Radon is a naturally occurring radioactive gas, colorless, odorless, and tasteless, that seeps out of soil and rock and can accumulate inside buildings, where it is a leading cause of lung cancer.
What radon is
- Radon is a noble gas (chemical symbol Rn, atomic number 86) produced by the decay of uranium and radium in rocks and soil.
- Although it is heavier than air radon moves up through the ground and can enter structures through cracks in slabs, foundations, crawlspaces, and other openings, pulled upward by stack effect as warm air in the home rises.
Health risk
- Radon is the second leading cause of lung cancer in the U.S. after smoking, responsible for an estimated 21,000 lung cancer deaths per year (EPA).
- Breathing elevated levels over time damages lung tissue; the main concern is long-term exposure, not short, brief spikes.
Radon in homes
- Elevated radon has been found in all 50 states; about 1 in 15 U.S. homes is estimated to have high radon levels.
Testing basics
- You cannot detect radon with your senses; testing is the only way to know a building’s level.
- Common options are: short-term charcoal or digital tests (typically 2–7 days) and long-term tests (90+ days) for a more accurate annual average (levels can vary seasonally).
- Tests are usually placed in the lowest regularly used level of the home (e.g., basement or first floor), away from drafts and exterior walls.
Interpreting results and mitigation
- In the U.S., 4 picocuries per liter (4 pCi/L) is the EPA’s recommended “action level” to fix a home, though mitigation is often recommended starting around 2–4 pCi/L.
- The standard fix is an active soil depressurization system (radon mitigation system) that uses piping and a fan to vent soil gases from below the slab or crawlspace to above the roof.
- Properly designed systems typically reduce radon by 50–99% and are considered a permanent building component requiring periodic fan checks.