We have investigated, using a mathematical model, the temporal variations of air flux within the soil mass surround a basement in the presence of time dependent periodic variations of barometric pressure and a persistent under-pressure at the basement. Our results of transient asir flow show that for a homogeneous soil medium, the effects of barometric fluctuations are most significant in the cases where soil permeability to air is low and the fluctuation frequency is high. In these cases, the barometric fluctuation can greatly enhance the magnitude of fluxes as well as introduce flow direction reversals from sourrounding soil into the basement. These large fluxes with direction revesals have strong implicatins in regard to advective transport of randon. Our results suggest that the transient oscillations have to be accounted for in quantifying radon entry into buildings. In the actual field set up, the transient behavior will be further influenced by soil permeability heterogeneity, by soil mositure variations, and by the effects of multiple periodic components in the barometric pressure fluctuations. ¿ American Geophysical Union 1990