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What is radon testing?

By Radon411 Editorial TeamUpdated How we research

Short answer

Radon testing is measuring the radon concentration in a building's air over a set period, with a detector that is either analyzed by a laboratory afterward or reports the result itself. It is the only way to know the level in a specific building, because a map or a neighbor's result describes somewhere else.

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

Tests are grouped by length. stay in place from 2 to 90 days, every test runs at least 48 hours, and for a short-term test the windows and outside doors are closed at least 12 hours before it begins. run more than 90 days and give a better picture of the year-round average, because radon levels tend to vary from day to day and season to season.

There are two categories of testing: one for homeowners whose home is not for sale, and one for real estate transactions, which uses three short-term options with steps against interference. A homeowner's test goes in the lowest lived-in level, at least 20 inches above the floor, away from drafts, high heat, high humidity and exterior walls. Passive devices are sent to a laboratory afterward; active devices such as continuous monitors measure and record radon themselves.

You can test with a do-it-yourself kit or hire a qualified measurement professional. Either way the result is reported in (pCi/L).

What to do next: read the testing guide, pick a kit or find a measurement professional, and use the interpreter once you have a number. If a single short-term result is high, take a follow-up test before deciding on a fix.

What radon testing is for

Radon testing answers one question: how much radon is in the air of this building. You cannot see or smell radon, so special equipment is needed to detect it, and levels vary so much from home to home that a map, a zone or a neighbor's result cannot stand in. Testing is the only way to know.

Who should test, and when
WhoWhen
Every home below the third floorAt least once; testing is recommended for all of them
Homes never tested, or with an unknown levelNow
Buyers and sellersDuring the sale
Owners planning renovationsBefore and after the work
Homes with a radon systemAfter it is installed and at least every two years
SchoolsTesting is recommended there too

Testing is easy and takes only a few minutes of your own time, and millions of Americans have already tested their homes.

The two kinds of radon testing

There are two categories of radon testing. One is for homeowners and occupants whose home is not for sale; the other is for real estate transactions, where the guidance is adjusted for the tight timing of a sale and the risk of interference.

Testing your own home and testing for a sale
AspectYour own homeA home sale
Usual first stepOne short-term test in the lowest lived-in levelOne of three short-term options, each at least 48 hours
If the result is highA follow-up test: long-term, or a second short-termThe options already build in two measurements or a continuous record
Who usually testsThe homeowner with a kit, or a qualified testerA qualified tester, very often a home inspector
InterferenceKeep the house closed and leave the device aloneSteps to prevent or detect interference are part of the test
Flowchart of EPA's radon testing steps: take a short-term test; at or above 4 pCi/L follow up with a long-term or a second short-term test; then fix the home or consider fixing based on the result or the average of the two tests.
Read this figure as text

  1. 1Step 1: Take a short-term test.

    • Below 4 pCi/LEven if your test result is below 4 pCi/L, you may want to test again sometime in the future.
    • At or above 4 pCi/LIf your result is at or above 4 pCi/L, take a followup test to be sure.

  2. 2Step 2: Follow up with either a long-term test or a second short-term test.

    • Long-term testFor a better understanding of your year-round average radon level, take a long-term test.
    • Second short-term testIf you need results quickly, take a second short-term test. If your first short-term test result is more than twice EPA's 4 pCi/L action level, you should take a second short-term test immediately.

  3. 3Step 3: Decide whether to fix your home.

    • After a long-term testFix your home if your long-term test result is 4 pCi/L or more.
    • After a second short-term testConsider fixing your home if the average of your first and second test is at or above 4 pCi/L.
The testing steps for your own home: a short-term test, a follow-up if it is high, then a decision.

Short-term and long-term testing

Table comparing a short-term radon test, a long-term radon test and a continuous radon monitor: how long each runs and what each is for.
Read this figure as text
TestHow long it runsWhat it is for
Short-term testStays 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 testStays 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 monitorLogs 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.
Short-term tests, long-term tests and continuous monitors.

stay in the home from two days to 90 days, depending on the device, and more than 90 days; every test runs at least 48 hours. Passive devices are exposed for a set time and sent to a laboratory, while active devices need power and usually give hourly readings and an average for the test period. Because levels vary from day to day and season to season, the longer the test, the better it reflects the home. The devices themselves are described in what is a radon test.

Who does radon testing

You can test your own home with a low-cost kit from a hardware store or by mail, or hire a qualified tester, which is the recommended route for a home sale. Your state radon office can give you a list of qualified testers, and private radon proficiency programs keep lists of certified professionals.

Checking a tester's qualifications
CheckWhy
State license, certification or registrationMany states require radon professionals to have one
A proficiency or certification credentialIn states that do not regulate radon services, ask for one; members usually carry a photo ID card with an expiration date
Formal trainingAsk whether they completed a course in radon measurement
The state's testing protocolSome states require testers to follow a specific protocol

A qualified tester also gives you an independent result, which matters in a sale. Find one in the measurement professionals directory, or compare doing it yourself in can I test for radon myself.

What testing reports

A radon test reports a concentration in of air (pCi/L). The national average indoor level is about 1.3 pCi/L, by EPA's estimate. The number is then read against the two guidance levels.

Scale of radon levels from 0 to 10 pCi/L marking EPA's 2 pCi/L level, where EPA says to consider fixing, and its 4 pCi/L action level, where EPA says to fix the home, with each mark also in Bq/m³.
Read this figure as text
  • Below 2 pCi/L (below 74 Bq/m³)Below both of EPA's guidance levels.
  • 2 to 4 pCi/L (74 Bq/m³ to 148 Bq/m³)EPA recommends considering a fix when the level is between 2 and 4 pCi/L.
  • At or above 4 pCi/L (148 Bq/m³ and up)EPA recommends fixing a home when the radon level is 4 pCi/L or higher.
The two guidance levels a result is read against, in pCi/L and Bq/m3.

EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Testing measures the building, not a person: radon in the body is not detectable by routine medical tests, and exposure is estimated from the air. See how to read a radon test.

Questions about radon testing

Why do a radon test?

Because there is no other way to know. Radon cannot be seen or smelled, and levels vary greatly between homes, so testing is the only way to learn yours.

Is radon testing necessary?

Testing is recommended for all homes below the third floor. See should I test for radon.

What is the difference between a radon test and radon testing?

A radon test is the device; radon testing is the whole process of placing it, keeping the house closed, sending it off and reading the result. See how to test for radon.

Can I do radon testing myself?

Yes, with a do-it-yourself kit for your own home. For a home sale, a qualified tester is recommended.

How long does radon testing take?

At least 48 hours for a short-term test, and more than 90 days for a long-term one. See how long does a radon test take.

Where can I get radon testing done?

Buy a kit from a hardware store, online or by mail, look for free or discounted kits from your state, or hire a qualified tester through your state radon office or the professionals directory.

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