SHORT-TERM AND LONG-TERM INDOOR RADON MEASUREMENTS AND INTERVALS OF HEAVY RAINFALL

The concentration of indoor radon in most homes is increased when home windows and doors are closed. A modest vacuum quickly forms in the attic as the attic air gets hot (compared to outside), expandsw, and flows out through vents common to most attics. The concentration of indoor radon also increases during prolonged radnfall intervals. Most of the radon (a radioactive inert gas) in the soil around the home normally escapes up and out of the soil, and is not pulled into the home. During a prolonged rainfall interval, the upper few cm of the soil becomes water saturated, proventing the normal escape of radon, and increasing the concentration of radon in the soil. In many communities, windows are rarely opened. Outside air is kept out because winter air is too cold, spring air is rich in pollen, summer air is too hot, and fall air is rich in dust. Consequently, in these communities indoor radon is less affected by the outside air temperature as it is the outside precipitation. In our two-year study of almost 2000 homes in Virginia and Maryland, the amount of indoor radon is correlated with the amount of seasonal precipitation, and not seasonal temperature.