Radon testing in Knoxville, TN
The state gives kits away free. Real-estate deals need certified tests on 48-hour clocks. Here’s which test you need, what it costs, and how the timeline works when a contract is ticking.
Radon testing in Knoxville runs from free to a few hundred dollars depending on the job: the Tennessee Radon Program mails free charcoal test kits to any resident (results in about a week), while real-estate transactions use a certified professional with a continuous radon monitor: a 48-hour test under closed-house conditions that produces an hour-by-hour report both sides of the deal can trust. Results at or above 4.0 pCi/L mean mitigate; 2.0–4.0 is the EPA’s “consider fixing” band. Knox and its neighboring counties sit in EPA Zone 1, and TDEC recommends every Tennessee home retest every two years regardless of past results.
Match the test to the situation.
Paying for the wrong test wastes money in one direction and credibility in the other. Five situations, five right answers:
| Your situation | The right test | Cost | Turnaround |
|---|---|---|---|
| Homeowner, just want to know | Free state charcoal kit (TDEC mails ~6,000 a year) | $0 | 2–7 day exposure + lab week |
| Buying a house, contingency in play | Certified pro with a continuous radon monitor (CRM), closed-house conditions | $150–$300 | 48 hours + same-day report |
| Selling, want no surprises | Same certified CRM test, done before you list | $150–$300 | 48 hours, on your schedule, not the buyer’s |
| Just mitigated | Independent verification test, not the installer’s own | kit cost–$200 | 48 hours–1 week |
| Known levels, want ongoing eyes | Consumer continuous monitor on a shelf | $150–$250 once | Live, forever |
Pro-test pricing shown as the typical bracket quoted in this market; we publish partner rates as the network comes aboard.
Radon in a Tennessee real-estate deal.
In East Tennessee, radon testing is standard practice in transactions, and Tennessee’s disclosure form requires sellers to disclose known radon. Here’s how the week actually goes:
Inspection period opens
The radon test gets ordered with the home inspection, same visit or the day after. Don’t wait; the contingency window doesn’t.
48 hours, doors closed
The monitor runs two full days under closed-house conditions: windows shut, HVAC normal. Tampering shows in the hourly data.
The number lands
Under 4.0: file it and move on. At or over: the buyer’s agent typically asks the seller to install mitigation before closing.
Fix on the clock
Mitigation installs in 1–2 days and verifies in 2 more, so a failed radon test almost never has to move a closing date. How the fix works.
Agents and inspectors: this timeline is yours to borrow. A co-branded version for client folders is coming with launch.
Why the test has rules, and why breaking them backfires.
The rules
Windows closed for 12 hours before and during. Exterior doors used only for coming and going. HVAC runs normally; no whole-house fans. The monitor sits in the lowest lived-in level, away from drafts and windows.
The why
Radon concentration swings with ventilation. Closed-house conditions measure the house the way winter does: the honest worst case you’d actually live in, not a breezy spring afternoon.
The backfire
Opening windows mid-test to game a transaction reads as a sawtooth in the hourly CRM data. Certified testers flag it, the test voids, and the deal gets a re-test plus a trust problem. The hourly log is the polygraph.
On a contract clock?
Certified 48-hour testing that buyers, sellers, and agents all accept, and mitigation on the same timeline if the result comes back high.
A real person answers, seven days a week
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Testing questions, straight answers
Is the free state kit actually any good?
Yes. It’s a real charcoal test analyzed at a real lab, and for a homeowner’s own knowledge it’s the best dollar you’ll never spend. Its limits are procedural, not scientific: it’s self-administered on the honor system, so it carries no weight in a transaction, and the multi-day mail-and-lab loop is too slow for a contingency window. Curiosity: free kit. Contract: certified CRM.
What reading means I need to act?
At or above 4.0 pCi/L: fix the house; that’s the EPA action level. Between 2.0 and 4.0: the EPA says consider fixing, and the World Health Organization would already have you acting at 2.7. Below 2.0: file it and retest in two years. One more honest note: a single short-term test is a snapshot, so confirm a surprising result with a second test before spending mitigation money.
When should I retest?
Every two years (TDEC’s standing recommendation for Tennessee homes), plus after any big change to the house: new HVAC, foundation or crawl space work, an addition, or finishing a lower level. And always after mitigation, independently. Houses change how they breathe; the rock underneath doesn’t send updates.
My crawl space is vented. Doesn’t that vent the radon too?
Less than you’d hope. Soil gas enters with pressure behind it, and the stack effect (warm air rising through your house like a chimney) pulls crawl space air up into the living space year-round. Vents dilute some radon in mild weather and matter least exactly when levels run highest, in a closed-up winter house. Knox County’s test average sits near the action level with all those vents open. Test the house, not the theory.
Where do I get the free kit?
The Tennessee Radon Program (TDEC) mails them to state residents at no cost, about 6,000 kits a year. Our step-by-step page with the request link and what to do with your result is coming with launch; until then, searching “Tennessee radon program free test kit” lands you on the tn.gov page in one hop.
Get the number. Then decide.
In a sale, an untested crawl space becomes the buyer’s leverage. Better to know your number before someone else does.
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