ResourcesGlossary: units and levels
Action level
Short answer
The action level is the radon level at which EPA recommends fixing a home: 4 pCi/L, which is 148 Bq/m³. It is a point to act at, not a line with safety on one side.
What action level means
EPA recommends fixing a home when one
Other countries set their own figure. WHO proposes a reference level of 100
A result read against the action level
Each row divides a result by 4 and converts it to Bq/m³.
| Result, pCi/L | In Bq/m³ | Times the action level | What EPA says |
|---|---|---|---|
| 1.3 | 48.1 | 0.33 | The average indoor level |
| 2 | 74 | 0.5 | Consider fixing between 2 and 4 pCi/L |
| 4 | 148 | 1 | Fix the home |
| 4.1 | 151.7 | 1.025 | As the average of two short-term tests: about a 50 percent chance the year-round average is somewhat below, or above, 4 pCi/L |
| 8 | 296 | 2 | A first short-term result above this: take a second short-term test immediately |
What it means for your home
Hold a single short-term result loosely. Radon levels vary from day to day and season to season, which is why EPA's decision to fix rests on a long-term test or on two short-term tests averaged.
When the follow-up confirms a high level, the usual fix is a vent pipe and fan that pull radon from beneath the house. EPA says some systems reduce radon by up to 99 percent.
Where to go next
- Radon level interpreter. Enter your result and see which side of the action level it falls on.
- EPA radon guidance: action level, map and guides. EPA's testing steps in order, from the first test to the fix.