Is radon high in Arapahoe County, Colorado?

Moderate. The model predicts a long-term basement average of 2.5 pCi/L in Arapahoe County (about 1.4× the US average of 1.8 and close to the Colorado average of 2.6). That is in the 2-4 pCi/L range where the EPA recommends considering mitigation. Ranked 55 of 64 Colorado counties.

Should I test for radon in Arapahoe County?

Yes, soon. With a predicted average of 2.5 pCi/L, many homes in Arapahoe County will test above the 4 pCi/L action level. Use a short-term kit first; if it reads 2 or higher, confirm with a long-term test or continuous monitor before deciding on mitigation.

What does EPA Radon Zone 1 mean for Arapahoe County?

Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and classifies whole counties. The newer model's predicted average of 2.5 pCi/L does not line up with Zone 1, which is common - the EPA itself says high-radon homes exist in every zone. Neither replaces a test of your own home.

How much does radon mitigation cost in Arapahoe County?

A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; Colorado quotes vary with foundation type (slab, crawlspace, basement), home size and local labor. Get two or three bids from certified mitigators listed by your state radon program or the EPA's find-a-professional page.

Radon levels in Arapahoe County, Colorado

ModerateEPA Zone 1

Predicted long-term basement average of 2.5 pCi/L (model estimate) across 17 ZIP codes - about 1.4× the US average of 1.8, close to the Colorado average of 2.6. Ranked #55 of 64 Colorado counties.

Test Arapahoe County, CO - the EPA says "consider fixing" in this range

The predicted basement average here is 2.5 pCi/L, in the 2-4 pCi/L band where the EPA recommends considering mitigation. Plenty of individual homes in a moderate area test above 4. Start with a short-term test; if it comes back at 2 or higher, follow up with a long-term test or a continuous monitor.

Get a short-term test kit →Or track it with a continuous monitor

Already tested at 4 pCi/L or higher? Find a certified mitigation professional (EPA). A mitigation system typically runs $800-$2,500 installed.

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Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.

2.5 ± 0.07

pCi/L predicted basement mean (model SD)

1.9 ± 0.06

pCi/L predicted upstairs (above-ground) mean

1.8-3.3

range of ZIP-level basement predictions in the county

What this means for Arapahoe

The typical Arapahoe County home is predicted in the 2-4 pCi/L band. The EPA's guidance for this range is to consider fixing, because there is no known safe level and roughly one home in several in a moderate area will test above 4.

Note that the EPA classifies Arapahoe County as Zone 1 while the newer model predicts 2.5 pCi/L. The zone map predates two decades of test data; where they disagree, we grade on the model but show both. County figures weight each ZIP by its 2010 Census population, so they describe where people live rather than empty land.

Comparable Colorado counties: Rio Grande County (2.5), Denver County (2.5), Elbert County (2.5), Jefferson County (2.5). The state's highest is Pueblo County at 4.2 pCi/L.

ZIP codes in Arapahoe County

Predicted basement and upstairs means by ZIP (model estimate). ZIPs whose land is mostly in this county.

ZIP	Basement	Upstairs	Grade
80013	2.0 ± 0.07	1.7	Moderate
80015	1.9 ± 0.06	1.8	Low
80012	2.8 ± 0.06	2.0	Moderate
80016	1.9 ± 0.06	1.8	Low
80010	2.6 ± 0.06	1.9	Moderate
80014	2.5 ± 0.06	1.8	Moderate
80017	2.4 ± 0.08	1.7	Moderate
80122	3.2 ± 0.07	2.4	Moderate
80112	2.5 ± 0.07	2.2	Moderate
80111	2.5 ± 0.07	2.1	Moderate
80120	3.1 ± 0.07	2.2	Moderate
80110	2.7 ± 0.07	2.0	Moderate
80113	2.8 ± 0.06	2.1	Moderate
80121	3.2 ± 0.07	2.4	Moderate
80018	1.8 ± 0.09	1.7	Low
80137	2.6 ± 0.06	2.0	Moderate
80105	3.3 ± 0.06	2.2	Moderate

If your test comes back at 4 pCi/L or higher

Mitigation is a routine job: a fan-driven pipe that vents soil gas from under the slab to above the roofline, typically $800-$2,500 installed (typical range; local quotes vary). Use certified professionals: EPA find-a-professional. Read the full mitigation guide.

Arapahoe County radon questions

Is radon high in Arapahoe County, Colorado?: Moderate. The model predicts a long-term basement average of 2.5 pCi/L in Arapahoe County (about 1.4× the US average of 1.8 and close to the Colorado average of 2.6). That is in the 2-4 pCi/L range where the EPA recommends considering mitigation. Ranked 55 of 64 Colorado counties.
Should I test for radon in Arapahoe County?: Yes, soon. With a predicted average of 2.5 pCi/L, many homes in Arapahoe County will test above the 4 pCi/L action level. Use a short-term kit first; if it reads 2 or higher, confirm with a long-term test or continuous monitor before deciding on mitigation.
What does EPA Radon Zone 1 mean for Arapahoe County?: Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and classifies whole counties. The newer model's predicted average of 2.5 pCi/L does not line up with Zone 1, which is common - the EPA itself says high-radon homes exist in every zone. Neither replaces a test of your own home.
How much does radon mitigation cost in Arapahoe County?: A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; Colorado quotes vary with foundation type (slab, crawlspace, basement), home size and local labor. Get two or three bids from certified mitigators listed by your state radon program or the EPA's find-a-professional page.

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