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Can a radon test be manipulated?

By Radon411 Editorial TeamUpdated How we research

Short answer

Yes, a short-term radon test can be thrown off by opening windows, running fans that pull in outside air, or moving the device, but that changes the reading, not the radon. Such interference can invalidate the result and is illegal in some states, and testers use monitors, seals and agreements to detect it.

Next step: pick the right test for your home. Which test to use

Disturbing or interfering with the test device, or with , can invalidate the test results and is illegal in some states. Testers prevent or detect interference with devices that record unusual swings, tamper-proof window seals, a signed non-interference agreement and other checks.

A lowered reading does not lower the radon: once windows are closed, levels most often return to where they were within about 12 hours.

What to do next: run the test by the testing checklist, and if the level is high, fix the house rather than the number.

How a radon test gets thrown off

A short-term radon test is only valid under : all windows closed, doors closed except for normal entry and exit, and no fans or other machines bringing in air from outside. Breaking those conditions, or moving the device, changes the reading without changing the house.

Common ways a test is disturbed, and what each does
What happensEffect on the readingWhy it does not last
Windows or doors left openOutdoor air dilutes indoor air while they stay openOnce they are closed, levels most often return to where they were within about 12 hours
Fans that bring in outside airThe same dilution, while they runNot allowed during a short-term test; a radon system's own fan or brief small exhaust fans may run
Device moved, covered or handledThe sample no longer reflects the roomThe device should not be disturbed at any point during the test
Any of the aboveA result that does not describe the homeInterfering with the device or closed-house conditions can invalidate the result and is illegal in some states

The radon is still there. A reading lowered by an open window describes a few days of unusual air, not the year the next occupant will breathe. That is why every radon test, and especially one in a home sale, should include steps to prevent interference.

How testers detect interference

Interference is a known risk in real estate transactions, and testers have a set of ways to prevent or detect it.

Ways to prevent or detect test interference
MethodWhat it catches
A device that frequently records radon or decay productsUnusual swings in the level during the test
A motion detectorWhether the device was moved or testing conditions changed
A proximity detectorPeople in the room, which may line up with changes in the level
Barometric pressure recordsWeather that may have affected the test
Temperature recordsWhether doors and windows were opened
Tamper-proof seals on windowsWhether closed-house conditions held
A signed non-interference agreementThe seller's or occupant's commitment not to interfere

Devices differ in how hard they are to fool. Some passive devices resist interference better than others, and some active monitors are designed specifically to deter and detect it, with reports that show unusual or abnormal swings during the test.

What happens when a test is compromised

A disturbed test does not count. If the seller or tester cannot confirm that every item on the testing checklist was completed, the answer is another test, and either party should be able to show that testing conditions were not violated. A good tester tells the occupants plainly that a reliable result depends on their cooperation, because interference with the test or with closed-house conditions will invalidate it.

EPA's three short-term radon testing options for a real estate transaction: two tests at the same time, one test then a second, or a continuous monitor, each for at least 48 hours, with what to do after each.
Read this figure as text

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.

  1. Option 1. Two tests at the same time

    Passive

    Take 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.

  2. Option 2. One test, then a second

    Passive

    Take 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.

  3. Option 3. A continuous monitor

    Active

    Test 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.

The three short-term testing options for a home sale; any of them should include steps to prevent or detect interference.

Put the testing in the contract: where the test goes, who conducts it, what type, when, how buyer and seller share the results and costs, and when happens and who pays. State disclosure rules are in the radon disclosure guide.

The honest way to a lower number

The only lasting way to a lower result is a lower radon level. Radon in most homes can be brought to 2 or below, even very high levels can be reduced to acceptable levels, and it is better to fix a radon problem before a home goes on the market, while there is time.

For sellers and buyers, what to do instead
If you areWhat to do
SellingTest now and keep the results; if the level is high, fix it before you sell. Where radon problems have been fixed, sales have not been blocked
BuyingBuyers often want the test done by someone not involved in the sale, and an independent, qualified tester for the check after mitigation
Using one firm to test and fixBe aware of the potential conflict of interest; some states may require the homeowner to sign a waiver

How a fix works is covered in how to reduce radon; buying a home that already has one is in should I buy a home with a radon mitigation system.

Questions about manipulating radon tests

How do you lower radon levels for a test?

By lowering the radon, which means a mitigation system. Ventilating the house during a test only changes the reading while the air is open, and interfering with closed-house conditions can invalidate the result and is illegal in some states.

Does opening windows before a radon test lower the result?

It is not allowed. For a 2- to 4-day test, windows and outside doors stay closed for at least 12 hours before the test and throughout it. Once windows are closed again, levels most often return to where they were within about 12 hours.

Can a seller tamper with a radon test?

They can try, which is why testers use monitors that record swings, motion detectors, window seals and a signed non-interference agreement.

Can a continuous monitor tell if windows were opened?

It can show the signs. Active monitors reveal unusual or abnormal swings during the test, and a temperature record helps show whether doors and windows were opened.

What happens if a radon test was tampered with?

It should be repeated. If every checklist item cannot be confirmed, take another test; interference invalidates the result.

Who should do the radon test in a home sale?

Buyers often want a test by someone who is not involved in the sale, and independent, qualified testers are recommended. See should I get a radon test with my home inspection.

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