Radon Testing Before Buying a House: What Every Buyer Needs to Know
You are about to make the biggest purchase of your life. Before you close, there is one invisible hazard that could be lurking in your new home: radon. Here is exactly what you need to know about radon testing during a home purchase — what to request, what results mean, and what to do if levels are elevated.
Why Radon Testing Matters in a Home Purchase
Radon is an invisible, odorless radioactive gas that causes approximately 21,000 lung cancer deaths per year in the United States. It is the leading cause of lung cancer among non-smokers. The EPA estimates that 1 in 15 U.S. homes has radon at or above the action level of 4 pCi/L.
You cannot see, smell, or taste radon. The only way to know if a home has dangerous levels is to test. And the time to find out is before you close — not after you have moved in.
Several states require or strongly encourage radon testing during real estate transactions. Illinois requires sellers to provide radon disclosure forms. Pennsylvania requires state-certified professionals for real estate radon testing. Maryland recommends testing but does not mandate it. Regardless of state requirements, the EPA recommends that every homebuyer have a radon test performed as part of the home inspection.
How Radon Testing Works During a Home Purchase
Who arranges the test? Typically the buyer, through their home inspector or a separate radon testing professional. Some home inspectors include radon testing in their standard package; others offer it as an add-on.
What kind of test is used? For real estate transactions, the gold standard is a continuous radon monitor (CRM) placed by a certified professional for 48 hours. CRMs record hourly readings and detect any tampering (such as opening windows). Consumer-grade electronic monitors are NOT accepted for real estate transactions per CRCPD guidelines — only certified professional CRMs or dual charcoal test kits meet the standard.
How long does testing take? The monitor is placed for a minimum of 48 hours under closed-house conditions. Results are typically available the same day the monitor is picked up.
What does it cost? Professional radon testing for real estate transactions costs $150–$250. This is typically paid by the buyer as part of the inspection process. Some inspectors bundle it with the home inspection for a reduced combined rate.
Where is the test placed? In the lowest livable level of the home — typically the basement. If the home has no basement, the ground floor is tested.
Understanding Your Test Results
Below 2 pCi/L: Low risk. No action needed. Proceed with your purchase.
2 to 4 pCi/L: Moderate risk. The EPA suggests considering mitigation. You may want to negotiate mitigation as part of the sale or plan to address it after closing.
4 pCi/L and above: Action recommended. The EPA action level is 4 pCi/L. Most buyers negotiate mitigation before closing. A mitigation system costs $800–$2,000 depending on your area and is typically completed in one day.
Above 8 pCi/L: Strongly recommended. At this level, health risk is significant with long-term exposure. Mitigation should be a condition of closing.
What to Do If the Home Tests High
An elevated radon result is not a reason to walk away from a home. Radon is extremely common and extremely fixable. Here is how to handle it:
1. Request mitigation as a condition of sale. Most purchase contracts allow you to negotiate radon mitigation as part of the inspection contingency. The seller either has the system installed before closing or provides a credit toward the cost.
2. Get a quote. A standard sub-slab depressurization system costs $800–$2,000. Request a free, no-obligation quote from a certified professional to know the exact cost for the specific home.
3. Have the system installed before or after closing. Installation takes 4–8 hours, one day. A post-mitigation test confirms levels have dropped below 4 pCi/L.
4. Monitor ongoing. After mitigation, a continuous radon monitor like the Airthings Corentium Home 2 (~$179, code RADONSAFETY-10OFF) provides ongoing peace of mind.
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Which Test Kit Should You Use?
For real estate transactions, we recommend hiring a certified professional who uses a continuous radon monitor. However, if you want to do a preliminary screening before the formal inspection, a dual charcoal test kit is the appropriate choice.
Our top pick for real estate: The PRO-LAB Dual Real Estate Kit ($30–$35) includes two detectors and lab fees — meeting the EPA recommendation for duplicate testing. See our full radon test kit reviews for all options.
Important: Consumer electronic monitors (Airthings, Ecosense, etc.) are excellent for ongoing home monitoring but are NOT accepted for real estate transactions. Only certified charcoal kits or professional CRMs are valid for home purchases.
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FAQ
Is radon testing required when buying a house? It depends on the state. Illinois requires disclosure forms. Pennsylvania requires certified testers for real estate. The EPA recommends testing in every transaction regardless of state law.
Who pays for radon testing? Typically the buyer, as part of the home inspection process. Cost is $150–$250 for professional testing.
Should I walk away from a house with high radon? No. Radon is common and easily fixable. Mitigation costs $800–$2,000 and takes one day. Negotiate it into the sale.
Can I use a home radon monitor for a real estate test? No. Consumer monitors are not accepted for real estate transactions. You need a certified professional with a CRM or a dual charcoal test kit.
How long does radon testing take? 48 hours minimum under closed-house conditions.
What Happens After I Submit?
A certified radon professional will call you within 15 minutes during business hours. After hours, expect a call by 8:30 AM next business day. One provider only.
Call or text: (240) 397-6515
RadonSafetyGuide.com is an independent resource. We are not a radon mitigation company.