What Is Radon: The Invisible Guest

When homeowners list their biggest structural worries, they usually point to what they can see: a sagging roof, a cracked foundation, or outdated electrical wiring. Yet one of the most serious hazards inside your home is completely invisible. It has no smell, no color, and no taste.

It’s called radon—a naturally occurring radioactive gas that seeps into houses from the surrounding soil. Long-term exposure to radon is the second leading cause of lung cancer in the United States. Learning how radon behaves, how it enters your living spaces, and how to eliminate it is one of the most vital steps you can take to protect your household.

Key Takeaways

• Unseen and Unnoticed: Radon is a colorless, odorless, tasteless radioactive gas formed by the decay of uranium underground. You cannot detect it without testing.
• A Major Health Risk: Responsible for roughly 21,000 U.S. lung cancer deaths every year, radon affects smokers and non-smokers alike.
• Testing Is Simple: Easy-to-use short-term and long-term test kits provide a clear answer about your home’s indoor air quality.
• Proven Solutions: Active sub-slab depressurization systems routinely cut indoor radon levels by 45–90% or more.
• Local Expertise: Dor-Mar Heating, Air Conditioning & Plumbing provides radon assessment, mitigation, and indoor air safety solutions across Central Ohio and Southwest Florida.

What Is Radon? (Simple Explanation First)

Radon is a naturally occurring radioactive element in gas form that forms underground when uranium in soil and rock breaks down through a process called radioactive decay. It is produced by the decay of uranium in soil and eventually becomes radon gas after passing through several intermediate elements, including radium-226.

Because radon is an odorless gas that is also colorless and tasteless, people cannot detect it with their senses. There is no way to know radon is present in your home without a test. Think of it like water seeping through tiny cracks in a basement wall, except radon is an invisible gas that rises from the soil and enters through foundation gaps, pipe openings, and sump pits.

Outdoors, radon disperses quickly and remains at very low concentrations. But when it seeps into an enclosed space like a home, it can build up to levels that pose a real danger to your health. This process of accumulation is what turns radon from a harmless trace gas in the atmosphere into a potential indoor hazard.

Radon as a Naturally Occurring Radioactive Gas

Radon-222, the most common gaseous form of this element, is a naturally occurring radioactive gas that belongs to the noble gas family on the periodic table. It is chemically inert and not very reactive under normal conditions, though it can be oxidized by fluorine to form radon difluoride (RnF2) in laboratory settings. Its real-world danger has nothing to do with chemical reactions and everything to do with radiation.

The half-life of radon-222 is 3.82 days. That means half of any given quantity of radon decays within about four days. Radon has a density of 9.73 kg/m³ at standard conditions, making it heavier than air. When radon decays, it doesn’t simply vanish. Instead, as part of a radioactive decay chain, it transforms into a series of short-lived solid particles called radon progeny, or “radon daughters.” These progeny attach to dust particles and aerosols floating in indoor air.

Here’s where the health risk begins. When you breathe in air containing these particles, they can lodge deep in your lung tissue. As the radon progeny continue to decay, they emit alpha particles, a form of ionizing radiation. Alpha particles are heavy and highly energetic. While they can’t penetrate your skin, inside the delicate tissue of your lungs, they can damage cellular DNA. Over years of exposure, this cumulative DNA damage raises the risk of developing lung cancer.

How Radon Gets Into Your Home

Radon can enter homes through cracks in foundations and walls, and it does so more easily than most people realize. Here are the most common entry points:

• Cracks in concrete slabs and foundation walls
• Construction joints where walls meet the floor
• Gaps around service pipes, wiring, and utility penetrations
• Sump pump pits and floor drains
• Hollow block walls and porous concrete
• Crawl space floors with exposed soil

Radon can enter buildings through cracks in floors and gaps around pipes due to pressure differences between the soil and the interior of your home. This is driven by what professionals call the “stack effect.” Warm air inside your home naturally rises and escapes through upper-story windows, attic vents, and other openings. To replace that escaping air, the house pulls in air from the lowest available source, which is often the soil beneath and around the foundation. That soil air frequently contains radon.

Any type of home can have elevated indoor radon. Old houses, new construction, homes with basements, slab-on-grade buildings, and even well-sealed structures can all accumulate radon indoors. Local geology, including the uranium content of the underlying soil and rock, plays a major role in how much radon is available. But so do home design, foundation type, and ventilation patterns.

