What Causes High Radon Levels in Your Home

Finding out your home has high radon levels can feel alarming. You may have just gotten a test result back, or a home inspector flagged it during a sale — and now you’re not sure what to do next. Take a breath. High radon is one of the most common and treatable home air quality issues in the United States, and understanding what causes it is the first step toward fixing it. This page will walk you through exactly what’s happening in your home, what the numbers mean, and how qualified independent service providers can help you get things under control.

First Steps Right Now

If you’ve just received a radon test result showing elevated levels, here’s what to do immediately — without panicking.

• Don’t ignore the result. Radon doesn’t go away on its own, and prolonged exposure is the second leading cause of lung cancer in the U.S. after smoking. Acting sooner rather than later genuinely matters.
• Confirm the reading. If your test result is at or above 4 picocuries per liter (pCi/L) — which is the EPA action level — consider running a second short-term test or hiring a certified professional to conduct a more accurate long-term test. Single test results can vary depending on conditions.
• Increase ventilation temporarily. Opening windows and improving airflow in lower levels of your home won’t solve the problem, but it can reduce short-term concentration while you arrange professional help.
• Keep children and pregnant family members away from basements and lower floors where radon concentrations are typically highest, until you’ve had a chance to assess and mitigate.
• Start looking for a qualified provider. Remediation Hero connects homeowners with independent contractors in your area who specialize in radon testing and mitigation.

Understanding the Problem: What Causes High Radon Levels

Radon is a naturally occurring radioactive gas that forms when uranium in soil and rock breaks down. It’s colorless, odorless, and completely invisible — you can’t detect it without a test. The gas seeps up from the ground and can enter your home through a variety of pathways. Understanding what causes high radon levels helps explain why some homes have a serious problem while a neighbor’s house may test fine.

The Soil and Geology Beneath Your Home

The biggest factor in radon levels is what’s in the ground under your home. Homes built on granite, shale, phosphate-rich soils, or uranium-bearing rock tend to have higher radon risk. Some regions of the country — including parts of the Midwest, Mid-Atlantic, and Rocky Mountain states — sit on geology that naturally produces more radon. If you’re in Colorado, for example, radon exposure is a well-documented concern. The same is true in Pennsylvania and Ohio, where elevated radon levels are frequently found in residential testing.

That said, geography alone doesn’t determine your risk. Two homes on the same street can have very different readings. The structure of the house matters just as much.

How Radon Enters Your Home

Radon rises from the ground as a gas and enters homes through gaps, cracks, and openings in the foundation. Common entry points include:

• Cracks in poured concrete foundations or concrete block walls
• Construction joints where walls meet floors
• Gaps around service pipes, sump pumps, and utility penetrations
• Crawl space floors that aren’t properly sealed
• Loose-fitting floor drains in basements
• Cavities inside walls, especially in older construction

The reason radon moves from the soil into the home is pressure. The air pressure inside your home is typically slightly lower than the pressure in the soil around your foundation. This creates a gentle vacuum effect that draws soil gases — including radon — upward and inward. This is why basements and lower floors almost always have higher radon levels than upper floors.

Why Some Homes Trap More Radon

Modern energy-efficient homes — tightly sealed with good insulation — are often more susceptible to high indoor radon levels, not less. The same features that keep your heating and cooling bills down also reduce natural air exchange, meaning radon that enters the home has fewer opportunities to dilute and escape. In an older drafty house, radon might naturally vent before accumulating. In a well-sealed home, it builds up.

Seasonal changes also play a role. Radon levels tend to be higher in winter when windows are closed and heating systems run continuously, further reducing air exchange. This means a test taken in summer may read lower than one taken in January, which is one reason long-term testing over 90 days or more gives a more accurate picture of your actual exposure.

Water as a Radon Source

In homes with well water, radon can also enter through the water supply. Radon dissolved in groundwater can be released into the air when you shower, run the dishwasher, or use the faucet. This is less common than soil-based entry and typically contributes a smaller portion of indoor radon, but it’s worth noting — especially in homes in states like Alaska or rural areas with private wells where groundwater radon testing isn’t always routine.

How Radon Compares to Other Household Issues

Homeowners sometimes wonder whether radon or mold should be their bigger concern. The honest answer is that they’re both serious but different problems. If you’re trying to sort out which issue deserves your attention first, this comparison of radon vs. mold can help you think through the differences and priorities.

