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Radon in Westminster, Colorado

Westminster lies in 2 counties, in EPA Zone 1; 50% of it is in Adams County, where 36.6% of 1,191 reported tests (2023) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so the only way to know your home's level is to test it.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    36.6%

    2.3 pts below CO

    Adams
    36.6%
    Colorado
    38.9%

    Adams, 26th of 38 in CO, 2023

  • Median result

    2.3pCi/L

    Below action level

    Adams
    2.3 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of Adams's tests, 2023

  • Highest county

    41.8%

    Jefferson

    Jefferson
    41.8%
    Adams
    36.6%

    2 counties, 2 with 30+ tests, 2023

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    Adams; Jefferson Zone 1

  • Tests reported

    1,191

    In Adams

    Adams
    1,191
    Jefferson
    3,068

    Reported to CDC before any fix, 2023

Read a result for Westminster

Starts at Adams County's median, 2.3 pCi/L

2.3pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 2.3 pCi/L

Between 2 and 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Adams County's median reported result, 2023.

Interpret this readingWhat a fix costs

The data

Westminster, What is published

What is published for Westminster

Information:

Every figure for Westminster is a county's

Radon data is published by county, not by city, and Westminster reaches into 2 counties: Adams County and Jefferson County. Each has its own EPA zone and its own CDC test figures, set side by side below and each labelled with its county. Only a test tells you about one home.

Westminster covers 31.6 square miles of land: 50.0% of it lies in Adams County and 49.9% in Jefferson County. About 116,182 people live there, 3,678 to the square mile.

Westminster, Counties

Westminster's counties, side by side

Measured

Each county's own EPA zone and its own published CDC figures for 2023, the newest period any of them has. A county without a figure for that period is shown without one, never with a figure from another year.

  • Adams County
    EPA zone
    Zone 1: Highest predicted potential
    At or above 4 pCi/L
    36.6%
    Median result
    2.3 pCi/L
    Tests reported
    1,191 tests
    Annual years on file
    10
  • Jefferson County
    EPA zone
    Zone 1: Highest predicted potential
    At or above 4 pCi/L
    41.8%
    Median result
    3.2 pCi/L
    Tests reported
    3,068 tests
    Annual years on file
    10
The counties Westminster lies in, each with its own EPA zone and its own published CDC figures for 2023
CountyEPA zoneReported tests at or above 4 pCi/LMedian reported resultTests reportedAnnual years on file
Adams CountyZone 1: Highest predicted potential36.6%2.3 pCi/L1,191 tests10
Jefferson CountyZone 1: Highest predicted potential41.8%3.2 pCi/L3,068 tests10

Westminster spans 2 counties, each with its own EPA zone and its own CDC figure: Adams County (Zone 1, 36.6% of 1,191 tests) and Jefferson County (Zone 1, 41.8% of 3,068 tests).

Adams County ranks 26th of 38 Colorado counties with 30 or more tests for that period, 2.3 points below the 38.9% pooled across Colorado's counties, 3.2 points above the national pool of 33.4%. Of the city's other county, Jefferson County reported 41.8%.

Measured from the middle of Westminster, the nearest counties with a CDC figure for 2023 are Broomfield County (5 miles, 36.9% of 758 tests), Denver County (13 miles, 35.4% of 2,277 tests) and Boulder County (21 miles, 34.2% of 1,963 tests). Across the 8 nearest, the share at or above 4 pCi/L runs from 26.4% to 49.4%; the farthest of them, Larimer County, is 58 miles away at 49.4%.

The directory lists 1 business with an address in Westminster, 1 for mitigation. Colorado's other cities with a page of their own: Colorado Springs, Fort Collins, Grand Junction and Aurora.

Against Colorado and its other counties

Radon test figures for the counties Westminster lies in
CountyShare of WestminsterTestsAt or above 4 pCi/LMedianColorado, pooledRank in the stateEPA zone
Adams County50.0%1,19136.6%2.3 pCi/L38.9%26 of 38Zone 1
Jefferson County49.9%3,06841.8%3.2 pCi/L38.9%17 of 38Zone 1

Shares of tests people chose to run and report, by county (2023); the state's is its counties' counts added up, calculated by Radon411. Only a test measures a home.

The counties around Westminster

By distance from the middle of Westminster; counties with 30 or more tests.

