Which soil gases are known to affect indoor air quality?

• A. Oxygen and nitrogen
• B. Helium and neon
• C. Water vapor and carbon dioxide
• D. Radon, leakage from underground fuel tanks, pesticides

Answer: (D)

Soil gases can migrate from the ground into buildings and affect indoor air quality. Radon is a naturally occurring radioactive gas formed from uranium in soil and rock; it can seep through foundations and accumulate indoors, posing serious cancer risk with long-term exposure. Vapors from leaks in underground fuel tanks and pesticides in soil can also move upward into living spaces, bringing contaminants with them. These substances originate in the soil and enter indoor air through cracks, joints, and soil-related pathways, making them classic soil-origin IAQ concerns. While water vapor and carbon dioxide, and the balance of oxygen and nitrogen, influence comfort and overall air quality, they are not the soil-origin contaminants that this item highlights.