Objective: The main objective was to test the closed radon exhalation methodology, with AlphaGuard radon detector, for different grain sizes of a granite rock sampled from central area of Belo Horizonte and propose experimental methods for its determination. Theoretical Framework: Natural radioactivity accounts for about 80% of the average annual radiation dose humans receive, primarily due to primordial radionuclides in the Earth’s crust. The World Health Organization (WHO) recommends national radon (Rn) exposure mapping programs based on geological studies due to the significant contribution of Rn gas to annual radiation doses. Studies indicate that granitic and metamorphic rocks, black shales, phosphate rocks, and some carbonate rocks are common radon sources. Rn is generated in soil and migrates through soil pores, entering buildings through cracks and openings. Rn transport is influenced by factors like local geology, humidity, and temperature. Method: The study tested radon exhalation from granite samples in center of Belo Horizonte using a proposed method with AlphaGuard in an exhalation circuit. Results and Discussion The studied method proved to be effective with particle sizes up to 16#. For very fine particle sizes, the air flow is hampered and therefore reduces the effectiveness of transporting the radon-filled gas. Research Implications: The implications of this research are discussed, providing insights into radon exhalation method in a closed circuit and its challenges. This study contributes to literature by studing exhalation rate is vital for estimating radiation risk from many kinds of materials and the indoor radon.
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