Should I Get a Radon Test With Home Inspection?
Buyers under contract face a checklist of optional add-ons their inspector offers, and radon testing is near the top of the list. The question “should I get a radon test with home inspection” comes up most often for first-time buyers who are not sure whether it is a genuine safety step or an upsell. The honest answer depends on geography, the home’s construction, and the buyer’s tolerance for an invisible risk, but in much of Colorado the answer leans strongly toward yes. This guide weighs the decision without alarmism and explains how the test fits into a real estate transaction.
Should you get a radon test during a home inspection?
For most buyers, adding a radon test to the home inspection is a reasonable, low-cost step, and in high-radon regions it is close to essential. Radon is a naturally occurring radioactive gas that seeps up from soil into homes, and it is the second-leading cause of lung cancer in the United States according to the U.S. Environmental Protection Agency. You cannot see, smell, or taste it, so testing is the only way to know a home’s level.
The inspection period is the ideal time to test because the buyer still has leverage. If the result is high, the contract often allows negotiation over who pays for mitigation. Bundling the radon test with the inspection also saves a second visit. The decision is less about whether radon exists and more about whether this particular home and region warrant the small added cost, which the broader radon testing resources help buyers weigh.
Why Colorado buyers should pay attention
Geography drives the recommendation. The EPA maps much of Colorado, including the Front Range counties of Denver, Douglas, El Paso, Boulder, and Jefferson, in Zone 1, the highest-risk category, meaning the predicted average indoor radon level exceeds the action threshold. The Colorado Department of Public Health and Environment reports that a large share of homes tested statewide come back at or above the action level.
That does not mean every home is dangerous, but it does mean the prior probability of an elevated reading is high enough that skipping the test is a real gamble. A buyer purchasing along the Front Range who declines a radon test is, statistically, more likely to be the one who discovers a problem after closing, when fixing it comes entirely out of pocket.
How radon testing works during a purchase
During a real estate transaction, inspectors typically use a short-term test that runs 48 hours or more under closed-house conditions, meaning windows and exterior doors stay shut except for normal entry and exit. The test device sits in the lowest livable level of the home, away from drafts, exterior walls, and high humidity, at a height that approximates the breathing zone.
Two main device types appear in real estate testing: continuous radon monitors, which log hourly readings and resist tampering, and passive charcoal or alpha-track kits sent to a lab. Continuous monitors are favored in transactions because they produce a fast, tamper-resistant report. The mechanics mirror what homeowners do on their own, covered in the radon house test guide, with the difference that a transaction test follows stricter protocols so the result holds up in negotiation.
What the numbers mean
Radon is measured in picocuries per liter of air (pCi/L). The EPA recommends taking action to reduce radon when the level reaches 4.0 pCi/L or higher, and it suggests considering action between 2.0 and 4.0 pCi/L because no level is entirely without risk. Outdoor air averages roughly 0.4 pCi/L, so the goal of mitigation is to get indoor levels as close to outdoor levels as practical.
A single short-term result is a snapshot, and radon levels fluctuate with weather, season, and how the house is operated. A result near the threshold may warrant a follow-up long-term test or a second short-term test before deciding. A clearly elevated result, say 8 or 10 pCi/L, is strong evidence that mitigation is warranted regardless of normal fluctuation.
Cost and how it affects negotiation
A radon test added to a home inspection commonly costs in the range of $100 to $200, a small fraction of the transaction. Mitigation, if needed, is more substantial, often running well over a thousand dollars depending on the home; the average cost of a radon mitigation system guide covers the range in detail.
Here is where timing pays off. If a transaction-period test comes back elevated, the buyer can request that the seller install or pay for a mitigation system, or credit the cost at closing, as part of the inspection-objection process. That same conversation about negotiating repairs is covered in the guide to asking for a price reduction after a home inspection. Discovering high radon after closing forfeits that leverage entirely, which is the strongest financial argument for testing during the inspection.
When you might reasonably skip it
There are limited situations where a buyer might decline. If the seller provides a recent, credible radon test from a qualified provider and the result was clearly low, or if a functioning mitigation system is already installed and documented with a post-mitigation test, a fresh test may be optional, though many buyers still verify. In a very low-radon region, the case is weaker than in Colorado.
Even then, the cost is low enough that many buyers test anyway for peace of mind. The decision ultimately balances the home’s documented history, the regional risk, and the buyer’s comfort with uncertainty. For Front Range homes lacking a recent, trustworthy test, the practical recommendation is to test during the inspection window.
Making the decision
The choice comes down to a simple risk-and-cost calculation. The test is inexpensive, the consequence of missing elevated radon is a serious long-term health risk and an out-of-pocket repair, and the inspection period offers negotiating leverage that disappears at closing. In a high-radon state like Colorado, those factors point clearly toward testing. Buyers can coordinate the radon test through their inspector and lean on the wider hiring process resources to confirm their inspector is qualified to run it correctly.
