Evaluating radon concentration and temporal correction factors in residential and workplace buildings: A comparison of passive and active methods

Effective mitigation of the health impacts of radon exposure begins with accurate measurement of this environmental contaminant. Typically, radon surveys require measurements over a period of several months. This process involves the application of temporal correction factors (TCF). Disparities in indoor radon concentration (IRC) are evident across building types. While the integrated technique has traditionally been considered the most reliable for measuring IRC, the active method is becoming more prevalent due to the availability of commercial radon measurement instruments. The aim of this study is to compare IRC using passive (CR-39) and active (ICA device) methods across 69 indoor spaces, including 35 workplaces and 34 residential buildings. The investigation was conducted over a span of one year and included 966 CR-39 detectors that were replaced every 3 and 6 months, respectively, to assess seasonal fluctuations and facilitate the computation of TCF. Statistically significant differences in IRC were observed between residential and workplace buildings (p < 0.001). Among workplaces, educational and research institutions showed the highest average IRC (166 Bq/m³), while hospitals exhibited the lowest (25 Bq/m³). Significant differences in TCF were found between the two measurement methods (p < 0.05), making TCF specific to the passive method inapplicable to active method. Moreover, distinctions between workplace and residential buildings, including the presence of air conditioning units and differing occupancy patterns, lead to substantial differences in both IRC (p < 0.001) and TCF. The assessment of radon exposure based on room occupancy duration revealed substantial variations: workplaces showed lower actual exposure (62 Bq/m³ vs. 75 Bq/m³, p < 0.001), while residential settings, particularly at night, displayed higher exposure (278 Bq/m³ vs. 245 Bq/m³, p = 0.02) than integrated measurements suggest. Continuous monitoring systems offer critical insights into true radon exposure levels.