Radon testing during a home inspection

If the home has not been tested, EPA says to make sure a test is done as soon as possible, and to consider contract provisions that settle the details first. Here is the sequence, built from EPA's guide.

1. 1

   Write the radon terms into the offer

   Where the test will be located, who should conduct it, what type of test, when, how results and costs are shared, and when mitigation will be done and who will pay.

2. 2

   Book the tester

   EPA says your state radon office can give you its approved list of radon testing companies. Book early; results are not instant.

3. 3

   Close the house

   For a short-term test of 2 to 4 days, EPA says closed-house conditions start at least 12 hours before the test and last the entire test.

4. 4

   Run the test

   For at least 48 hours, with one of EPA's three short-term options for a sale and steps to prevent or detect interference.

5. 5

   Get the report

   EPA says results come within a few days or weeks. If you need them quickly, ask how long they will take and request expedited service.

6. 6

   Decide and negotiate

   Compare the result with EPA's guidance levels, then settle the terms the contract left open.

Inspecting a newly built home

A new house still needs a radon number. EPA's guide tells buyers of a new home to ask if radon-resistant construction features were used and if the home has been tested, and says every new home should be tested for radon as soon as possible after occupancy, even if built to be radon-resistant. If a builder has installed a passive system, a high result means adding a fan, which EPA says can easily be done; see passive radon systems.

When does the radon test during a home inspection start?

It can start at the inspection visit, but the clock that matters is the closed-house clock. For a short-term test of 2 to 4 days, windows and outside doors are closed at least 12 hours before the device starts, so the occupants need notice before the inspector arrives. EPA says to give them written instructions and explain why proper testing conditions matter.

EPA's guide gives a buyer two routes: accept an earlier test result from the seller, or ask for a new test to be conducted by a qualified radon tester. Who arranges the new test is one of the points EPA suggests the contract settle.

Booking the home inspection radon test

• Ask for the radon test by name, separately from the general inspection.
• Ask for the credential, and confirm it with the body that issued it. Your state radon office can tell you which credentials your state accepts.
• Ask which laboratory analyzes the device. EPA says to use a device from a qualified laboratory.
• Ask how interference will be prevented or detected, and whether the occupants will sign a non-interference agreement.

Home inspector radon testing equipment

EPA sorts test devices into two groups. Passive devices need no power: charcoal canisters, alpha-track detectors, charcoal liquid scintillation devices and electret ion chamber detectors, which go to a lab after exposure. Active devices need power: continuous radon monitors and continuous working level monitors, which record levels throughout the test and can reveal unusual swings. EPA says some active devices are designed to deter and detect interference and, though they may cost more, may ensure a more reliable result. See continuous radon monitors.

The report is what the negotiation rests on, so read all of it. EPA's guide says what a reliable one should let you check.

• The result, as an average. For two passive tests, EPA's decision rule uses the average of the two. For a continuous monitor, the average radon level.
• Start and stop times and the test location. EPA's checklist asks for these to be recorded.
• The tester's ID. EPA says the tester's ID number, if available, should be included or noted in the test report.
• The hourly record, for a monitor. EPA's Consumer's Guide says active devices usually provide hourly readings and an average result, and the buyer and seller guide says such a report can reveal unusual swings. A qualified tester can explain it.
• Evidence conditions held. EPA says you or the tester should be able to demonstrate that testing conditions were not violated.

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2 pCi/L

4 pCi/L

00 Bq/m³274 Bq/m³4148 Bq/m³6222 Bq/m³8296 Bq/m³10+370 Bq/m³

• 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.

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. For context, EPA estimates the average indoor level at about 1.3 pCi/L. Check a report's number in the radon result interpreter, or read how to read a radon test.

Results near 4 pCi/L

EPA says short-term tests are less definitive when results are close to 4 pCi/L. Its example: an average of 4.1 pCi/L from two short-term tests means about a 50 percent chance that the year-round average is somewhat below, or above, 4 pCi/L. EPA also says any radon exposure carries some risk, so a result just under 4 is not a reason to stop reading.

EPA does not say who pays. It says the contract should state when radon mitigation measures will be taken, and who will pay for them. A contract that already answers that turns a high result into a schedule rather than a dispute.

Home inspection high radon: what to settle in writing

EPA's Consumer's Guide says a post-mitigation test should be done within 30 days of system installation, but no sooner than 24 hours after the system is in operation. Where radon problems have been fixed, EPA says, home sales have not been blocked. More in buying a house with radon and how mitigation cost works.

EPA says there is a potential for test interference in real estate transactions. A result you cannot trust helps neither side.

Asking for another test

EPA's checklist is blunt: if the seller or qualified tester cannot confirm that all items have been completed, take another test. Signs to look for in the report are the ones EPA's precautions are built to catch: unusual swings in a monitor's readings, a device that was moved, or temperature and pressure records that suggest opened windows or storms. EPA also says not to run tests shorter than four days during severe storms or high winds.

A second short-term test can run immediately after the first, with an identical device in the same place; that is one of EPA's three sale options. See what can affect a radon test.

Usually it is a choice, not a mandate, and the requirement, where there is one, comes from the contract or the place. EPA's advice is a recommendation: if you are buying or selling a home, have it tested for radon. Testing and disclosure rules vary by state, and a buyer may ask for a new test if the state or local government requires disclosure of radon information to buyers.

So the practical answer for a buyer is to ask for the radon test by name and put it in the offer, saying what result triggers the clause and what happens next, not only that a test will take place. Your state radon program can say whether anything more applies where the home is, and radon disclosure lists the disclosure rules state programs publish.

EPA's guide accepts any of three short-term options for deciding, in a sale, whether the home should be fixed. Which one the tester uses changes the timeline you write into the contract.

EPA describes the trade-off: two tests taken at the same time (simultaneous) would improve the precision of the radon test, while one test followed by another (sequential) would most likely give a better representation of the seasonal average. A sequential pair takes at least twice as long as one test. EPA adds that both active and passive devices may have features which help to prevent test interference, and that your state radon office can help you decide which option is best.

The seller's household runs the test conditions, so their part decides whether the result holds up. EPA's Radon Testing Checklist sets out what happens before, during and after.

Closed-house conditions mean keeping all windows closed, keeping doors closed except for normal entry and exit, and not operating fans or other machines which bring in air from outside. Fans that are part of a radon-reduction system, or small exhaust fans run only for short periods, may run during the test. Showings can go on, since normal entry and exit is allowed, but agents should leave the device alone.

A sale test answers one question at one time. EPA's guides name the moments when a new owner should measure again, and several come in the first years after closing.