Radon can also be released indoors from groundwater when using well water during activities such as showering, which is a less common but real pathway.

Where Radon Levels Tend To Be Highest

Radon concentrations are typically highest in the lowest levels of a home. Basements, ground-floor rooms, and crawl-space-level areas tend to accumulate the most radon because they are closest to the soil source. Radon typically accumulates in poorly ventilated areas like basements and ground floors, where air exchange with the outdoors is minimal.

Radon exposure is highest in poorly ventilated buildings overall. Enclosed rooms near sump pits, utility areas, and foundation walls are common hot spots. If you’ve finished your basement into a living space but haven’t tested, that room could be exposing your family to elevated levels without anyone knowing.

The average outdoor radon level in the U.S. is about 0.4 pCi/L, roughly 15 Bq/m³. Outdoor radon concentrations are generally diluted to low levels compared to indoor levels. Inside homes, the national average is around 1.3 pCi/L, but radon levels vary widely. Some homes measure well above 10 pCi/L, and in extreme cases, radon levels can reach 100,000 Bq/m³ in homes.

One critical point: homes in the same neighborhood, even next door to each other, can have drastically different radon levels. Soil composition, foundation construction, and ventilation patterns can all change from one property to the next. Map-based radon zone classifications are useful for general awareness, but they cannot predict radon in a specific house. Only testing can.

Homeowners in Central Ohio and Southwest Florida should test regardless of their zip code or county risk classification.

Health Effects of Radon: Why It Matters

The primary health effect of exposure to radon is lung cancer. There are no short-term symptoms. Radon does not cause headaches, nausea, dizziness, or allergic reactions. People exposed to radon typically feel completely normal for years or even decades before any health effects appear.

Radon gas can damage lung cells and lead to cancer over time. The mechanism is straightforward: inhaled radon decay products emit ionizing radiation inside the lungs, gradually damaging the DNA in lung tissue. Over many years, this damage can trigger the uncontrolled cell growth that becomes lung tumors.

According to major health organizations, radon is the leading cause of lung cancer among non-smokers and the second leading cause of lung cancer overall. Radon exposure raises the risk of lung cancer in both non-smokers and smokers, with the danger much higher for smokers, which is why this risk applies to every household.

Because you cannot smell radon or feel its effects, long-term health risks are easy to overlook. Radon is not a rare problem. It is a common indoor air health hazard that can be measured with simple testing and controlled with proven mitigation systems. The key is awareness and action.

Radon, Lung Cancer, and Lung Cancer Deaths

The numbers paint a sobering picture. Approximately 21,000 lung cancer deaths per year in the U.S. are linked to radon, according to estimates from the U.S. Environmental Protection Agency. That makes radon the leading cause of lung cancer after cigarette smoke.

Radon is recognized as a proven human carcinogen by the EPA, the World Health Organization, and the American Cancer Society. These are not speculative claims. They are backed by decades of epidemiologic evidence from studies of both residential populations and occupational groups.

Radon-related lung cancer often develops after many years of continuous exposure. Because lung cancer symptoms, such as persistent cough, chest pain, and shortness of breath, can mimic other respiratory conditions, radon-related cases are frequently diagnosed at advanced stages. Deaths occur that might have been prevented with earlier testing and mitigation.

There is no established “safe” level of radon. Risk decreases as radon concentrations go down, but even low to moderate levels carry some increased risk over a lifetime of exposure. For this reason, the EPA recommends testing homes below the third floor and taking action when levels are elevated.

If you or anyone in your household has a personal or family history of lung disease, radon testing should be a priority.

Radon Risk If You Smoke or Have Smoked

Radon exposure increases lung cancer risk for smokers significantly. The relationship between radon and cigarette smoke is not simply additive; it is multiplicative. That means the combined effect of smoking and radon exposure is far greater than either risk factor alone.

Here’s a practical comparison based on EPA risk estimates:

A smoker living in a home at 4 pCi/L faces roughly five to six times the lung cancer risk of a never-smoker at the same radon level. Even former smokers carry a higher risk than people who have never smoked.

If you smoke or have smoked, two actions can dramatically cut your risk of developing lung cancer: test and mitigate radon in your home, and pursue smoking cessation. Healthcare providers and organizations like the American Cancer Society can offer support for quitting. Combining both steps is one of the most effective ways to reduce your overall radon risk.

