Why a Radon Test Before Buying a House Matters

A radon test before buying a house can reveal a significant issue that no walk-through, appraisal, or standard home inspection can detect by sight. Radon has no smell, color, or immediate warning signs, yet it can enter a home from the soil beneath it and accumulate indoors. For a buyer making one of life’s largest financial commitments, testing provides information that can shape negotiations, repair planning, and confidence in the property.

Radon results should not create panic. They should create a clear path forward. Elevated radon can usually be reduced through a properly designed mitigation system, but buyers deserve to know about the condition before closing and to understand what a response may involve.

Why Radon Deserves Attention During a Purchase

Radon is a naturally occurring radioactive gas produced as uranium in soil and rock breaks down. It moves through the ground and can enter a building through small openings in a foundation, sump pit, crawlspace, utility penetrations, floor drains, and cracks in concrete. Once inside, it may become concentrated, particularly in lower levels where people spend time.

Long-term exposure to elevated radon is a known health concern and is associated with lung cancer risk. The risk is higher for smokers, but radon is a concern for everyone in the home. Because the gas is invisible and conditions can vary from house to house, assumptions based on a neighborhood, a home’s age, or a clean-looking basement are not enough.

This is particularly relevant across Greater Chicagoland, where radon potential exists in many communities. A neighbor’s low result does not guarantee a low result next door, and an older home is not automatically at greater risk than a newly built one. Foundation design, soil conditions, air movement, weather, and how the home is operated all affect readings.

When to Schedule a Radon Test Before Buying a House

The most practical time for a radon test is during the inspection contingency period. Including the test with the pre-purchase inspection allows enough time to receive results, review them with your inspector and real estate team, and decide how to proceed before contingencies expire.

Do not wait until the final walk-through. A reliable short-term test generally needs at least 48 hours under specified conditions, and the laboratory or monitoring equipment must still process the result. Scheduling early gives everyone room to address findings without creating unnecessary pressure near the closing date.

Testing is useful for nearly every home type, including homes with basements, crawlspaces, slab foundations, and finished lower levels. A house without a basement can still have elevated radon. So can a condominium or townhouse, especially when the unit is on or near the ground level. For upper-floor units, the testing approach may depend on the building layout and the unit’s connection to the ground.

The Right Test Location Matters

A real estate radon test is generally placed in the lowest level of the home that could be regularly occupied. That may be a basement, a lower-level family room, or the main floor of a slab-on-grade home. The device should not be placed in a kitchen, bathroom, laundry room, crawlspace, or an area with unusual drafts, excessive humidity, or direct heat.

Test conditions matter as well. Windows and exterior doors are typically kept closed except for normal entry and exit before and during a short-term test. Heating and cooling systems may operate normally, but whole-house fans and similar equipment can affect air movement and should be handled according to test protocol. A professionally managed test helps ensure the result reflects recognized testing conditions rather than a compromised setup.

What the Numbers Mean

Radon is measured in picocuries per liter of air, written as pCi/L. The U.S. Environmental Protection Agency recommends taking action when a home’s radon level is 4.0 pCi/L or higher. Buyers may also choose to consider mitigation at lower levels, particularly when readings are close to that benchmark or when they want to reduce long-term exposure as much as practical.

The 4.0 pCi/L level is an action guideline, not a dividing line between “safe” and “unsafe.” Radon risk exists on a spectrum. A result below 4.0 pCi/L is generally reassuring, but it does not mean radon is entirely absent. A result above 4.0 pCi/L does not mean the home is unlivable or that the purchase should end. It means the buyer has a condition to evaluate and a practical correction to discuss.

Short-term tests are common in real estate transactions because they fit within contract timelines. They provide a snapshot of radon conditions over a limited period. Long-term tests, which run for more than 90 days, can offer a more complete picture of a home’s annual average but are rarely practical before a scheduled closing. If a short-term result is near the action level, a buyer may choose to discuss follow-up testing, mitigation, or both based on the timing and terms of the transaction.

What Happens if the Result Is Elevated?

An elevated reading is a decision point, not a verdict on the house. In many cases, the solution is an active soil depressurization system. This commonly involves a pipe that draws radon-laden air from beneath the foundation and vents it safely above the roofline, with a fan creating the necessary suction.

The final system design depends on the home. A property with a crawlspace, multiple foundation sections, a sump pit, or a complex finished basement may need a different approach than a simple slab-on-grade home. A qualified mitigation professional should evaluate the conditions and provide a written scope and cost estimate.

Buyers and sellers commonly handle elevated radon results in one of several ways:

• The seller installs a mitigation system before closing and provides documentation and a post-mitigation test result.

• The parties agree to a credit that allows the buyer to arrange the work after closing.

• The purchase price or other contract terms are adjusted to account for the expected expense.

• The buyer accepts the condition as-is after considering the result, the property, and the cost of correction.

The strongest option depends on the transaction. Seller-installed mitigation gives the buyer a corrected condition before taking ownership, but it can require coordination and verification. A credit gives the buyer control over the contractor and schedule, but the buyer assumes responsibility after closing. Clear written terms matter either way, including who will perform the work, what documentation is required, and whether a follow-up test is expected.

Do Not Overlook an Existing Mitigation System

If the home already has a radon mitigation system, that is usually a positive sign that the issue has been addressed. It is not a reason to skip testing. Systems require electricity, fans can fail, seals can deteriorate, and changes to the basement or foundation can affect performance.

During the inspection, look for the visible components: vent piping, a fan, a system label, and a warning device or manometer that indicates pressure. Then test the home to verify that the system is effectively reducing radon. A system that is present but not functioning is different from a system that is installed, operating, and producing acceptable results.

How Radon Testing Fits With the Home Inspection

A home inspection and a radon test serve different but complementary purposes. The inspection evaluates visible and accessible property conditions, such as the roof, structure, electrical system, plumbing, heating, cooling, moisture concerns, and major components. Radon testing measures an environmental condition that cannot be confirmed through visual inspection alone.

Pairing them helps buyers see the full decision picture. For example, a basement with water-management concerns may warrant careful attention to foundation openings and sump components, but moisture findings do not predict the radon level. The test provides the measurement; the inspection provides context about the home’s construction and condition.

New Horizon Inspection approaches these services with the same objective focus used throughout a property evaluation: provide understandable findings, explain what they mean for the investment, and help clients ask the right next questions. The goal is not to make the decision for a buyer. It is to ensure the buyer is not making that decision without critical information.

Questions Buyers Should Ask Before Closing

Ask whether the test was performed under appropriate closed-house conditions and whether the device was placed in the correct area of the home. If the result is elevated, ask what mitigation approach fits the foundation type, whether a licensed or qualified mitigation contractor will perform the work, and how the result will be verified afterward.

Also consider the future use of the lower level. A storage-only basement today may become a playroom, office, bedroom, or workout space later. Testing and addressing radon before those plans take shape is often simpler than revisiting the issue after renovations are complete.

A house can be a strong purchase even when radon is elevated. What matters is having a credible result, a reasonable correction plan, and enough time to make a deliberate decision. That is the value of testing before the keys change hands: it lets you move forward with clearer expectations and greater control over your investment.