Understanding Radon—A Homeowner’s Guide to Testing, Safety & Mitigation
Radon is one of the most misunderstood parts of the home inspection process. It’s invisible, silent, and has no smell — which is exactly why knowing the facts is so important. This guide breaks down what radon is, why it exists, how it's measured, what high levels actually mean, and what to do if your home (or the home you're buying) tests high.
What Is Radon?
Radon is a naturally occurring radioactive gas that forms when uranium in the soil breaks down. Because it’s a gas, it moves upward through the ground and can enter homes through even the smallest foundation openings.
You can’t see it or smell it — which is why testing is the only way to know if it’s there.
Why Does Radon Exist?
Uranium is present in nearly all soil and rock. As it decays, radon is released into the earth’s atmosphere. Outdoors, it dissipates and isn’t a problem. Indoors, however, radon can accumulate to unsafe levels.
Factors that influence radon levels:
Soil composition
Home construction type
Foundation condition
Ventilation levels
Nearby rock formations or natural uranium deposits
You can have a low-radon home right next to a high-radon home — which is why testing is house-specific.
How Radon Enters a Home
Radon gas moves upward from the ground. It enters through:
Foundation cracks
Gaps around plumbing
Crawl spaces
Sump pump basins
Floor drains
Well water (less common)
Porous concrete slabs
Basements and crawl spaces are especially vulnerable, but even slab-on-grade homes can have elevated radon levels.
How Radon Is Measured
Radon is measured in picocuries per liter (pCi/L).
0–1.9 pCi/L — Low/typical outdoor levels
2–3.9 pCi/L — Moderate; further testing recommended
4.0 pCi/L or higher — EPA recommends mitigation
A radon test in a real estate transaction typically runs for 48 hours using a continuous radon monitor (CRM). This device tracks hourly readings and provides an average level.
How Radon Testing Works in a Real Estate Transaction
Radon testing is usually an add-on service during a home inspection. Most areas charge between $100 and $150.
The test:
The inspector places a small device in the lowest livable level of the home.
Doors and windows must remain closed (normal entry/exit is fine).
The device runs for 48 hours.
Results are emailed or printed on-site showing the average reading.
If you're not in a real estate transaction, inexpensive DIY kits or professional tests are available.
What High Radon Levels Actually Mean
If a test result is 4.0 pCi/L or higher, the EPA recommends mitigation. This doesn’t mean the home is dangerous to walk into — radon becomes a concern with long-term exposure over years. Many buyers negotiate with the seller to install a mitigation system or offer a credit toward one.
How Radon Mitigation Works
Radon mitigation systems are highly effective — and surprisingly simple. A typical system includes:
A pipe installed through the basement or garage
A fan that pulls radon from beneath the foundation
Ventilation that safely exhausts radon above the roofline
Continuous monitoring via system gauge
Once installed, radon levels typically drop dramatically — often below 2.0 pCi/L. The fan runs continuously but uses roughly the same electricity as a light bulb.
Do You Need to Re-Test?
Yes — radon levels can change over time. Re-test:
Every 2 years
After major renovations
After foundation work
When finishing a basement
After significant HVAC changes
If you have a mitigation system, you should also check the system’s gauge periodically to make sure it’s working.
Does Every Home Have Radon?
Yes — radon is present everywhere, but not every home has high levels. Because levels vary dramatically, testing is the only way to know.
The Good News
Radon is one of the easiest inspection issues to resolve. It’s:
Simple to test
Affordable to fix
Highly effective to mitigate
Common to negotiate in a real estate deal
Radon is a safety issue — but not a deal breaker.
Final Thoughts
Being informed is the best way to protect your family and make confident home decisions. Radon testing has become a standard part of responsible homeownership and modern real estate, and the fix is far simpler than most people expect.
If you have questions about radon testing, mitigation, or how it affects a home purchase, I’m always here to help.
