Measuring the real radon exhalation from walls in buildings

• Radon exhalation measured on-site best describes building materials contribution. • The first innovative apparatus to measure the radon exhalation on-site is described it. • The setup is standalone, transportable, and it allows non-destructive measurements. • All technical projects and algorithms are made available at online repository. • The setup improves the specificity, so the effectiveness, of remedial interventions. Building materials may significantly contribute to indoor radon activity concentration. Measuring the radon exhalation rate directly on the existing building elements represents the most accurate and reliable method to assess the building materials’ contribution. However, due to the method’s inner difficulties, no specific apparatus has been developed and documented in the literature. An innovative apparatus has been designed, constructed, and commissioned to measure the radon exhalation rate in situ from vertical surfaces of existing building walls. The apparatus is non-destructive, completely self-standing, and easily transportable. The sealing mechanism has been demonstrated to assure airtightness similarly to destructive setups. The measurements’ repeatability is less than 10% at different radon exhalation rates. The apparatus introduced is the only available solution to measure the site-dependent contribution of building materials to the indoor radon concentration. The apparatus allows for improving the specificity, so the effectiveness, of the remedial interventions to reduce the radon-related health risk.