Influence of environmental factors on indoor radon concentration levels in the basement and ground floor of a building - A case study

A series of experiments was conducted to measure indoor radon concentrations variations and observe any correlations with indoor and outdoor atmospheric parameters for over a period of one year. Indoor environmental parameters and radon concentrations were measured on an hourly basis in a two-story building both in a laboratory on the well-ventilated ground floor and in the basement below it which had negligible ventilation. The monthly average indoor radon concentration value of 29 ± 21 Bq m−3 in the laboratory was below the ICRP recommended limit of 200-300 Bq m−3. The monthly normalization factor for that location ranged from 0.5 to 2.0, while the seasonal normalization factor ranged from 0.78 to 2.0. In the unventilated basement, however, the average monthly indoor radon concentration was 1083 ± 6 Bq m−3 with little seasonal variation. The basement is only used for storage and thus the elevated radon concentration does not pose a serious health risk. The results indicated that indoor radon levels are higher in the autumn-winter season than in the spring-summer season. Analysis further showed that indoor radon concentrations negatively correlated with indoor humidity (correlation coefficient R = −0.14, p < 0.01), outdoor temperature (correlation coefficient R = −0.3, p < 0.01), outdoor dew point temperature (correlation coefficient R = −0.17, p < 0.01) and outdoor wind speeds (correlation coefficient R = −0.25, p < 0.05). Radon concentrations correlated positively with outdoor barometric pressure (correlation coefficient R = 0.35, p < 0.01), indoor-outdoor temperature difference (correlation coefficient R = 0.32, p < 0.05) and indoor-outdoor barometric pressure difference (correlation coefficient R = 0.67, p < 0.01). Indoor temperature, indoor barometric pressure and outdoor wind direction showed no clear correlations with indoor radon concentration.