When people think about home inspections, they often focus on the roof, the foundation, or whether the HVAC system needs replacing. But one of the most serious hazards a home can contain can't be seen, smelled, or tasted.
Radon is an invisible radioactive gas that naturally occurs in soil and rock. According to the Environmental Protection Agency, radon is the second-leading cause of lung cancer behind smoking and the leading cause among non-smokers. Yet many buyers know little about it, and radon testing is not automatically included in most home inspections.
On a recent episode of the Real Estate Update podcast, Ron Rupp, better known as "Radon Ron KC," explained why radon testing is one of the most overlooked aspects of homeownership.
"It's almost like voodoo magic," Rupp said. "You can't see it, can't smell it."
Fortunately, radon is easy to test for and, in most cases, relatively straightforward to fix.
What Is Radon?
Radon is a naturally occurring radioactive gas created by the breakdown of uranium and radium in soil and rock. As the gas rises from the ground, it can enter homes through cracks in foundations, crawl spaces, sump pits, and other openings.
A few key terms help explain the basics:
- Radon: A colorless, odorless radioactive gas that forms naturally in the ground and can accumulate inside homes.
- Radon Mitigation System: A system designed to vent radon gas from beneath a home and safely disperse it outside.
- Picocuries Per Liter (pCi/L): The standard unit used to measure radon concentration inside a home.
Because radon exposure occurs gradually over many years, homeowners may never realize there is a problem until serious health consequences develop.
Why Modern Homes Can Trap More Radon
Many people assume older homes are more vulnerable to environmental hazards. In the case of radon, though, newer and more energy-efficient homes can sometimes experience more elevated levels.
According to Rupp, homes naturally exchange air with the outdoors through a process known as the stack effect.
As heating and cooling systems operate and outside conditions change, air pressure differences cause homes to pull air upward and out. Replacement air must come from somewhere, and much of it enters through the lowest level of the house.
Because modern homes are more tightly sealed than older homes, radon gas entering from beneath the structure may remain trapped inside longer.
That doesn't mean new homes are more dangerous. It simply means no home should be assumed safe without testing.
Radon Isn't Just a Basement Problem
One of the most common misconceptions about radon is that only basements need to be tested.
Rupp said that belief goes back decades.
"We tell people to test the lowest level of your house," he said.
That's because not every home has a basement. Slab foundations and crawl spaces can also allow radon gas to enter.
The proper location for testing depends on how the home is designed. If the property has a basement, that’s still the best place to test. In homes without basements, the lowest occupied level is generally the most appropriate place for a test.
Radon Exists Almost Everywhere
Many people believe radon is a problem confined to certain parts of the country. While some regions have higher concentrations than others, radon can be found almost anywhere.
"Both," Rupp said when asked whether radon is concentrated in certain areas or widespread throughout the country.
The EPA's radon maps classify regions based on average levels, but those maps have limitations. Areas showing lower risk may simply have less testing data.
According to Rupp, the absence of red on a map doesn't mean an area is free of radon.
"I would still test," he said.
Hot spots can exist even within the same city. One community may have relatively low readings, while another neighborhood just a few miles away could have much higher concentrations.
Because radon comes from the geology beneath individual homes, testing remains the only way to know whether a specific property has elevated levels.
Understanding Radon Measurements
Radon concentrations are measured in picocuries per liter, or pCi/L.
A few important benchmarks include:
- Below 2 pCi/L: Considered relatively low risk, though no level of radon exposure is completely risk-free.
- Between 2 and 4 pCi/L: The EPA recommends homeowners consider mitigation to reduce long-term risks.
- Above 4 pCi/L: The EPA recommends implementing a mitigation system to lower radon levels.
Rupp explained that many homeowners are surprised when they receive results showing six or eight pCi/L because they have no symptoms and had never considered radon before.
"Four is equal to eight cigarettes a day of continuous exposure," he said. A reading of eight is like smoking nearly a full pack.
Smoking and radon exposure together create an even greater health risk. According to the EPA, smokers exposed to elevated radon levels face significantly higher rates of lung cancer than non-smokers.
