Radon Testing for Home Buyers: Why It Belongs on Your Inspection Checklist
Why Radon Testing Matters When Buying a Home
Radon is the second leading cause of lung cancer in the US, responsible for about 21,000 deaths annually according to the EPA. It's colorless, odorless, and found in homes across every state. It's also one of the most overlooked items on a home buyer's inspection checklist.
The good news: testing is cheap, fast, and completely standard. The risk comes from skipping it.
A certified inspector walking a buyer through radon test results — including what the numbers mean and what options exist.
What to Request (and When)
Request radon testing during the inspection contingency period. Most purchase agreements allow 7–14 days for all inspections. Radon testing should happen at the same time as the general home inspection.
Ask your real estate agent or inspector for:
- A short-term test (48–96 hours minimum) using a certified lab canister
- Results certified by an NRPP- or NRSB-licensed professional
- Testing on the lowest livable level — basement if one exists and is regularly used
Avoid:
- Seller-provided results from an old test (more than 1–2 years ago, or taken under non-closed-house conditions)
- Electronic "screening" tests without lab certification
- Tests taken during unusual weather events
Understanding the Numbers
The EPA's action level is 4 pCi/L. Here's how to read results:
| Result | What it means |
|---|---|
| Below 2 pCi/L | Low — no action needed |
| 2–4 pCi/L | Moderate — consider mitigation, monitor |
| 4 pCi/L or above | Action level — mitigation recommended before or after purchase |
| 8+ pCi/L | High — mitigation required; negotiate accordingly |
The average US indoor radon level is 1.3 pCi/L. Anything above 4 pCi/L in a home you're about to purchase needs to be addressed.
Negotiating After a High Reading
A high radon test result doesn't have to kill the deal. It's a negotiating point, not a dealbreaker.
Common approaches:
Seller installs mitigation before closing — you get a post-mitigation test and review results before you move in. Most reliable outcome.
Price reduction — seller reduces price by the estimated mitigation cost ($800–$2,500 for most homes). You hire your own contractor after closing.
Seller credit at closing — seller provides a credit toward closing costs in lieu of the mitigation. Similar to option 2 but structured differently in the contract.
Walk away — if the seller refuses to address a high radon result, you're generally entitled to exit under inspection contingency.
Most sellers will negotiate, especially if the buyer provides written quotes from licensed mitigation contractors. A $1,500 mitigation system is a small number in the context of a home purchase.
Radon sensors are placed on the lowest livable level — typically the first floor or basement — during a 48-hour closed-house test.
What If the Home Already Has a Mitigation System?
Existing mitigation systems are a green flag, not a red one. They show the previous owner took radon seriously. Ask for:
- Documentation of the original test results and when the system was installed
- Evidence the system is functioning (check the manometer on the pipe — fluid should show unequal levels)
- A recent post-mitigation test result (within the past 1–2 years)
If the system has no documentation or appears unmaintained, budget for a retest and possibly a fan replacement ($200–$400).
New Construction Isn't Exempt
New homes often come with radon-resistant construction (RRNC) features: passive venting pipes under the slab, sealed penetrations, and vapor barriers. This reduces radon entry but doesn't eliminate it.
RRNC homes should still be tested. If levels are above 4 pCi/L, adding a fan to the existing passive pipe system is a quick, low-cost fix (usually $200–$500 since the pipe infrastructure already exists).
A properly mitigated home with a working radon system is a safe, standard purchase — the system just needs to be verified.
Finding a Certified Radon Inspector for Real Estate Transactions
For real estate purposes, use a certified professional rather than a DIY kit. Third-party certification matters when it's part of a negotiated transaction.
Look for inspectors certified through:
- NRPP (National Radon Proficiency Program)
- NRSB (National Radon Safety Board)
- Your state's radon program (many states have their own certification requirements)
Radon testing is a $20–$200 investment that can save you from an invisible health risk or give you a legitimate negotiating tool at closing. It should be on every home buyer's checklist without exception.