If Your Test Is High
If Your Test Comes Back High: Fixing Radon, Explained.
The short version: if your 48-hour test came back at or above 4.0 pCi/L — the level where the EPA says to fix your home — the next step is a fix. That's not a cleanup or a haul-off — radon is a gas, and the fix is a vent system that pulls soil gas out from under the house and sends it above the roof. Here is what that actually involves, and how to pick the person who installs it.
4.0pCi/L
EPA action level for fixing
0.4pCi/L
US average outdoor radon
48hrs
post-mitigation verification test
Vented, Not Disposed
What “Fixing” Radon Actually Means
Radon is a gas. It seeps up from the soil and rock underneath your house through cracks, gaps around plumbing penetrations, sump pits, floor-to-wall joints, and any other opening between the soil and the interior air. It is not a spill you clean up. It is not sludge you haul off. There is nothing to remove.
A radon mitigation system does not destroy radon. It redirects it. It pulls the soil gas that would have entered your house out from under the slab (or out of the crawlspace) and pipes it up above the roofline, where it disperses into outdoor air. Outdoor radon averages about 0.4 pCi/L in the US — the fix works because the atmosphere is a very large dilution.
How the System Works
Sub-Slab Depressurization, in Plain English
The standard fix for most homes is called active sub-slab depressurization — in plain English, a pipe and a quiet fan that pull the gas out from under your floor and vent it above the roof. Here are those three parts up close.
- A suction point through the slab. The installer drills a hole through the concrete floor of the basement or slab-on-grade, cleans out a small pocket of the material underneath, and seats a PVC pipe there.
- A run of PVC pipe to the outside. The pipe leaves the suction point, routes through the interior or exterior of the house, and continues up until it discharges above the roofline — higher than any window or intake.
- An inline fan. A quiet, continuously running fan on the pipe creates a slight vacuum under the slab. That vacuum is what pulls soil gas into the pipe instead of letting it seep up through the floor.
The system works on both slab-on-grade and basement homes. A crawlspace usually gets a sealed vapor barrier over the exposed soil first, and the suction point pulls from underneath that membrane. The physics is the same — create a small pressure difference so radon takes the pipe instead of the living space.
A U-tube pressure gauge (a “manometer”) mounted on the pipe shows at a glance whether the fan is actually pulling. As long as the two liquid levels in the U-tube are offset, the system is working; if they equalize, the fan is off or the pipe is blocked and it needs service.
Cost
What It Costs (and Why We Do Not Quote It)
The EPA's guidance is that radon mitigation costs vary with the home's design, foundation type, and how difficult the pipe routing is. A slab-on-grade ranch with an obvious exit path is not the same job as a two-story house on a basement with a finished ceiling and no simple exterior route.
We do not publish a mitigation price on this page, and we are not going to invent one. We do not sell mitigation. What you should know is:
- Mitigation quotes are free. A reputable mitigator will walk the house and give you a written quote at no cost.
- Get more than one. Two or three quotes on the same job is normal. The right number will come from the routing complexity and the credential of the installer, not from bundling with anything else.
- Do not pay for testing bundled with mitigation. A mitigator who grades their own before/after tests is the exact conflict of interest this whole industry is supposed to avoid.
Source: US EPA, “A Citizen's Guide to Radon,” on mitigation cost and the strong recommendation to hire a qualified contractor.
Choosing a Mitigator
How to Pick a Mitigation Contractor
Alabama does not license radon professionals at the state level. The credential to ask about is the national one:
- NRPP mitigation certification — the National Radon Proficiency Program certifies mitigation providers separately from testing. Ask for the certification number and confirm it is current.
- AARST membership — the American Association of Radon Scientists and Technologists is the standard-setting body behind the ANSI/AARST protocols. Members follow those standards.
- Written scope — the quote should identify the suction point, the fan model, the routing, the discharge height above roofline, and who handles the electrical connection.
- Post-mitigation verification — ask specifically how the system's performance will be verified after installation. The honest answer is a fresh 48-hour test, and the strongest version of that answer is a test placed by someone other than the mitigator.
Two or three qualified NRPP-certified quotes, with the same scope of work on each, is the way this decision gets made. There is no reason to rush it.
Our Pledge
The No-Kickback Pledge
We don’t take a dime from any mitigation company — no referral fees, no partnerships, no cut. That’s the whole point of independent testing.
We test. We hand you the lab report. You choose your mitigator freely.
Mitigation contractors are independent of us, and they should be. You will not read us calling them “our team” on this website, because they are not. If we took a piece of the mitigation invoice, then every test we placed would carry a quiet incentive to come back high — and the number on the lab report would stop being trustworthy the moment we signed that agreement.
Our job ends with a lab-scored report from an independent lab. That report is yours. You take it to whichever NRPP-certified mitigator you choose, or to a second opinion, or to a seller in a negotiation. We do not follow it out the door and we do not clip a fee off the fix.
Verify the Fix
After the System Is Installed: The Verification Test
A mitigation system is not finished the day the fan turns on. The finish line is a fresh 48-hour closed-building test that confirms the home's average radon level dropped below 4.0 pCi/L. That test is the answer to the only question that actually matters: did the fix work?
The strongest version of that verification is placed by someone who did not sell you the system. That is the exact independence gap we exist to fill. It is the same 48-hour ANSI/AARST protocol, the same sealed continuous monitor, the same independent lab read — run against the newly mitigated house instead of against a house being bought and sold.
After that, retest on roughly a two-year cycle. Fans wear out, seals settle, and small foundation cracks open up over time. See how radon testing works for the full protocol, and what a safe radon level actually is for the reading standards. If your original test came back in the 2–4 pCi/L band and you are trying to decide whether a fix is even warranted, see radon levels between 2 and 4 pCi/L.
Just had a mitigation system installed? Verify it with an independent 48-hour test.
FAQ
Frequently Asked Questions
What actually happens to the radon — is it destroyed?
No. Radon is not destroyed and it is not trapped. It is vented. A sub-slab depressurization system pulls soil gas from under the slab or crawlspace and pipes it up above the roofline, where it disperses into outdoor air. Outdoor radon is very low (about 0.4 pCi/L on average in the US), so venting is the accepted fix.
How much does radon mitigation cost?
National guidance from the EPA is that mitigation costs vary with home design, foundation type, and how difficult the routing is. Mitigation contractors quote for free and price the job to your specific house. We do not quote mitigation, we do not upsell it, and we do not take a referral fee for sending you to anyone.
Do I need someone certified to install the system?
Alabama does not license radon professionals at the state level. The credential to look for is NRPP (National Radon Proficiency Program) or AARST certification specifically for mitigation. It is a different credential than testing certification. Get 2 or more quotes, ask about the credential, and ask how they will verify the system worked once it is installed.
How do I know the mitigation actually worked?
With a post-mitigation test. The point of a post-mitigation test is to confirm that the new system brought the home's average radon level below 4.0 pCi/L over a 48-hour closed-building test. The strongest version of this is an independent test — a test placed by someone who does not sell or install mitigation. That is what we do.
Do you take a referral fee from mitigation companies?
No. Not a dime. No referral fees, no partnerships, no cut of the mitigation invoice, no revenue share, no lead sale. Independence from the mitigation industry is the whole point of independent testing, and if we took a cut of the fix, the number we hand you would no longer be trustworthy.
A post-mitigation verification test is $295, same 48-hour protocol as any other test we place. Related reading: how radon testing works · what a safe radon level is · radon 2–4 pCi/L.