Highest Radon Risk ZIP Codes in Colorado — 2026

Out of 602 ZIP codes with data in Colorado, these are the lowest-ranked areas for radon zone. See also: National ZIP Codes with Highest Radon Risk | All Colorado Rankings

Statistic	Value
ZIP codes ranked	602
Lowest value	Zone 1 (High)
Median value	Zone 1 (High)
State	Colorado

100 Lowest-Ranked ZIP Codes

Rank	ZIP Code	City	State	Radon Zone	Safety Score
1	80550	Windsor	CO	Zone 1 (High)	31/100
2	80260	Denver	CO	Zone 1 (High)	33/100
3	80537	Loveland	CO	Zone 1 (High)	33/100
4	80817	Fountain	CO	Zone 1 (High)	33/100
5	81435	Telluride	CO	Zone 1 (High)	33/100
6	80651	Platteville	CO	Zone 1 (High)	34/100
7	80504	Longmont	CO	Zone 1 (High)	35/100
8	80534	Johnstown	CO	Zone 1 (High)	35/100
9	80543	Milliken	CO	Zone 1 (High)	36/100
10	80538	Loveland	CO	Zone 1 (High)	38/100
11	80016	Aurora	CO	Zone 1 (High)	39/100
12	80108	Castle Rock	CO	Zone 1 (High)	41/100
13	80134	Parker	CO	Zone 1 (High)	41/100
14	80603	Brighton	CO	Zone 1 (High)	41/100
15	80542	Mead	CO	Zone 1 (High)	42/100
16	80621	Fort Lupton	CO	Zone 1 (High)	42/100
17	80138	Parker	CO	Zone 1 (High)	44/100
18	80911	Colorado Springs	CO	Zone 1 (High)	44/100
19	80221	Denver	CO	Zone 1 (High)	45/100
20	80513	Berthoud	CO	Zone 1 (High)	45/100
21	80602	Brighton	CO	Zone 1 (High)	45/100
22	80112	Englewood	CO	Zone 1 (High)	47/100
23	80229	Denver	CO	Zone 1 (High)	47/100
24	80233	Denver	CO	Zone 1 (High)	47/100
25	80241	Thornton	CO	Zone 1 (High)	47/100
26	80601	Brighton	CO	Zone 1 (High)	47/100
27	80640	Henderson	CO	Zone 1 (High)	47/100
28	80925	Colorado Springs	CO	Zone 1 (High)	47/100
29	80111	Englewood	CO	Zone 1 (High)	48/100
30	80124	Lone Tree	CO	Zone 1 (High)	48/100
31	80928	Colorado Springs	CO	Zone 1 (High)	48/100
32	80951	Colorado Springs	CO	Zone 1 (High)	48/100
33	80015	Aurora	CO	Zone 1 (High)	49/100
34	80503	Longmont	CO	Zone 1 (High)	49/100
35	80615	Eaton	CO	Zone 1 (High)	49/100
36	80645	La Salle	CO	Zone 1 (High)	49/100
37	80915	Colorado Springs	CO	Zone 1 (High)	49/100
38	80922	Colorado Springs	CO	Zone 1 (High)	49/100
39	80118	Larkspur	CO	Zone 1 (High)	50/100
40	80301	Boulder	CO	Zone 1 (High)	50/100
41	80401	Golden	CO	Zone 1 (High)	50/100
42	80439	Evergreen	CO	Zone 1 (High)	50/100
43	80465	Morrison	CO	Zone 1 (High)	50/100
44	80516	Erie	CO	Zone 1 (High)	50/100
45	80517	Estes Park	CO	Zone 1 (High)	50/100
46	80524	Fort Collins	CO	Zone 1 (High)	50/100
47	80631	Greeley	CO	Zone 1 (High)	50/100
48	80831	Peyton	CO	Zone 1 (High)	50/100
49	80903	Colorado Springs	CO	Zone 1 (High)	50/100
50	80906	Colorado Springs	CO	Zone 1 (High)	50/100
51	80908	Colorado Springs	CO	Zone 1 (High)	50/100
52	80910	Colorado Springs	CO	Zone 1 (High)	50/100
53	80926	Colorado Springs	CO	Zone 1 (High)	50/100
54	80939	Colorado Springs	CO	Zone 1 (High)	50/100
55	81004	Pueblo	CO	Zone 1 (High)	50/100
56	81230	Gunnison	CO	Zone 1 (High)	50/100
57	80026	Lafayette	CO	Zone 1 (High)	51/100
58	80132	Monument	CO	Zone 1 (High)	52/100
