Various factors that affect the rate of radon entry were investigated in tw
o detached hill-side houses. In the slab-on-grade house (A), this rate reac
hed its maximum value during a particular weather condition when the wind-i
nduced internal transport of radon, whereas the rate of radon entry into th
e basement house (B) on the upper slope of a esker was highest when the win
d was blowing towards the esker. In neither house did changes in barometric
pressure measured at 3 It intervals influence the radon entry rate. Nor di
d rain influence the rate of radon entry into house A. In house A, the rado
n entry rate was observed to have a 2-3 h delay: and after it was adjusted
by the analysis of covariance, the radon entry rate was higher in the morni
ng and lower in the evening. In house B, however, diurnal variations in the
radon entry rate were negligible. (C) 2001 Elsevier Science Ltd. All right
s reserved.