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Radon Mitigation in Denver

Updated October 2026 · 10 public sources cited

Denver's health department says a radon reduction system should be installed when a home tests above 4.0 pCi/L. Here's how it works and how to make sure the installer is legal in Colorado.

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Why Denver homes test high

The EPA ranks Denver as Zone 1, which means the average house is likely to exceed the EPA action level of 4.0 pCi/L.1 Statewide, CDPHE says about half of Colorado homes are above that level and radon causes roughly 500 lung cancer deaths a year in Colorado.23 Radon comes from the breakdown of uranium in soil and enters through cracks, holes and pipes in the foundation. Denver's health department notes it can also come in through well water.1

Colorado requires a state license

Under Colorado law, an individual doing radon mitigation or measurement in the state must hold a license from the Division of Professions and Occupations. That has been required since July 1, 2022.45 Only licensed individuals may call themselves a "radon mitigation professional."4 DORA says Colorado adopted standards from the American Association of Radon Scientists and Technologists for licensed professionals, and consumers can report unlicensed work to the Office of Radon Professionals.5

National certification isn't the same as a Colorado license. Denver's health department lists national certification programs but says to verify that the contractor you pick is licensed by DORA.1 CDPHE keeps a licensed-professional lookup tool.6

How a Colorado system works

CDPHE says most systems use active soil depressurization. A radon fan and a barrier pull radon from the ground under the house and exhaust it above the roofline. The barrier is either the concrete foundation or 6-mil plastic sheeting in a crawl space.6

Basement or slab

The slab itself is the barrier, and a pipe through it draws soil gas out from below.6

Crawl space

6-mil poly sheeting goes over the soil as the barrier, and the system pulls from beneath it.6

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What CDPHE says to ask for

New construction and passive systems

CDPHE publishes guidance on radon-resistant construction for new homes and keeps a list of Colorado jurisdictions that require it.7 If your home already has a passive system built in during construction, CDPHE says adding a fan to activate it should cost about $500.6

Landlords: the 180-day rule

Colorado's 2023 radon law (SB23-206) gives tenants the right to know whether a rental has been tested. Before a lease is signed, the landlord must provide a written disclosure, any known test results and a copy of CDPHE's radon brochure.89 If a licensed professional finds 4 pCi/L or more and the landlord doesn't make a reasonable effort to mitigate within 180 days, the tenant may be able to void the lease. Since January 1, 2026, that remedy no longer applies to leases of one year or less.9

After it's installed

CDPHE recommends testing even when a system is in place. With a working system, retest in 2 years if you're under 2 pCi/L. If you're at 4 or higher, call a licensed mitigation pro to service it, and check with the original installer in case it's under warranty.6

Areas we serve

We match homeowners across the Denver area, including these communities and ZIP codes:

ZIP codes are 2020 Census ZIP Code Tabulation Areas, which closely approximate USPS ZIP codes. We list ZIPs that make up a substantial share of each community, so edge ZIPs that barely touch a town are left out, and some ZIPs span two towns.10 Not on the list? Send the form anyway, and we'll tell you if we can help.

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The home is

By tapping “Get my free referral,” I agree that Radon Help Network may send my request to one local radon mitigation company serving Denver, and that this one company may call and text me about my request at the mobile number I entered, including with an autodialer, prerecorded or artificial (AI-generated) voices, and automated texts. Consent is not a condition of any purchase; to get help without agreeing, use our contact form. Msg & data rates may apply; message frequency varies. Reply STOP to opt out. Privacy Policy · Terms

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Common questions

Does a radon mitigation contractor need a license in Colorado?

Yes. Since July 1, 2022, individuals doing radon mitigation or measurement in Colorado must be licensed by the Division of Professions and Occupations at DORA.

Is national NRPP or NRSB certification enough in Denver?

Denver's health department lists those national programs but tells residents to verify the contractor is licensed by DORA. The state license is what Colorado law requires.

How many bids should I get?

CDPHE recommends at least three bids, like any home repair, and asking for a guarantee below 4 pCi/L plus at least a five-year warranty on the fan and workmanship.

My home has a passive radon pipe. What does it cost to activate?

CDPHE says adding a fan to activate a passive system built in during construction should cost about $500.

Does a Denver landlord have to fix high radon?

Colorado law requires landlords to disclose radon information before a lease. If a licensed professional finds 4 pCi/L or more and the landlord doesn't make a reasonable effort to mitigate within 180 days, the tenant may be able to void the lease. Since 2026 that remedy doesn't apply to leases of one year or less.

Should I test again after mitigation?

Yes. CDPHE says to test even with a system installed. Under 2 pCi/L, retest in 2 years. At 4 or higher, have a licensed mitigation pro inspect and service the system.

More for Denver

Other cities

General information summarized from the public sources listed below. It isn't professional, medical or legal advice. A licensed professional who inspects your home can tell you what it needs.

Sources

  1. City and County of Denver, Department of Public Health & Environment, "Radon"
  2. CDPHE press release, "Half of Colorado homes have elevated radon levels" (Jan. 5, 2026)
  3. Colorado Department of Public Health and Environment (CDPHE), "Radon"
  4. Colorado Revised Statutes § 12-165-106
  5. Colorado Department of Regulatory Agencies, "Radon professional licensure now required in Colorado"
  6. CDPHE, "Radon FAQ"
  7. CDPHE, "Radon and real estate"
  8. Colorado Revised Statutes § 38-12-803 (radon disclosure to tenants)
  9. Colorado Division of Real Estate, "Broker Practice Advisory: SB23-206"
  10. U.S. Census Bureau, 2020 ZCTA-to-place and ZCTA-to-county-subdivision relationship files
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