Is Your Home Letting Radon In? Common & Surprising Sources and Prevention Tips
Radon is a naturally occurring radioactive gas, and a serious hidden health risk. You can’t see, smell, or taste it, which is why it’s known as a “silent threat.” Prolonged radon exposure is the second leading cause of lung cancer in the U.S. (and the top cause among non-smokers), contributing to an estimated 21,000 deaths each year, according to the EPA. Elevated radon levels have been found in homes across all 50 states, and even so-called “safe radon levels” still carry risk. That’s why every home should be tested. The good news? With the right tools and strategies, you can detect and reduce radon effectively. In this post, I’ll cover radon sources, debunk radon myths, and explain how to prevent radon in your home, for good.
Radon from Countertops and Natural Building Materials
One surprising source of indoor radon is the building materials inside your home. Granite countertops, concrete, brick, stone, and other mineral-based materials can contain tiny amounts of uranium and thorium. As these naturally radioactive elements decay, they can produce radon gas, which may slowly release into the air.
This might sound alarming, especially if you have granite counters in your kitchen or stone walls, but the actual contribution from most building materials is minimal. According to the U.S. EPA, while some granite may emit low levels of radon, there’s no evidence that standard residential granite countertops significantly increase indoor radon levels.
The same goes for other materials like brick, drywall, or concrete. These may release trace amounts of radon, but not nearly enough to explain high indoor radon levels in most homes. The EPA, CDC, and American Lung Association all agree: the primary source of radon is the soil beneath your home’s foundation, not your kitchen counters.
Radon in the Water Supply (Especially Well Water)
According to the EPA, water typically contributes only about 1–2% of the radon found in indoor air. Still, if your well water contains very high radon levels, it can add enough to push you past recommended limits.
Health-wise, the main concern is inhalation, not ingestion. While drinking radon-rich water may slightly raise cancer risk (e.g., stomach cancer), the far greater risk comes from inhaling radon released from water into indoor air.
What you can do:
Start by testing your indoor air with a radon monitor or test kit.
If levels are high and you use a well, consider testing your water too.
If your well water exceeds safe radon levels, aeration systems (which bubble air through the water before it enters your home) are the most effective fix.
Granular activated carbon (GAC) filters can help at lower levels but may accumulate radioactivity over time.
In most cases, radon from soil is the main concern, but waterborne radon shouldn’t be overlooked, especially if you rely on a private well.
Do Air Purifiers Remove Radon?
When people discover high radon in their homes, a common question is: “Can I use an air purifier to fix it?” Unfortunately, the answer is no, at least not effectively.
Most air purifiers are designed to remove particles, like dust, pollen, or smoke. But radon is a gas, not a particle, and it slips through HEPA filters and even most carbon filters. While activated charcoal can absorb some radon, it would take industrial-scale filtration to make a meaningful difference in home settings.
Some advanced purifiers with thick carbon filters may reduce radon decay products (the radioactive particles radon turns into), but they won’t stop the radon gas itself from entering and accumulating. Even manufacturers of high-end air cleaners acknowledge that air purifiers are not a solution for radon. They may be helpful as a supplement, but should never replace a proper radon mitigation system.
Construction-Related Radon Risks
Home improvement projects and renovations can inadvertently impact your home’s radon levels. Many people are unaware that altering the structure, airflow, or energy efficiency of a house might change how radon enters and accumulates. If you’re planning to remodel or retrofit your home, it’s wise to include radon considerations in the plan (and to test afterward).
Finishing a Basement
An unfinished basement often has cracks and gaps that allow radon in, but also natural ventilation. When you finish a basement, sealing walls and floors and tightening the space can either reduce radon entry or increase it by trapping radon that was previously escaping. Plus, spending more time in a finished basement raises your exposure risk.
HVAC Changes
Updating your HVAC system or changing how your home ventilates can shift pressure dynamics and affect how radon moves. For example, new ductwork or leaky basement returns can pull in more radon, while balanced ventilation (like an ERV) can help push it out. Any major airflow change, like adding a whole-house fan, may alter radon levels. Always retest for radon after HVAC updates to ensure the changes haven’t made things worse.
Energy-Efficiency Upgrades
Insulating and sealing your home reduces energy costs but can also trap radon. Older, drafty homes might have naturally vented radon, but tighter homes retain more of it. The EPA notes that newer, energy-efficient buildings may see higher radon levels without mitigation. Weatherization is still beneficial, just remember to test afterward, especially after sealing up foundations, basements, or crawl spaces.
Radon Entry via Crawl Spaces, Sumps, and Wall Gaps
How, exactly, does radon get into a house? We’ve hinted at it throughout, but let’s zero in on the common entry points, including some you might not suspect. Understanding these can help you target problem spots and better seal or ventilate them.
Cracks and Gaps
Any crack or gap in your foundation can let radon in. The gas naturally moves from high-pressure soil into lower-pressure spaces like basements, seeping through floor cracks, wall joints, and gaps around pipes. Even airtight-looking homes have tiny openings. As the EPA points out, radon only needs one.
Crawl Spaces
Homes with dirt-floor crawl spaces are especially prone to radon. Exposed soil allows radon to rise directly into the home, even if the crawl space is vented. Encapsulating the area with a sealed plastic vapor barrier, and optionally adding a vent pipe or suction system, can reduce radon entry while also improving moisture and insulation.
Sump Pumps and Drainage Systems
Unsealed sump pits and French drains give radon a direct path into your home. To block it, mitigators install airtight covers, often with vent pipes, on sump pits. Small openings around pipes, drains, or support posts can also let radon in, so sealing all gaps is key.
