Short answer
A long-term test is a radon test that stays 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.
What long-term test means
EPA says alpha track and electret detectors are commonly used for this type of testing. Nebraska's radon program describes the usual run as 3 months to 1 year, which gives a better average because it takes in the seasons.
CDC puts the point in one line: long-term kits tell you your home's year-round average level.
How much more air time a long-term test gets
Each row multiplies days by 24 and divides by the 48-hour minimum.
| Test | Days | Hours sampled | Times the 48-hour minimum |
|---|---|---|---|
| The 48-hour minimum | 2 | 48 | 1 |
| The shortest long-term test | 91 | 2,184 | 45.5 |
| A full year | 365 | 8,760 | 182.5 |
What it means for your home
Choose a long-term test when nothing is pressing. EPA's own words: for a better understanding of your year-round average radon level, take a long-term test.
It is not the test for a rush. If a first short-term result is more than twice EPA's
Where to go next
- Which radon test to use. See whether a long-term test or a short one fits your situation.
- Short-term and long-term radon test kits compared. What each kind costs, how long it takes and what its result can tell you.