DIRECT MEASUREMENTS OF SOIL-GAS ENTRY INTO AN EXPERIMENTAL BASEMENT DRIVEN BY ATMOSPHERIC-PRESSURE FLUCTUATIONS

To study the importance of changes in atmospheric pressure on radon en try into houses, we have simultaneously measured the soil-gas entry in to an experimental basement structure and the fluctuations in atmosphe ric pressure. Small amplitude (similar to 10 Pa), rapid (similar to 20 min) fluctuations in atmospheric pressure were an important driving f orce for soil-gas entry because 1) the characteristic time for the pro pagation of a pressure disturbance in the soil gas was similar to 2 mi n, and 2) the time-rate-of-change of these small fluctuations is often larger than that of the semi-diurnal oscillations. An analytical mode l has been derived for a structure with a subslab gravel layer based o n a one-dimensional solution to the transient pressure diffusion equat ion. This model correctly predicts the temporal response of the measur ed soil-gas entry into the experimental structure , but underpredicts the amplitude.