Radon Test Came Back High? Your Step-by-Step Action Plan
Your Radon Test Came Back High — Now What?
Discovering that your home's radon level is above 4 picocuries per liter (pCi/L) can feel alarming, but it's important to know two things: you're not alone, and this is a problem with a clear, proven solution. The U.S. Environmental Protection Agency (EPA) estimates that roughly 1 in 15 homes in the United States has elevated radon levels, and millions of homeowners have successfully reduced their exposure through straightforward mitigation.
This guide walks you through exactly what to do next — from confirming your results to hiring the right professionals — so you can get your home's air back to safe levels with confidence.
Understanding What a 4 pCi/L Reading Actually Means
Radon is a naturally occurring radioactive gas that seeps up from soil and rock beneath your home. It's colorless, odorless, and tasteless, which is why testing is the only way to detect it. Long-term exposure is the second-leading cause of lung cancer in the United States, responsible for an estimated 21,000 deaths each year according to the EPA.
The EPA's guidance is broken into clear thresholds:
- Below 2 pCi/L: Considered low risk, though no level of radon is technically "safe."
- Between 2 and 4 pCi/L: The EPA recommends you consider taking action to reduce levels.
- At or above 4 pCi/L: This is the EPA's official action level. Mitigation is strongly recommended.
It's worth understanding the scale here. A reading of 4 pCi/L is roughly equivalent to the radiation exposure of about 200 chest X-rays per year. At 10 pCi/L, you're approaching the radiation dose of a pack-a-day smoker. The good news? Once mitigation is in place, most homes drop below 2 pCi/L — often well below.
Step 1: Confirm the Result With a Second Test
Before you spend money on mitigation, make sure your initial result is accurate. Radon levels can fluctuate based on weather, season, ventilation, and how the test was conducted. A single short-term test is a great screening tool, but it's not the final word.
Short-Term vs. Long-Term Follow-Up Testing
The EPA recommends one of two paths after an elevated short-term test:
- If your first result was between 4 and 8 pCi/L: Conduct a long-term test (90 days to one year) for a more accurate picture of your year-round average exposure.
- If your first result was 8 pCi/L or higher: Conduct a second short-term test right away. If the average of both tests is at or above 4 pCi/L, move forward with mitigation.
For real estate transactions, time is often a factor. In those cases, two simultaneous short-term tests or a continuous radon monitor (CRM) deployed by a certified professional is the gold standard.
Why Use a Certified Tester for Confirmation
DIY test kits are inexpensive and useful, but they can be affected by improper placement, humidity, or shipping delays. For the confirmation test — especially the one that will justify spending several thousand dollars on mitigation — hiring an NRPP (National Radon Proficiency Program) or NRSB (National Radon Safety Board) certified professional is the smarter move. They use calibrated continuous monitors that record hourly fluctuations and provide tamper-resistant, court-defensible results.
Step 2: Understand What's Causing the Radon
Radon enters your home through any opening that connects the interior to the soil. Common entry points include:
- Cracks in the foundation slab or basement walls
- Gaps around plumbing and utility penetrations
- Sump pump pits and floor drains
- Crawl spaces with exposed dirt floors
- Construction joints where the wall meets the floor
- Porous concrete block walls
Homes with basements, slab-on-grade construction, and crawl spaces can all have radon problems. The age, size, and even style of your home doesn't reliably predict radon levels — two identical houses next door to each other can have completely different readings depending on subtle differences in soil composition and foundation sealing.
This is why you can't predict radon levels based on your neighbor's results or your home's age. Testing is the only way to know.
Step 3: Hire a Certified Radon Mitigation Professional
Once you've confirmed elevated levels, the next step is hiring a qualified mitigator. This is not a DIY job for most homeowners — improper installation can actually worsen radon levels, damage your HVAC system, or create dangerous backdrafting of combustion appliances.
What to Look For in a Mitigator
When evaluating contractors, prioritize:
- NRPP or NRSB certification for radon mitigation specifically (not just testing)
- State licensing where required (states like Illinois, Pennsylvania, New Jersey, Florida, and others have specific licensing programs)
- Proof of insurance including general liability
- A written guarantee that the system will reduce radon to below 4 pCi/L (most reputable mitigators guarantee below 2 pCi/L)
- A post-mitigation test included in the price
- Detailed written proposals specifying system components, fan model, warranty, and routing
Get at least 2-3 quotes. Pricing for a typical single-family home ranges from $1,200 to $3,500, with most installations falling in the $1,500-$2,500 range. Unusually complex homes, multiple foundation types, or remote locations can push costs higher.
Red Flags to Avoid
Be cautious of any contractor who:
- Won't show you their certification credentials
- Offers a price dramatically below market rate
- Doesn't include a post-mitigation test
- Promises results without inspecting your home
- Pressures you to decide immediately
Step 4: Understand How Radon Mitigation Systems Work
The most common and effective mitigation method is called Active Soil Depressurization (ASD), also known as Sub-Slab Depressurization (SSD). Here's how it works in plain terms:
A PVC pipe is installed through your basement floor (or through the foundation in slab homes), with one end reaching into the gravel or soil beneath the slab. A specialized in-line fan — typically mounted in the attic or on the exterior of the house — creates continuous negative pressure under the slab. This pulls radon-laden soil gas out before it can enter your living space and vents it safely above your roofline.