How the test gets scheduled within the inspection window
The logistics are simpler than buyers fear. A continuous radon monitor needs to sit undisturbed for a minimum of 48 hours, so the practical move is to have the inspector deploy the device at the start of the inspection visit and retrieve it two or more days later, or place it a day or two ahead and read it on inspection day. Either way, the radon result and the inspection report can land together, inside the same contractual objection deadline.
That timing is the whole point. Real estate contracts give the buyer a defined period to raise objections based on inspection findings, and a radon result that arrives after that window closes is far harder to act on. Front Range buyers working with a tight due-diligence schedule should tell their inspector at booking that radon is part of the order, so the monitor goes out early enough for the 48-hour run to finish with days to spare. Coordinating the device placement, the closed-house conditions, and the report delivery is exactly the kind of detail a qualified inspector handles routinely.
Closed-house conditions and why they protect the buyer
A transaction-grade radon test only holds up if the house is operated correctly during the measurement. Closed-house conditions mean windows and exterior doors stay shut except for normal entry and exit, beginning at least 12 hours before the test starts and continuing throughout. Heating and cooling run normally, but whole-house fans and window fans that pull in outside air are off, because they dilute the reading and can mask a genuine problem.
This matters in a purchase because a seller, intentionally or not, can skew a result by leaving windows open or running fans. Continuous monitors counter that risk by logging hourly readings and flagging tampering, sudden pressure swings, movement of the device, or a spike of fresh-air dilution, so the inspector can see whether the conditions were honored. A buyer relying on the result to negotiate wants that tamper record, which is one more reason transaction tests favor professional continuous monitors over a passive kit left to chance.
What happens after an elevated result
An elevated reading is not a deal-breaker; it is a negotiating item with a well-understood fix. The standard remedy is an active soil depressurization system, a fan and vent pipe that draws radon from beneath the foundation and exhausts it above the roofline, and its cost is predictable enough that both parties can negotiate from a real number. The buyer can ask the seller to install a system before closing, credit the cost at closing, or adjust the price, options laid out in the guide to the average cost of a radon mitigation system.
If the seller installs the system, a post-mitigation test should confirm levels actually dropped below the action threshold before closing, and the buyer should receive documentation of both the installation and the verifying test. That paper trail protects the buyer and becomes an asset when the home is later resold. Discovering the same problem after closing strips away every one of these options and leaves the new owner paying for the system and the test alone, which is the core financial case for testing during the inspection rather than after.
New construction, mitigated homes, and other special cases
A few scenarios prompt buyers to wonder whether the radon test is redundant, and each deserves a clear answer. Newly built homes are not automatically safe; radon depends on the soil beneath the foundation, and a brand-new house over uranium-bearing ground can test high. Some new Colorado homes include a passive radon system, piping that vents by natural air movement, but passive systems do not always lower levels enough, so a test is what reveals whether a fan needs to be added.
A home that already has an active mitigation system is a different case. Here the buyer should verify the system rather than assume it works: confirm the fan runs, check the manometer, and ideally run a fresh test to prove current levels are below the action threshold. A system that was installed years ago may have a failed fan or may never have been verified after installation. Documentation from the seller, the installation paperwork plus a recent post-mitigation test, strengthens the case for skipping a new test, but in its absence a quick measurement is cheap insurance. The point is consistent across cases: testing confirms the present reality of a specific home rather than relying on assumptions about its age or equipment.
How the radon decision fits the wider inspection budget
Buyers weighing add-ons during the inspection naturally tally the cost, and radon sits among the most defensible line items. At roughly $100 to $200 bundled with the inspection, it is a small fraction of a transaction and trivial against the potential consequences, a serious long-term health risk and an out-of-pocket mitigation bill of well over a thousand dollars if the problem surfaces after closing. Compared with other common add-ons, radon offers a strong ratio of protection to cost in a high-radon state.
The decision also interacts with the home’s specifics. A property with a finished basement used as living space raises the stakes, because that lowest level is exactly where radon concentrates and where occupants spend hours. An older home with a settled foundation and more cracks offers more entry pathways than a tight new build. Weighing the home’s construction, the regional risk, and the modest fee almost always points Front Range buyers toward testing, and coordinating it through a qualified inspector keeps the protocol correct enough that the result holds up if it drives a negotiation.
This guide summarizes EPA and Colorado state health guidance current as of 2026; consult a certified radon professional for testing decisions specific to your home.
References
- EPA radon health risk and action levels — U.S. Environmental Protection Agency
- Colorado radon program and testing guidance — Colorado Department of Public Health and Environment
- Radon and lung health overview — American Lung Association