Summary of Radon Concentrations in Us Epa New Construction Projects

Soil Depressurization

No. of Barrier Only Passive Active

Project Houses pCi/L pCi/L pCi/L

Source: Adapted from U.S. EPA, Radon-Resistant Construction Techniques for New Residential Construction—Technical Guidance, EPA/625/2-91/032, U.S. Environmental Protection Agency, Washington, DC, February 1991.

radon-laden soil gases move from an area of higher pressure to an area of lower pressure. Most buildings tend to maintain themselves at an air pressure lower than the surrounding soil. This characteristic is due to weather-driven parameters such as indoor/outdoor temperature differences and wind. The use of exhaust fans and combustion devices in a home will also create a negative pressure in the home. If cracks and holes in the foundation are open to the surrounding soil, radon will be drawn into the building. Figure 31.11 illustrates the principle of pressure-transported radon and also shows some of the things that produce the differences in pressure.

FIGURE 31.11 Negative pressure sources in a typical building. (Adapted from U.S. EPA, Radon-Resistant Construction Techniques for New Residential Construction—Technical Guidance, EPA/625/2-91/032, U.S. Environmental Protection Agency, Washington, DC, February 1991.)
FIGURE 31.12 Theory of operation of a SSD system. (Adapted from U.S. EPA, Radon-Resistant Construction Techniques for New Residential Construction—Technical Guidance, EPA/625/2-91/032, U.S. Environmental Protection Agency, Washington, DC, February 1991.)
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