Scientific Evidence Linking Radon to Lung Cancer

The connection between radon and lung cancer was first identified in studies of uranium miners who were exposed to radon at extremely high concentrations over long periods. These occupational studies provided the earliest clear epidemiologic evidence that radon leads to lung cancer.

In the early 2000s, large pooled studies from North America and Europe examined residential radon exposure specifically. These studies confirmed that the cancer risk observed in miners also applied at the lower radon concentrations commonly found in homes. The evidence was consistent: long-term residential radon exposure increases lung cancer incidence in a dose-dependent manner.

The National Research Council’s BEIR VI report, published by the National Academy Press, was a landmark scientific review. It concluded that indoor radon is a significant public health problem and estimated thousands of lung cancer deaths annually in the U.S. attributable to home radon exposure. The National Academy of Sciences’ analysis remains foundational.

Researchers have also examined potential non-pulmonary neoplasm risk from radon, though the evidence for cancers outside the lung is far less established. Some studies published in journals covering environ res public health have explored these questions, but the scientific consensus remains firmly focused on lung cancer as the primary outcome.

These findings have led government agencies worldwide to promote widespread radon testing and mitigation as a public health priority.

What Do Major Health Organizations Say About Radon?

The consensus among health and scientific authorities is clear. Here is what the major organizations state:

• The US Environmental Protection Agency identifies indoor radon as a leading environmental cause of cancer mortality in the U.S. The EPA recommends testing all homes and fixing those at or above 4 pCi/L.
• The World Health Organization estimates that radon may be responsible for 3–14% of lung cancer cases worldwide, depending on national radon levels and smoking prevalence.
• The American Cancer Society describes radon as a proven cause of lung cancer, supported by strong scientific evidence from multiple study designs.
• Former leaders of the U.S. Public Health Service, including past Surgeons General, have issued national health advisories urging Americans to test their homes and take steps toward radon reduction when levels are high.
• The Centers for Disease Control and Prevention (CDC), under the Department of Health and Human Services, provides guidance on radon prevention as part of its disease control mission.

The United States government, through multiple agencies, treats radon as a preventable environmental health risk. The EPA recommends testing for every home, and government agencies at the state level often provide free or low-cost test kits to encourage homeowner action.

How Radon Is Measured and What Levels Mean

Radon concentrations in air are measured in picocuries per liter (pCi/L) in the U.S. Internationally, the unit is becquerels per cubic meter (Bq/m³). The conversion is straightforward: 1 pCi/L equals approximately 37 Bq/m³.

Here are the key reference points:

Radon levels can fluctuate daily due to weather conditions, seasonal changes, and ventilation patterns. A single measurement is a snapshot, not a permanent reading. This is why the EPA and radon professionals recommend following specific testing protocols and considering long-term testing for the most accurate picture.

The EPA recommends fixing homes at or above 4 pCi/L and considering mitigation for levels between 2 and 4 pCi/L. If your test results fall in an uncertain range, working with a certified radon professional can help you interpret the numbers and decide on next steps.

Testing Your Home for Radon

Radon testing is the only way to know if your home has elevated radon levels. Since you cannot smell radon, see it, or feel its effects, testing is non-negotiable for responsible homeownership.

There are two main types of tests:

• Short-term radon tests last from 2 to 90 days and are useful for initial screening. These are the most common starting point.
• Long-term tests run from 90 days up to a full year and provide a more accurate annual average, smoothing out the natural fluctuations caused by weather and seasonal changes.

Radon test kits are available at hardware stores, through state radon programs, and online. Many state health departments offer free or discounted kits. You can also hire a certified radon professional to conduct testing with continuous monitoring equipment.

Basic testing steps:

1. Place the kit on the lowest lived-in level of your home (basement or first floor).
2. Position it away from drafts, high humidity areas, exterior walls, and windows.
3. Keep windows and exterior doors closed as directed during the test period.
4. After the test period, seal and mail the kit to the designated lab for analysis.

Testing during colder months is often recommended because homes are more closed up, and indoor radon tends to be at its highest. Radon levels fluctuate naturally due to weather conditions, so follow local or EPA guidance on timing for the most representative results.

What To Do If Your Radon Levels Are High (Radon Mitigation)

Radon levels above 4 pCi/L require mitigation steps. The EPA recommends radon mitigation for levels above 4 pCi/L, and many homeowners also choose to act at lower levels for additional safety.

