How did wind affect the radon entry into seven detached houses

The wind speed and wind direction affected concentration of indoor radon in seven houses, which arelocated in three region of southern Finland. In the case of houses (B - F) which are built on upperslope of a permeable esker, according to the analysis of covariance the highest concentration of indoorradon, 20 - 33% over grand mean, was observed when wind (v?0.4 m.s-1) direction was perpendicularthe esker, leading to increasing pressure of soil gas and consequently to increased radon entry andconcentration. In the same houses the lowest concentration of indoor radon, 22 - 44% under grandmean, was observed when the wind was blowing parallel from the top of the esker. In the slab-ongradehouse (A), these factors have unimportant effect on because the house is located on a gentlysloping rocky surface. Thus, movement of the wind through the top soil generally has only a limitedeffect on pressure conditions in the soil. In this house, the concentration of indoor radon was highest,19% over grand mean, in windy conditions when the wind probably induced transport of containingradon air from the non-ventilated room to the ventilated living space. In the crawl-space house (G),which was built on flat and clayey field, wind speed was not found to influence the concentration ofindoor radon although the radon concentration was higher, 12% over grand mean, in the crawl spacewhen the wind came from shielded directions. In addition, the lowest concentration of radon in thecrawl space, 13% under grand mean, was observed when the wind blew from unshielded directions.Radon concentration in soil in vicinity of the house probably decreased during these wind directions.Wind speed affected only slightly the mean value of concentration of radon in these seven housesbecause radon concentration in the groups of the wind speed did not differ from each other. This studyshowed that the effect of the wind speed on the concentration of indoor radon was difficult to foreseebecause the effect of the wind depended strongly on wind direction