Advanced Physical Research

This study investigates the radioactivity of radon gas (²²²Rn) and its exhalation behavior from both imported and local coal samples used in Kirkuk City, Iraq. Coal is known to contain naturally occurring radioactive materials (NORM), including uranium (²³⁸U), thorium (²³²Th), and their decay products, which can pose radiological health risks during storage and combustion. Using CR-39 solid-state nuclear track detectors over a 60-day exposure period, radon concentrations were assessed in coal samples before and after combustion, with both surface (𝐸𝐴) and bulk exhalation rates (𝐸𝑀) rigorously determined. The findings showed that radon concentrations in the air prior to combustion varied from 55 to 80 Bq•m^-3 suggesting that the main source of indoor radon is raw coal. On the other hand, post-combustion concentrations in coal residues were roughly two orders of magnitude higher, rising sharply to 3800–9300 Bq·m^-3. After combustion, radon concentrations in the surrounding air ranged from 45 to 100 Bq·m^-3, within WHO standards but potentially dangerous in poorly ventilated areas. Additionally, compared to pre-combustion values (2.5-3.8 mBq·m^-2·h^-1), surface exhalation rates increased after combustion (1.5-4.5 mBq·m^-2·h^-1), suggesting greater radon release as a result of structural breakdown and radioactive concentration in ash. Additionally, mass exhalation rates increased dramatically, from (0.2-0.7 mBq·m^-2·h^-1·kg^-1)  prior to combustion to (0.4-2.8 mBq·m^-2·h^-1·kg^-1) following. While the link with mass exhalation rates was limited (R²≈0.30), a strong linear correlation (R²=1) was observed between air radon concentration and surface exhalation rates, highlighting the prominent role of surface features in radon emission. In summary, this research emphasizes the substantial increase in radon emission potential from coal combustion, underscoring the need for adequate ventilation, responsible ash management practices, and ongoing radiological monitoring to minimize exposure risks in both professional and domestic environments.