The most common and effective mitigation method is sub-slab depressurization, also known as an active mitigation system. Here’s how it works:

1. A contractor drills a small hole through the basement slab or crawl space floor.
2. A suction pit is created beneath the slab.
3. PVC piping connects the pit to a continuously running fan.
4. The fan pulls radon-laden soil gas from beneath the foundation and vents it safely above the roofline, away from windows and air intakes.

For homes with a crawl space, sub-membrane depressurization is the standard approach. A heavy plastic sheet is sealed over the crawl space floor, and a fan draws radon from beneath the membrane.

Radon mitigation systems can reduce indoor levels by 45–90%, with many properly designed systems achieving reductions in the 70–95% range. Sealing cracks and construction joints is always part of the process, though sealing alone is usually not enough to solve a radon problem.

A typical radon mitigation system installation costs between $800 and $2,500 for most single-family homes. Operating costs are modest, similar to running a small household appliance.

After installation, post-mitigation verification testing is essential to confirm that radon levels have dropped below the target. Ongoing maintenance includes checking fan operation and sealing integrity periodically.

If you’re in Central Ohio or Southwest Florida, Dor-Mar Heating, Air Conditioning & Plumbing offers professional radon assessment and mitigation services, including free estimates.

Radon in New Homes and During Real Estate Transactions

Many people assume that a brand-new home is safe from radon. That’s not the case. Even new construction can have high indoor radon because radon levels depend primarily on local soil conditions and building design, not the age of the house.

Modern building codes increasingly call for radon resistant features in new construction. These features include:

• A gas-permeable layer (gravel) beneath the foundation slab
• Heavy-duty plastic sheeting over the gravel to block soil gas
• Sealed construction joints and cracks
• A vent pipe running from the sub-slab area to above the roofline
• Proper sealing around penetrations

These features make it easier and less expensive to add an active fan later if testing reveals elevated levels.

In real estate transactions, radon testing has become a routine part of the home inspection process. Many buyers and lenders now expect a radon test before closing. If levels are high, mitigation is sometimes negotiated as part of the purchase agreement, similar to other home repairs.

A quick checklist for buyers and sellers:

• Schedule a radon test early in the inspection period.
• If buying, request results from any previous radon testing.
• If levels are high, get a mitigation estimate before finalizing negotiations.
• After mitigation, retest to confirm levels are acceptable.
• Keep documentation of all testing and mitigation work for future reference.

Radon Exposure at Work and in Certain Jobs

Most people’s largest exposure to radon comes from time spent in their home. However, certain occupations carry a higher risk. Uranium miners historically faced the greatest occupational radon exposure, and uranium miners can be exposed to radon levels over 1,000,000 Bq/m³ in unventilated underground environments. Tunnel workers, some water-treatment facility employees, and workers in certain mining and geological industries may also face elevated levels.

In the U.S., agencies such as OSHA and the Nuclear Regulatory Commission set occupational limits for radon and other ionizing radiation exposures. Employers in higher-risk industries are required to monitor and control radon levels to protect workers’ health.

If you suspect elevated radon exposure on the job, speak with your workplace safety officer or consult official guidance from the Agency for Toxic Substances and Disease Registry. But for most people, the single most important step is testing the home where you spend the majority of your time.

Radon in Central Ohio

Central Ohio has widespread areas of elevated radon potential. The region’s geology, including glacial till, shale bedrock, and varying soil uranium content, creates conditions that produce and transport radon gas efficiently. Many homes across Franklin County and surrounding areas test above the EPA action level, regardless of whether they’re in a designated “high-risk” zone.

Southwest Florida is often perceived as a lower-risk area, but that perception can be misleading. Sand and limestone geology can permit rapid diffusion of radon, and homes with slab foundations or tightly sealed construction can still accumulate significant radon indoors, particularly when ventilation is limited. Radon is a geological hazard that can become a public health hazard indoors in any region.

County-level radon maps show general trends, but they cannot predict radon levels for an individual house. The only reliable way to know your home’s radon status is to test it.

Dor-Mar Heating, Air Conditioning & Plumbing has decades of experience working with local housing styles in both Central Ohio and Southwest Florida. Our technicians understand common radon entry patterns in these regions and can recommend solutions tailored to your home’s specific foundation and construction type.

If you’re in our service areas, consider scheduling radon testing or mitigation as part of a broader indoor air quality evaluation.

