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 10.5 pCi/L, based on Airthings measurements across 37 cities.

Updated August 16, 2026

Highest city

10.5pCi/L

Spirit Lake

Idaho city average

3.8pCi/L

across 37 cities

Above action level

13/ 37

cities

Idaho Cities Ranked by Indoor Radon Levels
#	Location	Avg level	Monitors	vs action level
1	Spirit Lake	10.5 pCi/L	16	2.6× over
2	Driggs	7.9 pCi/L	21	2.0× over
3	Mountain Home	7.6 pCi/L	6	1.9× over
4	Rexburg	7.5 pCi/L	17	1.9× over
5	Hayden	7.0 pCi/L	37	1.8× over
6	Post Falls	7.0 pCi/L	46	1.7× over
7	Sandpoint	6.3 pCi/L	34	1.6× over
8	Hailey	4.9 pCi/L	22	1.2× over
9	Rathdrum	4.9 pCi/L	8	1.2× over
10	Coeur d'Alene	4.7 pCi/L	37	1.2× over
11	Ponderay	4.0 pCi/L	8	1.0× over
12	Rigby	4.0 pCi/L	14	1.0× over
13	Moscow	4.0 pCi/L	11	1.0× over
✓ Below EPA action level (4 pCi/L)
14	Victor	4.0 pCi/L	17	1.0× under
15	Ketchum	4.0 pCi/L	33	1.0× under
16	Twin Falls	3.6 pCi/L	13	0.9× under
17	Sun Valley	3.5 pCi/L	28	0.9× under
18	Pocatello	3.5 pCi/L	23	0.9× under
19	Dalton Gardens	3.5 pCi/L	23	0.9× under
20	Iona	3.4 pCi/L	9	0.8× under
21	Bellevue	3.0 pCi/L	9	0.8× under
22	Idaho Falls	3.0 pCi/L	37	0.7× under
23	Shelley	2.9 pCi/L	10	0.7× under
24	Garden City	2.6 pCi/L	39	0.7× under
25	Boise	2.6 pCi/L	137	0.7× under
26	McCall	2.6 pCi/L	27	0.7× under
27	Lincoln	2.2 pCi/L	11	0.6× under
28	Ammon	2.2 pCi/L	14	0.5× under
29	Bonners Ferry	2.1 pCi/L	7	0.5× under
30	Eagle	1.8 pCi/L	60	0.5× under
31	Meridian	1.8 pCi/L	74	0.4× under
32	Kuna	1.6 pCi/L	15	0.4× under
33	Nampa	1.5 pCi/L	20	0.4× under
34	Middleton	1.4 pCi/L	16	0.4× under
35	Filer	1.4 pCi/L	7	0.3× under
36	Plummer	1.1 pCi/L	7	0.3× under
37	Star	0.8 pCi/L	12	0.2× under