Short answer
A radon test takes at least 48 hours. Short-term tests stay in the home from 2 to 90 days, depending on the device, and long-term tests more than 90 days; a lab result then comes back within a few days or weeks of mailing the device.
Next step: pick the right test for your home. Which test to use
Most people start with a short-term kit of a few days. Some devices have a longer minimum, such as a 7-day charcoal canister, and for a test of 2 to 4 days the house is closed for at least 12 hours before it starts and for the whole test.
A longer test gives a truer picture, because radon levels vary from day to day and season to season. A
What to do next: pick a
In a picture · 1 min read
The length depends on the kind of test and on the device. Every radon test should run at least 48 hours.
| Test | How long it runs | What it is for |
|---|---|---|
| Short-term test | Stays in the home from 2 to 90 days, depending on the device, and for a minimum of 48 hours. | A faster screening result. Because radon levels vary from day to day and season to season, it is less likely than a long-term test to tell you the year-round average. |
| Long-term test | Stays in the home for more than 90 days. | It is more likely than a short-term test to tell you the home's year-round average radon level. |
| Continuous monitor | Logs readings for the whole test, run as a short-term or a long-term test under the same durations in EPA guidance. | Logs a graph over time, so you can see trends and spot anomalies rather than a single number. |
| Test | How long it runs | Typical devices |
|---|---|---|
| Short-term, 2 to 4 days | At least 48 hours; the house is closed 12 hours before and throughout | Charcoal canisters, charcoal liquid scintillation, electret ion chambers, continuous monitors |
| Short-term, 4 to 7 days | Closed-house conditions kept for the whole test | Some charcoal canisters have a 7-day minimum |
| Short-term, up to 90 days | Up to 90 days, depending on the device | Alpha track and electret detectors |
| Long-term | More than 90 days | Alpha track and electret detectors |
At a glance · 1 min read
Radon levels move. They vary from day to day and season to season, and within a building even from hour to hour; rain or snow, barometric pressure and other influences push them up and down. A short test catches a slice of that, so it is less likely than a long-term test to show the year-round average. The longer the test, the better the result reflects the home and how you live in it, and a measurement of at least three months is the better estimate of a home's annual mean.
| If you need | Choose | Why |
|---|---|---|
| An answer quickly | A short-term test | It is the quickest way to test, and a short-term result can be used to decide whether to fix |
| The year-round average | A long-term test | A long-term result is more likely to reflect the home's year-round level |
| Both | Short-term first, then long-term | If time permits, a long-term test can confirm an initial short-term result |
Step by step · 1 min read
Step 1 of 4:
Record the times
Write down the start and stop dates and times; the lab needs them.
Step 2 of 4:
Mail it right away
Reseal the package and send it to the lab named on it as soon as the test ends.
Step 3 of 4:
Wait for the lab
Results usually come back within a few days or weeks. If you are in a hurry, ask how long results take and whether expedited service is available.
Step 4 of 4:
Or use a monitor
A continuous monitor measures and records radon as it goes, and a qualified tester can explain its report.
In a picture · 1 min read
Real estate testing is built around the deadline of a sale, so it uses short-term tests of at least 48 hours, in one of three ways.
If you are testing in a real estate transaction and you need results quickly, any of the following three options for short-term tests are acceptable in determining whether the home should be fixed.
Option 1. Two tests at the same time
PassiveTake two short-term tests at the same time in the same location for at least 48 hours.
What to do nextFix the home if the average of the two tests is 4 pCi/L or more.
Two tests taken at the same time (simultaneous) would improve the precision of this radon test.
Option 2. One test, then a second
PassiveTake an initial short-term test for at least 48 hours. Immediately upon completing the first test, do a second test using an identical device in the same location as the first test.
What to do nextFix the home if the average of the two tests is 4 pCi/L or more.
One test followed by another test (sequential) would most likely give a better representation of the seasonal average.
Option 3. A continuous monitor
ActiveTest the home with a continuous monitor for at least 48 hours.
What to do nextFix the home if the average radon level is 4 pCi/L or more.
Both active and passive devices may have features which help to prevent test interference.
Any real estate test for radon should include steps to prevent or detect interference with the test device. Your state radon office can help you decide which option is best.
After a
Questions · 1 min read
No. Every radon test should run at least 48 hours, and some devices need longer.
A test of at least 48 hours gives a usable short-term result, and a high one is confirmed with a second test. Tests of just 2 or 3 days should not be run during unusually severe storms or high winds.
From a lab, usually a few days or weeks after you mail the device. A continuous monitor records as it goes, and the tester analyzes the data and reports the result.
More than 90 days. A test of at least three months is the better estimate of the year-round average.
At least 48 hours, with one of the three real estate options: two tests side by side, one test followed by another, or a continuous monitor. See should I get a radon test with my home inspection.
Follow the package: leave it in place for as long as it says, record the stop time and mail it right away. For a longer measurement, use a long-term test, which runs more than 90 days.
How a radon test works, who can run one, and how to read the number it gives you.
How a professional radon test works, what it proves and whether it is worth it.
Read the guideWhat counts as high and how to bring them down.
Read the guideEPA's action level, WHO's reference level and what counts as acceptable.
Read the guide