When a home is due for a test
Radon offers the senses nothing: no smell, no taste, no haze in the basement air. And it ignores property lines: the house next door can read triple yours, or a third of it, because the gas follows soil seams and foundation quirks. So there’s no inferring your way to an answer. There’s only measuring.
Four moments put testing on the calendar. A home that has never been tested, which is most of the backlog in this state. A remodel or foundation change, like finishing a basement or adding drain tile, since anything that changes how the house touches the soil can change the number. Buying or selling, where the inspection window makes testing standard practice and the home-sales guide covers the rules. And after mitigation, where a test is how a system proves it worked, plus every couple of years after to confirm it still does.
None of these require a professional by law. Some benefit from one. The rest of this guide sorts out which is which.
Three ways to get a number
Store-bought kit
- Good for
- A first screen, low cost
- Keep in mind
- Instructions make or break it
Continuous monitor
- Good for
- Home sales, fast decisions
- Keep in mind
- Professionally placed and reported
Long-term test
- Good for
- The true annual average
- Keep in mind
- Takes 90 days or more
| Approach | Good for | Keep in mind |
|---|---|---|
| Store-bought kit | A first screen, low cost | Instructions make or break it |
| Continuous monitor | Home sales, fast decisions | Professionally placed and reported |
| Long-term test | The true annual average | Takes 90 days or more |
Any result at or above the EPA action level of 4 pCi/L deserves follow-up, whichever device produced it.
How a test actually runs
Every credible short-term test runs under closed-house conditions: exterior doors and windows stay shut for 12 hours before the test starts and for its whole duration. Normal coming and going through doors is fine. The point is to stop outdoor air from watering down the sample. An open-window test flatters the house and wastes the fee.
Placement does real work too. The device goes in the lowest level people regularly use (a basement family room, not a crawlspace nobody enters), a couple of feet off the floor, away from drafts, exterior walls, and humid rooms like baths. A kit on the furnace-room floor by the sump pit isn’t measuring what your family breathes.
On devices: store kits are legitimate. Follow the instructions carefully, mail promptly, and a charcoal kit gives an honest screen for little money. Professional testing earns its keep where stakes or standards rise: real-estate transactions, where continuous monitors with hourly logs and tamper flags are the norm, and confirmations before someone spends real money on mitigation.
Retesting is standard practice, not paranoia: confirm any near-the-line result before acting, retest after mitigation to verify the drop, and re-check every few years, because houses settle, fans age, and numbers drift.
Rather have it done right the first time? Schedule it
Where the result points
A number below the action level closes the loop. Keep the report with the house documents, because a future buyer’s agent will ask, and put a reminder a few years out.
A number at 4 picocuries per liter or above starts the second half of the story. Confirm it if it’s borderline and time allows, then fix it: radon mitigation collects the gas under the house, vents it above the roof, and gets verified by exactly the kind of retest this guide describes.
If the test is happening inside a purchase or sale, protocol matters as much as the number: who tests, what device, what the other side will accept. That’s covered in radon and home sales.
And if you’d rather hand the whole thing off — placement, conditions, lab, report — professional testing is a scheduled visit and a written number. Either path beats the test kit that sits in a drawer for a year. The house has an answer already. The only question is when you collect it.