Nearest counties to Westminster with 30 or more tests
CountyDistanceTestsAt or above 4 pCi/LMedian
Broomfield County5 mi75836.9%2.3 pCi/L
Denver County13 mi2,27735.4%2.8 pCi/L
Boulder County21 mi1,96334.2%2.5 pCi/L
Gilpin County25 mi12926.4%1.1 pCi/L
Clear Creek County34 mi5141.2%3.0 pCi/L
Douglas County39 mi1,63535.8%2.4 pCi/L
Arapahoe County42 mi1,99037.9%2.5 pCi/L
Larimer County58 mi1,90249.4%3.8 pCi/L

The median reported pre-mitigation result for 2023 was 2.3 pCi/L in Adams County and 3.2 pCi/L in Jefferson County.

Predicted: EPA Map of Radon Zones, by county. Measured: CDC tracking data, by county, 2023.

Westminster, Geology

The ground under Westminster

Predicted

USGS's geologic map puts all of Westminster's mapped land in one class: high radon potential. All of it lies in the area the map calls High Plains, to which USGS gives a radon index of 12, in the high band (12 to 17).

USGS's geologic areas under Westminster
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
High PlainsQuaternary deposits and Cretaceous marine shales that locally have a high radiometric signature.High12100%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Westminster beside its counties and Colorado

All of Westminster, like all of Adams County, is rated high. Westminster has more high-potential ground than Colorado as a whole: 100% of its land against 74.8%.

Share of land by USGS radon potential: Westminster, the counties it lies in and Colorado
AreaEPA zoneLow potentialModerate potentialHigh potential
WestminsterBy countyNoneNone100%
Adams CountyZone 1NoneNone100%
Jefferson CountyZone 1NoneNone100%
Colorado64 counties, pooled by land areaVariesNone25.2%74.8%

The map rates the ground, not the air in any home.

Westminster, Homes

Homes in Westminster

Of Westminster's 50,166 homes, 56% are detached houses, against 63% across Adams County; 29% are in buildings of five or more homes. Half of its homes were built before 1987, close to Adams County's 1990: 8% date from before 1960 and 24% from 2000 or later. 64% of occupied homes are lived in by their owner (Adams County: 69%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Westminster, Adams County, Colorado, 2019 to 2023
HomesWestminsterAdams CountyColorado
Housing units50,166191,7652,545,124
Detached houses56%63%62%
In buildings of 5 or more29%19%22%
Mobile homes1%6%4%
Built before 19608%13%16%
Built since 200024%36%31%
Middle year built198719901987
Owner-occupied64%69%66%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.

Local help

Westminster, Professionals

Radon professionals listed in Westminster

Businesses whose listed city is Westminster, from the state registries and listings in the Radon411 directory, with the same business and certification status the directory shows.

1 listing with Westminster as the city. See radon mitigation in Westminster, or all radon professionals in Colorado.

Westminster, Local resources

Local resources for Westminster

Who to ask in Colorado: its radon program, test kits and professionals.

The program's own words on licensing and disclosure are on the Colorado page.

What it means

Westminster, Questions

Questions about radon in Westminster

What radon zone is Westminster in?

Both counties Westminster reaches into (Adams County and Jefferson County) are in Zone 1, the map's highest class: a predicted county average above 4 pCi/L. EPA zones counties, not cities, so that is the zone for every part of Westminster.

What are radon levels in Westminster?

Around Westminster, 36.6% of 1,191 tests reported from Adams County for 2023 reached 4 pCi/L or more, so a high result is no surprise here. The median reported result was 2.3 pCi/L. Jefferson County reported 41.8% of 3,068 tests; the counties are kept apart.

Should I test my home in Westminster?

Yes. Adams County reported about 436 of its 1,191 tests at or above 4 pCi/L. That is below Colorado's pooled 38.9%, and still not a reason to skip it, and ranks Adams County 26th of the 38 Colorado counties with 30 or more tests. Which homes they were, no map can say. How to test a home.

What ground is Westminster built on, as far as radon goes?

USGS's geologic map puts all of Westminster on one named area, "High Plains", rated high for radon potential, radon index 12.

Is radon higher in the counties around Westminster?

It depends which way you go. 4 of the 8 nearest counties with a figure report a larger share than Adams County's 36.6% and 4 a smaller one: from Gilpin County (26.4%, 25 miles off) to Larimer County (49.4%, 58 miles off).

Who tests for or fixes radon in Westminster?

Westminster is the address of one business in Radon411's directory, listed for mitigation, none for testing. Each entry names the public list it came from. Radon professionals in Westminster.

The answers use the published figures of Adams County and Jefferson County, the counties Westminster lies in.

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