Intercomparison on the measurement of the thoron exhalation rate from building materials

Highlights: • The intercomparison on thoron exhalation demonstrated considerable variation. • A harmonized standard for determining the thoron exhalation would be much welcomed. • Suggestions for a harmonized determination of the thoron exhalation are provided. Thoron (²²⁰Rn) exhalation from building materials has become increasingly recognized as a potential source for radiation exposure in dwellings. However, contrary to radon (²²²Rn), limited information on thoron exposure is available. As a result no harmonized test procedures for determining thoron exhalation from building materials are available at present. This study is a first interlaboratory comparison of different test methods to determine the thoron exhalation and a pre-step to a harmonized standard. The purpose of this study is to compare the experimental findings from a set of three building materials that are tested, and to identify future challenges in the development of a harmonized standard.