How Radon Fits Into Overall Indoor Air Quality

Radon is one of several indoor air quality concerns homeowners should be aware of, alongside issues like excess humidity, carbon monoxide, mold, volatile organic compounds, and particulate matter. But unlike most indoor pollutants, radon is a major source of ionizing radiation exposure and the leading environmental cause of lung cancer. That places it in a category of its own when it comes to long-term health risk.

Your HVAC system, ventilation strategy, and building tightness all affect how radon builds up and disperses indoors. A tightly sealed, energy-efficient home is great for heating and cooling costs but can also trap radon more effectively if no mitigation is in place. Conversely, improving ventilation can help reduce radon concentrations, though it’s rarely sufficient on its own in high-radon homes.

At Dor-Mar, we can pair radon solutions with other indoor air quality services, including air filtration, dehumidification, and ventilation improvements. Radon is one piece of the puzzle. Natural substances in soil, volatile chemicals from building materials, and biological contaminants all contribute to the air you breathe every day.

A comprehensive indoor air quality check, rather than a single one-time radon test, provides the most complete picture of your home’s air environment and the best foundation for long-term health benefits.

Working With Dor-Mar for Radon and Home Comfort Solutions

Dor-Mar Heating, Air Conditioning & Plumbing is a family-operated home comfort provider that has served Central Ohio and Southwest Florida since 1962. In addition to heating, cooling, plumbing, electrical, and appliance repair, we offer radon mitigation and indoor air quality services designed to keep your family safe and comfortable.

Here’s what a typical radon service visit looks like:

1. Initial consultation and assessment of your home’s foundation, ventilation, and risk factors.
2. Radon testing or review of your existing test results.
3. Custom system design based on your home’s construction and soil conditions.
4. Professional installation of the mitigation system, usually completed in a single day.
5. Post-mitigation verification testing to confirm radon levels have been reduced to safe ranges.

We offer free estimates for radon mitigation systems and can bundle radon work with other home comfort services like HVAC upgrades, water treatment, and dehumidification. If you’re interested in ongoing maintenance and safety checks, ask about our Home Comfort Membership.

Whether you need a first-time radon test, a full mitigation system, or a comprehensive indoor air quality evaluation, we’re here to help. Schedule service online, call us for a consultation, or visit our website to learn more about everything we offer.

Frequently Asked Questions About Radon

Can I feel sick from radon right away?

No. Radon does not cause immediate symptoms like dizziness, headaches, or nausea. Most people exposed to radon feel completely normal for years or even decades. The main health effect is an increased long-term risk of developing lung cancer, which may not show symptoms until the disease is advanced. This lack of short-term warning signs is exactly why regular radon testing is so important. You won’t know there’s a problem unless you test.

Is it safe to live in my home while a radon system is being installed?

In most cases, yes. A typical radon mitigation system installation takes about a day, and homeowners can usually remain in the house during the work. Technicians may ask you to avoid certain areas temporarily while equipment is being installed for safety and convenience. Once the system is running and post-mitigation testing confirms lower levels, your home is safer for long-term occupancy than it was before.

How often should I retest my home for radon?

The general recommendation is to retest at least every two to five years. You should also retest sooner if you make major structural changes to your home, install a new HVAC system, finish a basement, or add or repair a mitigation system. Homeowners in areas with known elevated radon or those who previously had borderline results may want to test more frequently for peace of mind. Radon levels can change over time as soil conditions, weather patterns, and home characteristics shift.

If my neighbor’s house has low radon, does that mean mine is safe too?

Not at all. Radon levels can vary dramatically from one home to another, even on the same street or in attached housing. Differences in construction, foundation type, soil conditions directly beneath the house, and ventilation can all cause significant differences in indoor radon concentrations. Every home needs its own radon test. A neighbor’s result tells you nothing reliable about your own radon risk.

Will a radon mitigation system increase my energy bills or be noisy?

A properly installed mitigation fan typically uses about as much electricity as a small household appliance, adding only a modest amount to monthly energy bills, often in the range of a few dollars per month. Systems are usually designed to minimize noise, with fans installed in attics, garages, or on the exterior of the home rather than in living spaces. If noise or energy use is a concern, discuss your preferences with your radon contractor so the system can be tailored to your home and comfort needs. Fan lifespan is typically five to ten years, with replacement costs of a few hundred dollars.

Steven Brewer

I started in the HVAC business as a young man, with my father putting me in crawl spaces to run ductwork while on summer vacation from school; I began full time in our family HVAC business at the age of 19.

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