Monthly and quarterly correction factors for determining the mean annual radon concentration in the atmosphere of underground workplaces in Poland.

The aimed of the work was estimated the value (level) of mean annual Rn activity concentration in an underground space based on monthly (k) and quarterly (k) correction factors. The calculations of factors were developed with the assumption that measurements will be conducted for at least 1 month or a quarter of a year. Radon monitoring to confirm the calculated values was carried out continuously from 2008 to 2019 and verification was made on real data obtained in 2020. The estimated mean annual Rn activity concentration for spaces with natural air exchange depends on factors k and for mechanically ventilated spaces-k. The k for the first group varies from 1.2 to 3.3 between January and March, and between October and December. In the remaining months, k assumes the values from 0.6 to 0.8. In spaces where natural air exchange with the atmosphere is not impeded by airlocks, the k takes the values of 1.0-1.5 (I-III and X-XII), 0.7-0.8 (V-IX), and 1.0 (IV). For spaces with mechanical ventilation, the k is characterized by values in the range of 1.3-1.4 (I and IV quarter), and 0.9 in the others. In spaces with an unknown ventilation method or when the methods are mixed, the averages for both groups of correction factors can be used: k in the range of ≥ 1.0-1.6 (I-III and IX-XII) and < 1.0-0.7 (IV-XI), and k-in the range of 1.3-1.4 (I and IV quarter) and 0.9 in the others.