Wall Gaps and Building Materials
Hollow concrete block walls can carry radon through their cores and release it into basements via cracks or unsealed areas. The floor-wall joint—a common, often-cracked seam—runs along the entire perimeter of most basements and is a frequent radon entry point. While building materials like brick and concrete can emit radon, this is usually a minor source compared to soil gas. Still, porous materials contribute, especially in older or poorly sealed foundations.
Common pathways for radon entry into a home. Radon gas (arrows) can seep upward from the soil through basement cracks, crawl spaces, sump pumps, and gaps in foundations, accumulating in living spaces.
Radon Myths and Misconceptions
Radon is subject to quite a few myths and misconceptions. Let’s debunk some of the big ones so you can separate fact from fiction:
“New homes don’t need radon testing.” – False. Even brand-new homes can have high radon levels. While some include Radon Resistant Construction (RRC) features, these don’t guarantee safety. Modern homes are also often tightly sealed, making radon buildup more likely. The Oregon Health Authority notes that homes with RRC “may still have elevated levels of radon” and should be tested after construction.
“We don’t have radon in our area.” – Potentially false. Radon has been found at elevated levels in every U.S. state. Your ZIP code or neighborhood doesn’t predict your risk—radon varies home to home due to soil and construction factors. Testing is the only way to know for sure.
“Homes without basements don’t get radon.” – False. Slab-on-grade and crawl space homes can have high radon too. Radon can enter through cracks in slabs or exposed dirt in crawl spaces. Even homes on stilts can trap radon if they cover enough soil area.
“My neighbor tested low, so I’m sure my house is fine.” – False. Radon levels vary drastically, even between identical homes next door. Your neighbor’s results have no bearing on yours. Test your own home to know your risk.
“Radon testing is hard, expensive, or time-consuming.” – False. Modern radon testing is easy and affordable. DIY radon test kits cost $20–$40 and are available online or in hardware stores. Some state agencies offer free kits. Long-term digital radon monitors and professional testing are also accessible. Testing is quick, affordable, and essential.
Prevention Strategies: How to Prevent Radon in Your Home
If testing reveals elevated radon in your home (or you simply want to be proactive) there are proven strategies to prevent radon from entering or accumulating. Think of it as a two-part approach: keep radon out at the source, and vent any that still gets in. Here are the key prevention and mitigation measures:
Seal Entry Points: Sealing cracks in floors, walls, around pipes, and covering open sumps helps reduce radon entry, but it’s not a standalone solution. For crawl spaces, place and seal a heavy plastic sheet over bare soil. Sealing works best as a first step or in combination with a radon venting system.
Install a Radon Venting System: The most effective solution is an active radon mitigation system: a fan and pipe assembly that draws radon from beneath your foundation and vents it above the roof. This system, often called sub-slab or sub-membrane depressurization, can cut radon levels by up to 99% when installed properly. Costs typically range from $800–$1,500. After installation, always re-test to confirm safe radon levels.
Improve Ventilation (Carefully): Heat Recovery Ventilators (HRVs) or Energy Recovery Ventilators (ERVs) can help dilute indoor radon by exchanging stale indoor air with fresh outdoor air. These are best used alongside other mitigation systems. Simply opening windows can offer short-term relief but isn’t a reliable year-round fix.
Build with Radon Resistance: If constructing a new home or addition, ask your builder about Radon-Resistant New Construction (RRNC). This includes gravel beneath the slab, a sealed plastic barrier, and a passive vent pipe, often for little extra cost. These features can drastically reduce radon risks from the start.
Maintain and Retest: Radon levels can change over time. Check that your system’s fan is running (look for a manometer or alarm) and re-test every few years or after events like earthquakes or foundation work. A reliable radon monitor makes this easy.
When it comes to reducing radon, professional guidance is invaluable. A certified radon mitigation contractor can assess your home’s layout, radon entry points, and airflow dynamics to recommend the most effective strategy. According to both the American Lung Association and EPA, a well-designed radon mitigation system can reduce even very high radon levels to below the recommended action level. Many homeowners achieve safe radon levels after mitigation. It's a one-time project that delivers long-term peace of mind.
With the right fixes in place, your indoor radon levels can return to background levels found outdoors, typically under 0.5 pCi/L. That’s the ideal: clean, breathable indoor air that poses little to no risk. And remember, you’re not alone in this. Homeowners across the country are learning how to prevent radon, installing radon monitors, and securing their homes for the future. It all starts with one simple step: testing.
For more detailed guidance on choosing the right detection kit or monitor, check out my Doctor’s Guide to Home Radon Detection Kits, which provides an in-depth look at radon monitors and how to use them effectively in your home.
Sources:
U.S. Environmental Protection Agency (EPA)
General Radon Information: https://www.epa.gov/radon
Radon in Granite: https://www.epa.gov/radon/radon-granite-countertops
Radon in Water: https://www.epa.gov/radon/radon-water-health-risk-indicator
Radon Reduction Techniques: https://www.epa.gov/radon/radon-reduction-techniques-consumers-guide
Radon and New Homes: https://www.epa.gov/radon/building-new-home-have-you-considered-radon
Centers for Disease Control and Prevention (CDC): https://www.cdc.gov/radon/index.html
Cleveland Clinic: https://my.clevelandclinic.org/health/diseases/21523-radon-gas
World Health Organization (WHO): https://www.who.int/news-room/fact-sheets/detail/radon-and-health
Oregon Health Authority (OHA): https://www.oregon.gov/oha/ph/healthyenvironments/healthyneighborhoods/radongas/pages/index.aspx
American Lung Association: https://www.lung.org/clean-air/indoor-air/indoor-air-pollutants/radon