59	80612	Carr	CO	Zone 1 (High)	52/100
60	80127	Littleton	CO	Zone 1 (High)	53/100
61	80234	Denver	CO	Zone 1 (High)	53/100
62	80634	Greeley	CO	Zone 1 (High)	53/100
63	81001	Pueblo	CO	Zone 1 (High)	53/100
64	81006	Pueblo	CO	Zone 1 (High)	53/100
65	80514	Dacono	CO	Zone 1 (High)	54/100
66	80921	Colorado Springs	CO	Zone 1 (High)	54/100
67	81226	Florence	CO	Zone 1 (High)	55/100
68	81419	Hotchkiss	CO	Zone 1 (High)	55/100
69	80520	Firestone	CO	Zone 1 (High)	56/100
70	80530	Frederick	CO	Zone 1 (High)	56/100
71	80610	Ault	CO	Zone 1 (High)	56/100
72	80620	Evans	CO	Zone 1 (High)	56/100
73	80650	Pierce	CO	Zone 1 (High)	56/100
74	80305	Boulder	CO	Zone 1 (High)	57/100
75	80535	Laporte	CO	Zone 1 (High)	57/100
76	80549	Wellington	CO	Zone 1 (High)	57/100
77	80642	Hudson	CO	Zone 1 (High)	57/100
78	80525	Fort Collins	CO	Zone 1 (High)	58/100
79	80624	Gill	CO	Zone 1 (High)	58/100
80	80644	Kersey	CO	Zone 1 (High)	58/100
81	81520	Clifton	CO	Zone 1 (High)	58/100
82	81526	Palisade	CO	Zone 1 (High)	58/100
83	81611	Aspen	CO	Zone 1 (High)	58/100
84	81623	Carbondale	CO	Zone 1 (High)	58/100
85	80521	Fort Collins	CO	Zone 1 (High)	59/100
86	80526	Fort Collins	CO	Zone 1 (High)	59/100
87	81212	Canon City	CO	Zone 1 (High)	59/100
88	80027	Louisville	CO	Zone 1 (High)	60/100
89	80303	Boulder	CO	Zone 1 (High)	60/100
90	80547	Timnath	CO	Zone 1 (High)	60/100
91	81003	Pueblo	CO	Zone 1 (High)	60/100
92	81007	Pueblo	CO	Zone 1 (High)	60/100
93	81008	Pueblo	CO	Zone 1 (High)	60/100
94	81615	Snowmass Village	CO	Zone 1 (High)	60/100
95	80116	Franktown	CO	Zone 1 (High)	61/100
96	81650	Rifle	CO	Zone 1 (High)	61/100
97	80512	Bellvue	CO	Zone 1 (High)	62/100
98	80528	Fort Collins	CO	Zone 1 (High)	62/100
99	80021	Broomfield	CO	Zone 1 (High)	63/100
100	80109	Castle Rock	CO	Zone 1 (High)	63/100

Methodology

Radon rankings are based on EPA county-level radon zone classifications. Zone 1 (highest risk) has predicted average indoor radon levels above 4 pCi/L — the EPA action level. Zone 2 is moderate (2-4 pCi/L) and Zone 3 is low (below 2 pCi/L). Within Zone 1, ZIP codes are sub-ranked by Home Safety Score to prioritize areas with compounding risk factors.

Data sources: EPA Safe Drinking Water Information System (SDWIS), FEMA National Flood Insurance Program, EPA radon zone maps, EIA electricity rates, and Consumer Confidence Reports. Last updated: 2026-08-14.

Frequently Asked Questions

What is EPA Radon Zone 1?

Zone 1 is the EPA highest-risk classification, meaning the county has predicted average indoor radon levels above 4 pCi/L — the level at which the EPA recommends mitigation. Radon causes about 21,000 lung cancer deaths per year in the U.S.

Should I test for radon?

The EPA recommends testing all homes regardless of radon zone. A DIY test kit costs $15-40. Professional testing costs $150-250. If levels exceed 4 pCi/L, mitigation systems ($800-2,500) can reduce radon by up to 99%.