Radon enters homes primarily by which pathway?

• A. Through open windows
• B. It moves up through the soil and enters homes via the basement or cracks in the foundation and can also be dissolved in groundwater and enter the home through the wall
• C. Through the chimney
• D. Through doors only

Answer: (B)

Radon is a naturally occurring radioactive gas that moves with soil air and tends to seep into buildings where there are openings in the foundation. The main path is soil gas moving upward and entering through the basement or cracks and gaps in the foundation, driven by pressure differences between indoor air and the soil. It can also be present in groundwater and release into indoor air when that water is used, which is another route but usually less significant than soil-gas entry. Open windows or chimneys are not the primary pathways for radon entry.