Home Buyer's and Seller's Guide to Radon is a publication by the Environmental Protection Agency. Used with permission under public domain and creative commons. Usage: Category Education; License: Creative Commons Attribution license (reuse allowed)
On this page: d. Length of Time to Test.
Because radon levels tend to vary from day to day and season to season, a short-term test is less likely than a long-term test to tell you your year-round average radon level. However, if you need results quickly, a short-term test may be used to decide whether to fix the home.
There Are Two General Ways to Test Your Home for Radon:
The quickest way to test is with short-term tests. Short-term tests remain in your home from two to 90 days, depending on the device. There are two groups of devices which are more commonly used for short-term testing. The passive device group includes alpha track detectors, charcoal canisters, charcoal liquid scintillation detectors, and electret ion chambers. The active device group consists of different types of continuous monitors.
Long-Term TestingLong-term tests remain in your home for more than 90 days. Alpha track and electret ion chamber detectors are commonly used for this type of testing.
A long-term test result is more likely to tell you your home's year-round average radon level than a short-term test. If time permits (more than 90 days), long-term tests can be used to confirm initial short-term results. When long-term test results are 4 pi/L or higher, EPA recommends fixing the home.
Whether you test for radon yourself or hire a qualified tester, all radon tests should be taken for a minimum of 48 hours. Some devices require a longer (minimum) length of time, e.g., a 7-day charcoal canister device.