soils. Therefore, besides the risk exposure in the working place, there is an additional risk that should be added due to the exposure in the residential houses. In light of this, besides mitigation strategies some awareness-raising activities should be organized amid office the administrative building workers and occupants.  This research doesn't consider the cumulative effect regarding radon exposure. Most part of the workers live in dwellings located in areas with granite soils. Therefore, besides the risk exposure in the working place, there is an additional risk that should be added due to the high exposure in the residential houses, as previously studied by Curado et al. (2017) and Lopes et al. (2018). In light of this, besides mitigation strategies some awareness-raising activities should be organized amid office the administrative building workers and occupants. The results of this research recommend not only the implementation of some particular remediation actions, but also the establishing of a long-term characterization for instrumented office rooms. Acknowledgements This contribution has been developed in the framework of the Project “RnMonitor — Online Monitoring Infrastructure and Active Mitigation Strategies for Indoor Radon Gas in Public Buildings on the Northern Region of