A long-term radon test measures your home’s radon level continuously for 91 days to a full year using a small alpha track detector, giving you a true seasonal average instead of a one-week snapshot. It’s the most accurate way to know what you’re actually breathing year-round, and it’s what the EPA recommends as a follow-up whenever a short-term test comes back near or above 4.0 pCi/L.
What is a long-term radon test?
A long-term radon test uses a passive alpha track detector, a small badge-sized device with no batteries or moving parts, placed in the lowest lived-in level of your home for at least 90 days. Unlike a short-term charcoal canister test, it doesn’t require closed-house conditions the whole time. Life goes on: windows open in the spring, the AC cycles normally, doors get used. That’s the point. It’s measuring your real, everyday exposure across changing weather, not a lab-controlled snapshot.
At the end of the placement period, the detector goes to a lab for analysis and the result comes back in picocurines per liter, or pCi/L, the standard unit for radon measurement. We compare that number against the EPA action level of 4.0 pCi/L and, for homeowners who want the more conservative benchmark, the WHO reference level of 2.7 pCi/L.
What is the difference between a short-term and long-term radon test?
A short-term test runs 2 to 7 days under strict closed-house conditions and gives a quick reading. A long-term test runs 90 days to a year under normal living conditions and gives a seasonal average. Long-term is more accurate; short-term is faster.
Short-term test
Long-term test
Device
Charcoal canister or continuous radon monitor (CRM)
Alpha track detector
Duration
2 to 7 days
91 days to 1 year
Conditions
Closed-house protocol required (windows and doors shut, HVAC on normal settings)
Normal living conditions, no closed-house requirement
Best for
Real estate closings on a deadline, quick screening
Confirming true year-round exposure, deciding whether to install mitigation
Accuracy
Snapshot, can be skewed by weather or a single day’s conditions
Averages out seasonal swings, considered the gold standard
We offer both. If you need a fast answer for a closing, our Residential Radon Testing service covers short-term monitoring. If you want the fuller picture, or your short-term result landed in that gray zone around 4.0 pCi/L, the long-term test is the one that settles it.
How long does a long-term radon test actually take?
Minimum placement time is 91 days; many homeowners leave the detector in place for six months to a full year to capture every season. The detector itself takes maybe five minutes to set up. The waiting is the whole test.
We place the detector on a shelf or stand in the lowest livable area of the house, away from drafts, exterior walls, and moisture. You don’t need to do anything special while it’s running, just live in your house the way you normally would. When the placement period ends, we retrieve it and send it to the lab. Results typically take a few weeks to come back after the lab receives the detector.
When do you actually need a long-term test?
Most homeowners run a long-term test after an initial short-term result comes back elevated, or when they want a definitive baseline before deciding on mitigation. It’s also common for people who just moved into a Georgia home built on granite or gneiss bedrock and want to know what they’re dealing with across all four seasons.
Here’s when the calls actually come in:
A short-term test or a home inspection radon test came back close to 4.0 pCi/L, and the homeowner wants a firmer number before spending money on a mitigation system.
A family with kids or an aging parent in the home wants the most accurate read possible, not just a quick pass or fail.
Someone bought a house recently and skipped testing at closing, and now wants a proper Radon Level Assessment done right.
A homeowner is renovating a basement into a bedroom or living space and wants to know the air quality down there before finishing the room.
Someone had a mitigation system installed years ago and wants to confirm it’s still holding the level down over time, beyond the required 30-day post-mitigation check.
Which radon test is required when buying or selling a home in Atlanta?
Georgia doesn’t legally require a radon test to close on a home, but the Georgia Seller’s Property Disclosure Act, O.C.G.A. § 44-1-16, requires sellers to disclose known radon issues if they’re aware of them. Most buyers order a short-term test during the inspection period because closing timelines don’t allow for 90 days of waiting.
A long-term test isn’t practical during a real estate transaction with a tight closing date. But it’s exactly what we recommend once you own the home, especially if the short-term inspection result was borderline. Our Certified Radon Testing service covers both the quick pre-closing test and, once you’ve moved in, the longer follow-up test if you want a fuller picture.
How we run a long-term radon test in your home
We’re straightforward about what we do and don’t do at each step:
We walk the lowest level of your home with you and pick the right spot, at least 20 inches off the floor, away from drafts, exterior doors, and windows.
We place the alpha track detector and log the start date.
You live in your house normally. No closed-house rules, no schedule disruption.
