In Situ Measurement of Radon Exhalation Rate of Building Materials with Leakage Compensation

Building materials have become a predominant source of indoor radon in mid- to high-rise buildings, making in situ measurement of radon exhalation rates from building surfaces essential for identifying radon sources and assessing associated risks. Based on practical survey requirements—addressing sealing leakage at chamber edges and ensuring device portability—this study developed an improved in situ measurement method integrated with leakage compensation through theoretical analysis and experimental validation. The method employs an acrylic accumulation chamber and a portable passive radon detector, adopts a 24 h continuous measurement duration, and processes radon concentration data using an exponential fitting approach. Comparative experiments with the activated carbon method demonstrated good consistency between the two methods. Furthermore, small-scale in situ measurements were conducted in the Beijing area, covering diverse building materials (concrete, brick), surface treatments (cement plaster, coating, wallpaper), and structural components (walls, floors). The results, which varied widely from 0.13 ± 0.11 to 28.00 ± 4.87 Bq/m2·h, confirm the reliability and applicability of the method for in situ determination of radon exhalation rates from interior building surfaces.