Colorado · Costilla County
Radon Levels in Costilla County, Colorado
In Costilla County, Colorado, 61.9% of pre-mitigation home radon tests came back at or above the EPA action level of 4 pCi/L — based on 21 tests collected by the Colorado Department of Public Health and Environment between 2005 and 2024. The county’s median pre-mitigation reading was 5.6 pCi/L, with a maximum recorded result of 21 pCi/L.
EPA recommends mitigation when long-term indoor radon measures at or above 4 pCi/L. Counties with elevated medians and large test counts — like Costilla — typically warrant testing during real-estate transactions and seasonal retesting in occupied homes.
Costilla County by the numbers
Source: Colorado Department of Public Health and Environment. Pre-mitigation indoor radon tests, 2005–2024.
- Tests above 4 pCi/L
- 61.9%
- Total tests recorded
- 21
- Median result
- 5.6 pCi/L
- Maximum recorded
- 21 pCi/L
EPA action level
CDPHE 2005–2024
pre-mitigation
outlier high
How Costilla compares to Colorado as a whole
Both bars show the percentage of pre-mitigation tests that came back at or above the EPA action level of 4 pCi/L.
CDPHE 2005–2024
Service note
We don’t service Costilla County directly.
Colorado Radon Check operates along the Front Range. For radon mitigation in Costilla County, we recommend finding a NRPP-certified mitigator near you — that credential is your best signal of a competent, accountable contractor.
Find an NRPP-certified proFilter by “Certified Mitigation Specialist” to see radon mitigation companies in Costilla County.
NRPP (the National Radon Proficiency Program) certifies measurement and mitigation professionals nationally. Colorado also issues state licenses for radon mitigators — ask your pro for both.
Free download
But the free Colorado Radon Risk Map still applies.
All 64 counties on one page — built from CDPHE’s 214,362 pre-mitigation tests. See where Costilla County ranks and what your neighbors are seeing.
Costilla County radon questions
- What level of radon is dangerous?
- The EPA recommends mitigation at 4 pCi/L or higher. Between 2 and 4 pCi/L, you should consider mitigation — long-term exposure at this range still carries lung-cancer risk. Below 2 pCi/L, the EPA suggests retesting every two years.
- How much does radon mitigation cost in Colorado?
- A standard sub-slab depressurization system in Colorado typically runs $1,200–$2,500, with $1,500 the most common all-in price. That single system reduces indoor radon by 95% or more in the majority of homes. Crawlspace installs cost more ($2,000–$5,000) because the membrane and tie-ins are more involved.
- Why are radon levels elevated in Costilla County?
- Geology drives most of it. Granitic bedrock and uranium-bearing soils — common across Colorado — release radon as they decay, and Front Range building style (basements, tight envelopes, forced-air systems) concentrates that gas indoors. Higher-elevation counties also tend to have lower atmospheric pressure, which can pull radon up through the foundation more aggressively.