At 91 days minimum (longer if you want a full-year average), we retrieve the detector.
The detector goes to a lab for analysis and we walk you through the pCi/L result against the EPA action level and the WHO reference level.
If the result comes back elevated, we talk through mitigation options honestly, including whether active sub-slab depressurization or a sub-membrane depressurization system makes more sense for your specific foundation.
There’s no guesswork about who’s coming into your home either. Our technicians follow ANSI/AARST radon testing standards and carry NRPP and NRSB certification, the two credentialing bodies that set the bar for this trade nationally.
Is radon really a problem in Atlanta given our warm climate?
Yes. Radon comes from bedrock, not weather, and most of metro Atlanta sits on granite and gneiss formations that produce it steadily regardless of season. Warm winters don’t lower radon risk the way people assume they might.
The EPA places much of North Georgia, including Fulton, Cobb, DeKalb, and Cherokee counties, in Radon Zone 1, the highest-risk category, because of this bedrock geology. Homes in Gordon, Pickens, Forsyth, and Hall counties sit on similar granite and gneiss formations. Radon seeps up through soil gas and enters homes through foundation cracks, sump pits, and slab penetrations no matter what the thermometer says outside.
What is the average radon level in Atlanta area homes?
We don’t have a single official average to quote you, and any business that gives you a precise citywide number without a study behind it is guessing. What we can tell you is that in Zone 1 counties like Fulton, Cobb, and DeKalb, elevated readings above 4.0 pCi/L are common enough that testing every home, especially ones with basements or slab foundations over granite bedrock, is worth doing rather than assuming you’re fine.
Why homeowners in metro Atlanta call us for this
We test and mitigate radon across Cobb, Hall, DeKalb, Fulton, Gordon, Newton, Clayton, Forsyth, and Pickens counties in Georgia. Our technicians hold NRPP and NRSB certification and follow ANSI/AARST protocols for both testing and mitigation, which is the standard homebuyers, inspectors, and real estate attorneys in Georgia expect to see on paperwork. We use alpha track detectors for long-term testing and continuous radon monitors for short-term work, and we’re upfront about which one fits your situation instead of upselling the longer test when you’re on a closing deadline.
If your long-term result does come back elevated, we don’t hand you off to someone else. We install active sub-slab depressurization systems, run PVC vent pipe to the roofline, and set a manometer so you can check the system’s working at a glance. Every mitigation job gets a post-mitigation verification test within 30 days, because a fan running isn’t proof of anything until the number confirms it.
Related radon services we also handle
A long-term test is often one step in a longer relationship with your home’s air quality. We also handle Residential Radon Testing for quick short-term checks, Certified Radon Testing for real estate transactions, and full Radon Level Assessment work that combines testing with a plain-language explanation of what your number means. If a test comes back high, we move into sub-slab depressurization or sub-membrane depressurization depending on whether your home has a basement, slab, or crawl space. All of this sits under our broader Environmental Health Service Services work in metro Atlanta.
Frequently asked questions
How long does radon mitigation installation take?
Most active sub-slab depressurization installs take about a day. The crew drills a suction point through the slab, runs PVC vent pipe to above the roofline, installs the inline fan, and sets a manometer so you can monitor pressure differential going forward.
What does a radon mitigation fan do and how long does it last?
The inline radon fan is the only moving mechanical part in the whole system. It pulls soil gas from beneath the slab through the suction pit and vents it above the roof before it can enter your living space. Fans are rated for continuous outdoor duty and are typically the one component that eventually needs replacing over the life of a system.
Should I get a radon test before closing on a home in Atlanta?
Yes. A short-term test during your inspection period is standard practice, even though Georgia law doesn’t mandate it. If the result lands close to the EPA’s 4.0 pCi/L action level, following up with a long-term test after you move in gives you a truer picture before deciding on mitigation.
Can I do a long-term test myself with a mail-in kit?
You can buy alpha track detectors online, but placement matters. Detectors placed too close to a window, an exterior wall, or a heating vent give skewed readings. Having a certified technician place it and interpret the pCi/L result against EPA and WHO benchmarks means you’re not left guessing what the number actually means for your house.
Do I need to keep windows and doors closed during a long-term test?
No. Closed-house conditions apply to short-term tests only. During a long-term test, you live normally, open windows in nice weather, run your HVAC as usual. That normal variation is exactly what gives you an accurate seasonal average instead of a one-week guess.