Variations Based on Foundation Type
- Basement or slab-on-grade: Sub-slab depressurization (most common)
- Crawl space: Sub-membrane depressurization, which involves sealing the dirt floor with a heavy polyethylene barrier connected to the suction system
- Mixed foundations: Combination systems with multiple suction points
- Block wall homes: Block wall depressurization, which addresses radon trapped inside hollow concrete blocks
A properly designed system runs 24/7, year-round, and uses about as much electricity as a 75-watt light bulb (roughly $75-$150 per year in energy costs). The fan itself typically lasts 5-10 years before needing replacement, which is a relatively inexpensive repair.
What a Good System Includes
A code-compliant mitigation system will have:
- A system label identifying the installer, date, and warning information
- A U-tube manometer (a small clear gauge filled with liquid) that lets you visually confirm the fan is creating suction
- Sealed joints at all visible foundation cracks
- A vent stack that terminates at least 12 inches above the roofline and 10 feet from any window or air intake
- Electrical work performed to local code, typically on a dedicated circuit
Step 5: Verify the System Is Working
Don't assume the job is done when the contractor leaves. The EPA requires a post-mitigation test be conducted no sooner than 24 hours and no later than 30 days after the system is activated. This confirms the system actually reduced radon levels below 4 pCi/L (and ideally below 2 pCi/L).
Reputable mitigators include this test in their quote. If yours doesn't, hire an independent NRPP or NRSB certified tester to verify — this third-party verification adds an extra layer of accountability.
Long-Term Monitoring
Even after mitigation, radon levels can change over time due to:
- Foundation settling or new cracks
- Fan failure or weakening
- Major home renovations
- Changes to HVAC systems
The EPA recommends retesting every two years, or anytime you make significant changes to your home's structure or ventilation. A digital continuous radon monitor (around $150-$250) is a worthwhile one-time investment that lets you check levels anytime in real-time.
Step 6: Address Radon Disclosure if You're Selling
If you're a homeowner planning to sell, you have important considerations. Most states require sellers to disclose known radon test results — even if you mitigated the problem. The good news is that a properly installed mitigation system is generally seen as a positive by buyers, not a negative. It demonstrates that the seller addressed a known issue rather than hiding it.
Keep all documentation: original test results, mitigation system invoice and warranty, post-mitigation test results, and any subsequent retests. This paperwork can speed up your sale and prevent renegotiations.
If you're a buyer who received an elevated radon result during a home inspection, you typically have a few options to negotiate:
- Request the seller pay for mitigation before closing
- Negotiate a credit at closing to cover mitigation costs
- Walk away if the seller refuses to address it
Mitigation should be treated like any other major home repair — fixable, predictable in cost, and not necessarily a deal-breaker.
Common Questions Homeowners Ask
"Can I just open windows to reduce radon?"
Temporarily, yes — ventilation will lower indoor radon. But this isn't a long-term solution. It's energy-inefficient, impractical year-round (especially in extreme climates), and ineffective once windows close. Active mitigation is the only reliable fix.
"Will mitigation affect my home's energy efficiency?"
Modern systems are designed with energy efficiency in mind. The fan uses minimal electricity, and the system shouldn't significantly affect heating or cooling costs. A poorly designed system, however, can pull conditioned air from your home — another reason to hire a certified professional.
"What if I have a passive radon system already?"
Many newer homes (built with radon-resistant construction) have a passive vent stack pre-installed. If your test came back high despite having one, the fix is often as simple as adding an active fan to the existing pipe — typically a less expensive installation.
"Is radon covered by homeowners insurance?"
No, radon mitigation is generally not covered by insurance. However, mitigation costs may be tax-deductible as a medical expense if recommended by a doctor, and some state and local programs offer rebates or low-interest loans for radon work. Check with your state radon office.
"How long does installation take?"
Most single-family home installations are completed in 4-8 hours. You can usually remain in the home during installation, though the contractor will need access to the basement, attic, and exterior.
Don't Wait — Take Action Now
Elevated radon is a health hazard you can't see, smell, or taste — but unlike many environmental threats, it's also one of the most fixable. A properly installed mitigation system typically reduces radon levels by 50-99%, often bringing readings from dangerous double-digit pCi/L values down to under 1 pCi/L.
Every day you wait is another day of unnecessary exposure for you and your family. The good news is that taking action is straightforward: confirm your test, hire a certified professional, install the system, verify the results, and monitor over time.
Find a Certified Radon Tester Near You
Whether you need a confirmation test, a real estate transaction test, or a post-mitigation verification, the most important step is working with someone qualified. NRPP and NRSB certified testers follow strict protocols that ensure your results are accurate, defensible, and trustworthy.
Ready to take the next step? Visit FindRadonTesters.com to search our directory of certified radon testing professionals in your area. Compare local experts, read reviews, and connect directly with certified testers who can help you protect your home and your family's health — starting today.