Protecting yourself from radon starts with testing your home, since this invisible, odorless gas is the leading cause of lung cancer among nonsmokers. The EPA recommends taking action if your home’s radon level reaches 4 pCi/L (picocuries per liter) or higher, but there’s no truly “safe” level. The good news: once you know your levels, effective solutions exist at every price point.
Why Radon Is Worth Taking Seriously
Radon is a radioactive gas that forms naturally as uranium in soil and rock breaks down. It seeps through cracks in foundations, gaps around pipes, and any opening where your home contacts the ground. Once inside, it gets trapped and builds up to concentrations far higher than outdoor air.
When you breathe radon, its decay products lodge in your lung tissue and emit alpha radiation. These particles are heavy enough to directly damage DNA in lung cells, generating reactive molecules that overwhelm the body’s normal repair systems. Over years of exposure, this accumulated damage raises your risk of lung cancer significantly. The EPA estimates radon causes roughly 21,000 lung cancer deaths per year in the United States. Smokers exposed to elevated radon face an especially high combined risk, but nonsmokers are far from immune.
Test Your Home First
You can’t smell, see, or taste radon, so testing is the only way to know your levels. Inexpensive test kits are available at hardware stores and online, typically for under $20. There are two types to know about.
Short-term kits measure radon over 2 to 90 days and give you a quick snapshot. They’re useful as a first screening, but radon levels fluctuate with weather, soil moisture, and how often you open windows. A long-term kit, which stays in place for more than 90 days, gives you a much more accurate picture of your year-round average exposure. The CDC notes that the longer the test runs, the better it reflects your actual living conditions.
Place the test in the lowest lived-in level of your home, ideally a basement or ground-floor room you use regularly. Keep windows and exterior doors closed as much as practical during the test. If a short-term test comes back at or above 4 pCi/L, follow up with a second test to confirm before investing in mitigation. If your initial reading is very high (above 8 pCi/L), a second short-term test is reasonable so you can act quickly.
How Professional Mitigation Works
The most common and effective fix is called active soil depressurization. A contractor drills a hole through your basement slab or crawlspace floor, digs a small pit beneath it, and installs a PVC pipe that runs from that pit up through the house and out the roof. A small, continuously running fan attached to the pipe creates suction beneath the foundation, pulling radon-laden soil gas from under the slab and venting it safely above the roofline before it ever enters your living space.
This system typically reduces indoor radon by 80 to 99 percent. Most homeowners pay between $500 and $1,500 for a professional installation, with a median cost around $750. The fan uses about as much electricity as a single light bulb. Once installed, the system runs quietly in the background and requires very little maintenance beyond occasionally checking that the fan is still operating, which a simple pressure gauge on the pipe can tell you at a glance.
After installation, you should retest your home to confirm levels have dropped below 4 pCi/L. Periodic retesting every two years or after major renovations is a smart habit.
What You Can Do Yourself
Sealing foundation cracks, gaps around plumbing, sump pit covers, and floor-wall joints is a reasonable first step, and it’s something you can do on a weekend with caulk and hydraulic cement. But here’s the reality: sealing alone is almost never enough to bring elevated radon levels down to safe ranges. Radon finds pathways you can’t see and can’t seal, including the concrete slab itself, which is slightly porous.
Sealing works best as a complement to an active depressurization system, not a replacement. It helps the fan maintain stronger suction beneath the slab by reducing the number of openings where indoor air gets pulled down. Think of it as tightening the seal on a vacuum cleaner hose so the suction is more effective where it matters.
Improving ventilation in your basement or crawlspace by opening vents or running exhaust fans can modestly reduce radon in the short term, but it’s inconsistent and energy-costly in cold climates. It’s a temporary measure, not a long-term solution.
Radon Protection for New Construction
If you’re building a new home, incorporating radon-resistant features during construction is far cheaper than retrofitting later. The EPA recommends a set of passive techniques that can be activated with a fan if testing later shows elevated levels.
- Gas-permeable gravel layer: A 4-inch bed of clean, coarse gravel beneath the foundation slab allows soil gases to flow freely instead of building pressure against the concrete. In regions where gravel is expensive, perforated pipe or collection mats serve the same purpose.
- Plastic sheeting: Heavy-duty 6-mil polyethylene laid over the gravel acts as a vapor barrier, blocking soil gas from migrating upward through the slab. It also keeps wet concrete from clogging the gravel layer during the pour.
- Vent pipe: A PVC pipe runs from the gravel layer up through the house and out the roof, giving soil gas a path to escape. Initially it works passively through natural air pressure differences. If post-construction testing shows radon above 4 pCi/L, a fan can be added to the pipe to create active suction, converting the passive system into a full mitigation system for a fraction of the retrofit cost.
Adding these features during construction typically costs a few hundred dollars. Retrofitting an existing home with an equivalent system costs two to five times more, so it’s worth insisting on radon-resistant construction even if your area isn’t considered high-risk.
Radon in Well Water
Radon doesn’t only enter through the ground beneath your house. If your home uses a private well, radon dissolved in groundwater can be released into the air when you shower, wash dishes, or run the tap. Public water systems that draw from surface water (rivers and reservoirs) rarely have significant radon, but well water drawn from bedrock can carry substantial concentrations.
Aeration systems are the most effective treatment for waterborne radon. These devices bubble air through or spray water in a chamber, allowing dissolved radon to escape into the air, which is then vented outside. Depending on the design, aeration can remove 78 to 95 percent of radon from water. Granular activated carbon filters are another option, though their effectiveness varies more widely (roughly 40 to 80 percent removal) and they accumulate radioactive material over time, which requires careful disposal.
If you have a private well, testing your water for radon is a separate step from testing indoor air. Your local health department can point you to certified labs that handle water radon analysis.
High-Risk Areas and Who Should Test
Radon levels vary enormously from one house to the next, even on the same street. Geology matters: homes built over granite, shale, or phosphate-rich soils tend to have higher levels. The EPA publishes a map dividing U.S. counties into three radon zones, but the agency is clear that every home should be tested regardless of zone. Homes in “low-risk” areas regularly test above the action level, and homes in high-risk zones sometimes test low.
Certain home characteristics increase the odds of elevated radon. Basements and slab-on-grade foundations are more vulnerable than raised foundations with open crawlspaces, simply because they have more surface contact with the soil. Tightly sealed, energy-efficient homes can trap radon more effectively than drafty older houses. If you’ve recently weatherized your home, retesting is a good idea even if a previous test came back low.
Real estate transactions often include radon testing, but if yours didn’t, or if it’s been several years, a fresh test is cheap insurance. A $15 test kit and a week of patience can tell you whether you need a system that will protect your household for decades.