Idaho Cities Ranked by Indoor Radon Levels
Measured averages from Airthings devices across Idaho, USA. Action level: 4 pCi/L — the threshold at which remediation is recommended.
Spirit Lake has the highest measured indoor radon in Idaho at 10.1 pCi/L, based on Airthings measurements across 44 cities.
Updated October 19, 2026
Highest city
10.1pCi/L
Spirit Lake
Idaho city average
3.8pCi/L
across 44 cities
Above action level
16/ 44
cities
| # | Location | Avg level | vs action level |
|---|---|---|---|
| 1 | Spirit Lake | 10.1 pCi/L | 2.5× over |
| 2 | Priest River | 8.6 pCi/L | 2.1× over |
| 3 | Driggs | 7.7 pCi/L | 1.9× over |
| 4 | Rexburg | 7.5 pCi/L | 1.9× over |
| 5 | Hayden | 7.0 pCi/L | 1.8× over |
| 6 | Post Falls | 6.6 pCi/L | 1.7× over |
| 7 | Mountain Home | 6.6 pCi/L | 1.6× over |
| 8 | Sandpoint | 6.2 pCi/L | 1.5× over |
| 9 | Rathdrum | 5.5 pCi/L | 1.4× over |
| 10 | Salmon | 5.4 pCi/L | 1.3× over |
| 11 | Coeur d'Alene | 4.6 pCi/L | 1.1× over |
| 12 | Hailey | 4.5 pCi/L | 1.1× over |
| 13 | Dalton Gardens | 4.3 pCi/L | 1.1× over |
| 14 | Idaho City | 4.2 pCi/L | 1.0× over |
| 15 | Rigby | 4.0 pCi/L | 1.0× over |
| 16 | Moscow | 4.0 pCi/L | 1.0× over |
| ✓ Below EPA action level (4 pCi/L) | |||
| 17 | Ketchum | 3.9 pCi/L | 1.0× under |
| 18 | Challis | 3.9 pCi/L | 1.0× under |
| 19 | Ponderay | 3.9 pCi/L | 1.0× under |
| 20 | Victor | 3.8 pCi/L | 1.0× under |
| 21 | Pinehurst | 3.7 pCi/L | 0.9× under |
| 22 | Twin Falls | 3.6 pCi/L | 0.9× under |
| 23 | Pocatello | 3.6 pCi/L | 0.9× under |
| 24 | Sun Valley | 3.5 pCi/L | 0.9× under |
| 25 | Iona | 3.3 pCi/L | 0.8× under |
| 26 | Idaho Falls | 3.2 pCi/L | 0.8× under |
| 27 | Bellevue | 3.0 pCi/L | 0.8× under |
| 28 | McCall | 2.6 pCi/L | 0.7× under |
| 29 | Shelley | 2.6 pCi/L | 0.6× under |
| 30 | Garden City | 2.5 pCi/L | 0.6× under |
| 31 | Boise | 2.5 pCi/L | 0.6× under |
| 32 | Lincoln | 2.3 pCi/L | 0.6× under |
| 33 | Bonners Ferry | 2.2 pCi/L | 0.6× under |
| 34 | Ammon | 2.2 pCi/L | 0.5× under |
| 35 | Paris | 2.0 pCi/L | 0.5× under |
| 36 | Eagle | 1.8 pCi/L | 0.5× under |
| 37 | Meridian | 1.7 pCi/L | 0.4× under |
| 38 | Kuna | 1.6 pCi/L | 0.4× under |
| 39 | Nampa | 1.5 pCi/L | 0.4× under |
| 40 | Middleton | 1.4 pCi/L | 0.4× under |
| 41 | Filer | 1.4 pCi/L | 0.3× under |
| 42 | Caldwell | 1.1 pCi/L | 0.3× under |
| 43 | Plummer | 1.1 pCi/L | 0.3× under |
| 44 | Star | 0.8 pCi/L | 0.2× under |