When to Act Immediately

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Most radon situations allow for measured, planned action rather than emergency response. However, there are some circumstances where you should move quickly:

• Your test result is 8 pCi/L or higher. At twice the EPA action level, the urgency increases. The EPA recommends fixing your home within a few months at this level, but the sooner you act the better.
• You have young children in the home. Children’s developing lungs may be more vulnerable to radiation exposure over time.
• A family member is already being treated for respiratory illness. Continued radon exposure during treatment is a compounding risk.
• Your home is about to be sold or purchased. Many real estate transactions in 2026 require radon testing as part of the inspection process, and elevated levels can delay closing or affect negotiations. Getting a mitigation system in place beforehand saves time and stress.
• You’ve never tested and have lived in the home for years. Long-term exposure at moderate levels — between 2 and 4 pCi/L — still carries meaningful cumulative risk.

What Professional Help Involves

When you connect with an independent radon contractor through Remediation Hero, here’s a general picture of what the process looks like. Keep in mind every home is different and qualified providers will assess your specific situation before recommending a course of action.

Professional Testing

A certified radon inspector can place professional-grade long-term or short-term detectors in your home and analyze them through an accredited lab. This removes the guesswork from do-it-yourself kits and gives you a more reliable baseline reading. Cities like Minneapolis, Denver, Pittsburgh, and Cleveland have established networks of certified professionals who handle this routinely.

Sub-Slab Depressurization

The most common and effective mitigation technique is called sub-slab depressurization, sometimes called active soil depressurization. A contractor drills one or more suction holes through the foundation slab, inserts a pipe, and connects it to a small fan. The fan creates negative pressure beneath the slab, drawing radon up and out of the soil before it can enter the living space. The pipe is typically routed up through the home and vented above the roofline. This system runs continuously and can reduce radon levels by up to 99% in many homes.

Crawl Space Encapsulation

Homes with dirt crawl spaces require a different approach. A contractor installs a thick polyethylene membrane across the crawl space floor, seals it to the foundation walls, and adds a ventilation system to depressurize the space. This prevents radon and moisture from migrating upward into the living area.

Post-Mitigation Testing

A reputable contractor in your area will always recommend retesting after mitigation is complete — typically 24 to 48 hours after the system is installed. This confirms that levels have dropped to an acceptable range and the system is working as intended.

How to Find Help

Remediation Hero is a homeowner platform that connects you with independent, qualified radon service providers in your area. We don’t perform mitigation services ourselves — instead, we make it easy to find and compare experienced local contractors who are certified and familiar with the specific soil conditions, building types, and climate factors in your region.

Whether you’re in a high-risk zone like the mountain west, or in states with emerging awareness of radon risk like Alabama or Arizona, there are qualified professionals available to help. Getting connected is the first step toward a safer home.

Frequently Asked Questions

What is considered a dangerous radon level in a home?

The EPA recommends taking action when radon levels reach 4 pCi/L (picocuries per liter) or higher. However, the EPA also suggests considering mitigation at levels between 2 and 4 pCi/L, since no level of radon is completely without risk. The average indoor radon level in U.S. homes is about 1.3 pCi/L, and outdoor air typically measures around 0.4 pCi/L. If your reading is above 4 pCi/L, connecting with a certified contractor is the right next step.

Can high radon levels go away on their own?

No. Radon is continuously generated by radioactive decay in the soil and rock beneath your home. It doesn’t diminish over time without intervention. While seasonal fluctuations mean your levels may be slightly lower in warmer months with open windows, the underlying source doesn’t change. Only a properly installed mitigation system — or in some cases, significant sealing of entry points — will reliably and permanently lower your indoor levels.

Does a newer home have lower radon risk?

Not necessarily. In fact, newer homes are often built to be more airtight, which can trap radon more effectively than older, draftier construction. Some newer homes are built with radon-resistant construction features — like a gravel layer beneath the slab, a plastic sheeting barrier, and a rough-in pipe for future mitigation — but these features don’t eliminate risk on their own. Any home, regardless of age, can have elevated radon depending on the local geology and how the building is constructed.

How long does radon mitigation take and how disruptive is it?

In most cases, a standard sub-slab depressurization system can be installed in a single day — typically four to eight hours depending on the home’s size and foundation type. The work involves drilling through the slab, routing a small pipe, and installing a fan unit. Most homeowners find the process minimally disruptive. You can remain in the home during installation in most situations, and the system operates silently in the background once running. Independent contractors in your area can give you a more specific timeline after assessing your home.

Is radon testing required when buying or selling a home?

Requirements vary by state and municipality, but radon testing has become increasingly standard as part of the home buying process. Even where it isn’t legally required, many buyers now request radon testing as part of the home inspection. If elevated levels are found, mitigation can often be negotiated as part of the sale terms. If you’re selling a home in a known radon zone, having a mitigation system already in place can actually be a positive selling point and remove a potential obstacle from your transaction.

Remediation Hero connects homeowners with independent service providers. We do not perform remediation, mitigation, abatement, inspection, or cleanup services directly. Independent providers set their own pricing, availability, and service terms. Results, response times, and provider availability are not guaranteed.