Two kinds of test
- Short-term tests run for two to four days. They give a quick reading and are the usual choice during a home sale.
- Long-term tests run for 90 to 365 days. Radon levels rise and fall with the seasons and the weather, so a long-term test gives a better picture of what you breathe across a year.
Where and how to place a test
The Department of Health's guidance for a home test:
- Test the lowest level of the home that people actually live in.
- Keep the device away from windows and exterior doors.
- Place it at least 20 inches above the floor.
- Close windows and doors 12 hours before the test starts, and keep them closed during a short-term test except for normal coming and going.
Who can test
In a private residence, a test can be done by the homeowner, a tenant, or a certified radon testing business. Rhode Island's radon regulation exempts people testing or mitigating a home they own or lease themselves from its licensing rules. Anyone testing for pay has to hold the right state credential, and the Department of Health publishes a list of certified testing businesses.
A certified business makes sense when the result has to be trusted by someone else: a buyer, a seller, a lender, or a tenant. It also makes sense after a mitigation system goes in. The Department of Health says testing should be performed after any radon mitigation work, and a test from a business other than the installer gives you an independent check. See mitigation.
Reading the result
Results are reported in picocuries per liter, written pCi/L.
- 4.0 pCi/L or higher: at or above the EPA action level. The EPA recommends fixing the home.
- Between 2 and 4 pCi/L: the EPA suggests considering a fix, since no level of radon is known to be completely safe.
- Below 2 pCi/L: no action recommended, but test again later.
If a short-term test comes back high, a second test is a reasonable next step before spending money, unless you're on a closing deadline.
When to test again
The Department of Health suggests retesting every three to five years, and after remodeling, since changes to a foundation, an addition, or a newly finished basement can change how radon moves through the house.
Buying a home? See radon and home sales. On a private well? See radon in well water.