Real Test Results From 600+ Local Tests
This map and chart are built from radon tests I've personally conducted across Southwest Colorado — not regional estimates or EPA zone data. Data spans January 2020 through April 2026. Each bubble represents a city and its surrounding area. Click any bubble for local test results, or scroll down for a city-by-city breakdown.
Interactive Map
Radon Levels Across the Region
By City
Frequency of High Radon Results by City
Percentage of homes tested that came back at or above the EPA action level of 4 pCi/L, compared to the U.S. national average of approximately 6.7% (roughly 1 in 15 homes). Each bar reflects results across that city and surrounding rural area. Confidence on the right indicates how many tests back up the result — High = 50+ tests, Moderate = 15–49, Limited = fewer than 15. Whether a specific home requires mitigation depends on that property's individual test result.
Understanding the Risk
Radon Is Common
in Southwest Colorado
Radon is an invisible, odorless gas produced by uranium naturally present in our regional geology. You can't smell it, see it, or taste it — and it's one of the most important things to test for when buying a home here.
Leading Cause of Lung Cancer
Radon is responsible for approximately 21,000 lung cancer deaths in the U.S. each year, according to the EPA. It's the number one cause among non-smokers. New research has also shown possible links to childhood leukemia.
Of Local Homes Test High
Based on over 650 radon tests performed in La Plata and Montezuma counties, roughly 1 in 5 homes in our area tests above the EPA's action level of 4 pCi/L. That number is well above the national average.
EPA's Highest-Risk Designation
Southwest Colorado sits in EPA Radon Zone 1 — the highest-risk classification in the country. Our uranium-rich geology, elevation, and tight home construction during cold months all contribute to elevated indoor concentrations.
Mitigation Is Effective and Manageable
If your home tests high, a mitigation system is typically installed in 1–3 days and significantly reduces indoor radon levels. It's a significant investment — and systems require retesting every two years and occasional maintenance over time. Testing before your objection deadline gives you leverage: sellers frequently cover mitigation costs when levels are shown to be elevated.
EPA Radon Guidance
What Your Test Result Means
The EPA measures radon in picocuries per liter of air (pCi/L). Their guidance is straightforward — and in Southwest Colorado's Zone 1, anything above 4 pCi/L warrants action.
About This Data
Where the Numbers Come From
Every data point on this map comes from a radon test I personally conducted as part of a professional home inspection — 623 unique addresses across La Plata and Montezuma counties, collected between January 2020 and April 2026. No estimates, no modeling, no EPA zone averages.
Real Field Data
Each location represents an actual continuous electronic radon test performed over a minimum 48-hour period using calibrated NRPP-standard monitors. Results are from my personal inspection records collected over years of work in the region.
Bubble Size = Test Count
Each bubble represents all tests performed in that city and surrounding area — urban and rural combined. Larger circles indicate higher data confidence. Smaller circles in less-tested areas should be interpreted with that context in mind.
Privacy Protected
Rural marker locations are approximate — shifted slightly from actual addresses to protect client privacy. City marker positions reflect the city center. Aggregate data patterns are accurate and reflect real measured levels.
Licensed by the State of Colorado
I hold a Colorado Radon Measurement Professional License (RME.0000058), making me one of a limited number of state-licensed radon testers in the region. Tests are performed using calibrated electronic continuous monitors and conducted in accordance with Colorado state standards.
If Your Home Tests High
How Radon Mitigation Works
Sub-slab depressurization (SSD) is the primary mitigation method for slab and basement foundations. Crawl space homes use sub-membrane depressurization (SMD). Both are recognized under AARST-ANSI SGM-SF standards and referenced by NRPP certification.
Initial Assessment
The mitigator reviews the radon test results and inspects the home's foundation, slab, and any existing penetrations. Formal diagnostic testing — such as sub-slab pressure field extension testing — is specified under AARST-ANSI SGM-SF standards but is not always performed in practice. More commonly, the mitigator uses visual inspection and experience to determine suction point placement.
Suction Point Installation
A hole is cored through the concrete slab and a suction pit is created in the crushed rock or soil below. Per AARST-ANSI SGM-SF standards, the location and depth are chosen to maximize pressure field extension beneath the slab.
Pipe and Fan Installation
PVC pipe runs from the suction point through or along the wall to the exterior. A continuously operating fan creates negative pressure below the slab, drawing radon out before it can enter the home. A good mitigator thinks carefully about routing — running pipe through closets, along interior walls, or into attic spaces where possible to keep the system as discreet as the home allows. The goal is a system that works well and doesn't look like an afterthought.
Discharge Above Roofline
Per NRPP and EPA requirements, the exhaust pipe must terminate above the roofline and away from windows and air intakes, so extracted radon disperses safely into the open air rather than re-entering the structure.
Post-Mitigation Testing & Ongoing Monitoring
A post-mitigation radon test is conducted after system installation — typically 24–48 hours after — to confirm the system is working. The EPA and NRPP recommend retesting every two years and after any major renovations. Systems should also be inspected periodically for fan function and pipe integrity.
Get Your Inspection —
Add Radon Testing While You're At It
Radon testing is easy to add to any home inspection. Given our region's geology, it's a test worth doing.