Radon is a naturally occurring radioactive gas that forms from the decay of uranium in soil and rock, moves upward through the ground, and enters homes through foundation cracks, construction joints, and gaps around service penetrations. It’s colorless, odorless, and completely undetectable without testing. The EPA estimates that radon is responsible for approximately 21,000 lung cancer deaths annually in the United States, making it the second leading cause of lung cancer after smoking. For buyers and sellers alike, radon testing provides one piece of information that no visual inspection, disclosure form, or amount of due diligence can replace.
How Radon Testing Works
Radon testing conducted by a professional home inspector during a real estate transaction follows established protocols designed to produce accurate, defensible results that both parties can rely on. The most common method is a short-term test using a continuous electronic monitor placed in the lowest livable area of the home, typically the basement or lowest finished level, for a minimum of 48 hours under closed-house conditions. Closed-house conditions, windows and doors kept closed except for normal entry and exit during the test period, ensure the test measures the home’s actual radon concentration rather than a diluted reading from open ventilation. The inspector ensures these conditions are established correctly, monitors for any interference that could affect results, and provides a documented report with the measured radon level. Testing conducted under proper protocol by a certified professional carries significantly more evidentiary weight in a transaction than informally conducted testing.
Results That Trigger Mitigation
The EPA’s action level for radon is 4 picocuries per liter of air. A radon testing result at or above this threshold becomes a documented finding that typically prompts negotiation between buyer and seller over who bears the cost of mitigation and whether the system is installed before or after closing. Radon mitigation in most residential applications involves sub-slab depressurization. This system draws radon from beneath the foundation slab and exhausts it above the roofline through a pipe and fan assembly. This system reduces radon concentrations by an average of more than 99 percent in most installations. The mitigation system is installed by a certified contractor, and post-mitigation radon testing confirms the result has been brought below the action level.
What Radon Testing During a Home Sale Means for Buyers and Sellers
For buyers, radon testing is the due diligence step that provides documented knowledge of an invisible condition that would otherwise be entirely unknown. A buyer who purchases without radon testing has no way of knowing. For sellers, proactive radon testing before listing most effectively removes radon as a transaction complication. A seller who has already tested, mitigated if necessary, and can provide documented results and system documentation has converted a potential contingency issue into a disclosed, resolved condition. Buyers who see documented radon testing results, particularly showing a mitigated system and a post-mitigation test below the action level, can make an informed offer without radon uncertainty factored into their negotiating position.
Frequently Asked Questions (FAQs)
Is radon testing required in a home sale?
Radon testing is not universally required by law in most states, but it is strongly recommended by real estate professionals, public health agencies, and the EPA. Some lenders may require radon testing in areas with known elevated radon potential. Even where not required, the health implications of elevated radon and the availability of effective mitigation make testing a straightforward decision for any transaction involving an existing home.
What radon level is considered safe?
The EPA sets its action level at 4 picocuries per liter. The EPA also notes that levels below 4 pCi/L still carry some risk and recommends considering mitigation for levels between 2 and 4 pCi/L. There is no level of radon exposure that carries zero risk; the action level represents the threshold at which the risk is considered significant enough to warrant the investment in mitigation.
How long does radon testing take during a real estate transaction?
A standard short-term radon test takes a minimum of 48 hours under closed-house conditions. Results are typically available within 24 hours of retrieval for electronic monitors or within a few days for laboratory-analyzed charcoal canisters. The testing period is usually coordinated to occur concurrently with or immediately following the general home inspection to minimize the total time required for due diligence.
What does radon mitigation cost and who pays for it?
Radon mitigation system installation costs vary by the home’s construction type, foundation configuration, and the local contractor market. Sellers may pay for installation before closing, offer a credit toward the buyer’s mitigation costs, or negotiate a combination. In most cases the parties reach an agreement because mitigation is effective and relatively affordable.
Does a home with a radon mitigation system already installed need to be tested?
Yes, the presence of a mitigation system confirms that elevated radon was identified and addressed at some point, but it doesn’t confirm the system is currently functioning correctly or that the current level is below the action threshold. Mitigation fans can fail, and changes to the home’s foundation could affect system performance over time. Radon testing in a home with an existing mitigation system verifies current performance and provides the documented result buyers need to confirm the system is protecting the home effectively.
AWP Home Inspections provides buyer’s home inspections and radon testing in West Central and Central Indiana. Contact us to request our services.