Is Radon Testing Included in a Home Inspection?
Many buyers assume radon testing is automatically part of a standard home inspection.
It usually isn't. According to Rupp, you need to ask for it specifically. Plus, not all home inspectors may be licensed or certified to test for radon, which is where professionals like Radon Ron KC come in.
For homeowners, however, testing can be performed in several ways:
- Short-term test kits available at home improvement stores
- Long-term test kits evaluated by a lab
- Digital radon monitors
- Professional radon inspections
Most home test kits cost around $15 to $30, while professional testing generally costs more but may provide greater accuracy and documentation for real estate transactions.
For buyers, requesting a radon test during the inspection contingency period can provide valuable information before being locked into the purchase.
Elevated Radon Doesn't Mean You Should Walk Away
Learning that a home has high radon levels can sound alarming, but experts emphasize that elevated readings are not necessarily deal-breakers.
"Don't freak out and go, 'I don't want to buy this house because it has radon,'" Rupp said.
Unlike foundation issues or structural defects, radon can typically be mitigated easily and relatively cheaply.
"If you like the house, just buy the house," he added.
In many transactions, buyers and sellers negotiate who will pay for mitigation. Some sellers agree to install a system before closing, while others may provide credits toward the cost.
The presence of radon is often viewed similarly to a roof repair or HVAC replacement: an issue to address rather than a reason to abandon the purchase.
How Radon Mitigation Systems Work
Fortunately, fixing elevated radon levels is relatively straightforward.
Rupp explained that mitigation systems work by creating a pathway that draws gases from beneath the home and vents them safely above the roofline.
A typical system includes:
- A suction point beneath the foundation
- PVC vent piping
- A continuously operating fan
- A discharge point above the home
The fan creates negative pressure beneath the structure and prevents radon gas from entering living spaces.
"What we're doing is basically sucking all the nasty air out from underneath the house," Rupp explained.
Once released outdoors, the gas quickly disperses and becomes essentially harmless due to dilution in the atmosphere.
Mitigation systems can often reduce radon levels dramatically and are considered highly effective.
How Often Should Homeowners Test?
Testing once isn't necessarily enough.
"Every two years the EPA says you should test," Rupp said. He also recommends additional testing whenever major changes are made to the home.
This can include after:
- Installing new windows
- Replacing HVAC equipment
- Remodeling a basement
- Finishing previously unfinished spaces
- Making significant energy-efficiency upgrades
Changes to airflow patterns inside a home can affect radon levels. However, because testing has become inexpensive and accessible, regular monitoring is easier than ever.
Digital monitors now allow homeowners to continuously monitor radon levels and even view results through smartphone apps.
Why Radon Awareness Matters for First-Time Buyers
First-time buyers often focus on visible issues during the home search. Cosmetic upgrades, kitchens, flooring, and paint colors tend to attract far more attention than indoor air quality.
But environmental hazards can have far greater long-term consequences.
Understanding a few key principles can help buyers approach radon rationally:
- Every home should be tested, regardless of age or location.
- Elevated radon levels are common and fixable.
- Mitigation systems are effective and widely available.
- High readings should lead to negotiations, not panic.
Knowledge about radon – and the options for remedying it – allows buyers to make informed decisions rather than emotional ones.
The Bottom Line
Radon may be invisible, but it is far from rare. Because it cannot be seen, smelled, or tasted, testing remains the only way to know whether elevated levels are present.
Fortunately, finding radon doesn't mean a home is unsafe or should be avoided. In most cases, mitigation systems can reduce exposure effectively, allowing buyers to move forward with confidence.
Many of the insights in this article were discussed by Ron Rupp during his appearance on the Real Estate Update podcast. His message to buyers is simple: always test, but don't let elevated readings scare you away from a home you love.
"Always test," Rupp said. "And always know it can be taken care of."
For most buyers, a radon problem isn't a deal-breaker. It's simply another item on the checklist of responsible homeownership.
