Radon (Rn 222) is a significant contributor to natural radiation exposure in residential environments such as single-family houses and multistory buildings. This study monitored radon activity concentration (RAC) in 455 apartments in 30 multistory buildings in Buzău, Romania. Integrated measurements of the RAC using CR-39 nuclear track detectors were conducted for a period of 3 to 4 months. The results revealed that the RAC varies between buildings, with an annual average between 33 and 77 Bq/m³. This variation may be attributed to poor ventilation and the chimney effect in common ventilation ducts, which may facilitate radon displacement vertically. Also, apartments with low occupancy or inadequate ventilation showed higher radon levels of up to 285 Bq/m³. The study highlights the potential risk of increased radon exposure in energy-efficient buildings due to poor ventilation, emphasizing the need for special attention to radon mitigation measures in building design. The results emphasize that the RAC is influenced by building characteristics, room use, and ventilation, with significant implications for health risks in urban residential environments.

Due to the higher susceptibility of children to ionizing radiation, it is imperative to evaluate the radon activity concentration (RAC) in educational buildings, conduct additional investigations to identify radon entry routes, and implement remedial measures to minimize exposure to this radioactive gas. In Romania, educational buildings are a category of public buildings where it is mandatory to perform RAC measurements. The present study examines data obtained from 41 Romanian educational buildings, where initial and additional radon investigations were performed. The first objective was to identify the factors influencing the variability of the RAC inside the buildings. The second objective was to emphasize the importance of short-term (a few days), continuous measurements in identifying buildings with RAC exceeding the reference level. High RAC values were associated with the classrooms located on the ground floor of the building compared to the administrative ones. The multiple linear regression led to a coefficient of determination of 0.11, the relative humidity and the amount of precipitation being the main variables with a significant impact, kept in the model, the lack of a significant association between the indoor RAC and the radon potential in the soil being obtained. Comparison of the radon long-term integrated measurements with continuous, short-term, led to the suggestion of three different scenarios for the measurement work protocol. By following the suggested modifications, it is possible to accelerate the procedure in situations where the time needed to plan renovations and radon remedial measures is shorter than the time needed to conduct integrated measurements.

Detailed soil radon measurements were conducted in the eastern Poiana Ruscă Mountains, motivated by the area’s complex geology, varied topography, and previously reported high indoor radon levels that pose a health risk to local residents. A total of 110 locations were investigated by conducting 330 measurements over a 480 km² area, using the Radon Monitor-2 (RM-2) and Radon-Jok devices, for assessing the radon activity concentration in soil and soil permeability in correlation with local geological formations. The Neznal method was used to derive the GRP, which was categorized into low (<10), medium (10–35), and high (≥35) risk categories. The arithmetic mean radon concentration was 37.5 kBq/m³, with values ranging from 5.1 to 163 kBq/m³. Soil permeability ranged widely across geological formations, from 6.9 × 10⁻¹⁴ to 2.7 × 10⁻¹¹ m². The highest radon concentrations and geogenic radon potential (GRP) values were associated with micaceous schists interlayered with amphibolites and sericitic quartzite schists. The results, comparable to those from previous studies, indicate a medium to high geogenic radon potential in the eastern Poiana Ruscă Mountains, which exposes the inhabitants of Lunca Cernii de Sus and, to a lesser extent, those of Lunca Cernii de Jos to an increased radon risk.