What to do with a result you already have

A radon test result is not a verdict about your health or your house. It is a number that official guidance asks you to compare against a fixed threshold, then act on a defined way. The U.S. EPA recommends taking action to fix your home when radon levels are above 4 picocuries per liter (pCi/L), and EPA Region 7 words the same benchmark as four pCi/L "or more." EPA also says that because there is no known safe level of radon exposure, people should consider fixing a home for levels between 2 and 4 pCi/L. Those two statements come from the same agency and belong together: act at four, and think seriously about the range below it.

Colorado adds context to why the threshold matters. CDPHE states that roughly half of Colorado homes exceed the EPA action level of 4.0 pCi/L, based on its January 2026 announcement. That is a statewide statistic, not a prediction for your address, and it is the reason state and federal agencies treat testing as routine rather than exceptional.

First, decide whether the test itself is finished

Before you plan remediation, confirm that the number is a valid measurement. CDPHE describes short-term tests as running from 48 to 120 hours, with the house closed for 12 hours before the device is activated and doors and windows kept shut for the duration. It also lists conditions that undermine a test: devices placed in crawl spaces, closets, kitchens, laundry rooms or bathrooms; near exterior doors, windows or walls; near vents, fans or direct sunlight; or run while a whole-house fan operates. If any of those applied, the honest next step is a new test rather than a mitigation decision.

For longer coverage, CDPHE describes long-term tests taking 91 days to a year under normal living conditions, using alpha-track detectors or electronic instruments. It notes that long-term results give a more representative picture over time. For official test-kit handling and placement details, see CDPHE's testing and mitigation page.

Where retesting fits

Retesting is not only for people worried about a first result. CDPHE recommends that homeowners who already have mitigation systems retest every two years to confirm the system is working. EPA guidance in its radon resource directory recommends testing every home at least every five years, or at least every two years to verify continued effectiveness of mitigation systems or other efforts. The Colorado figure is the more specific instruction for a home with a system; the EPA figure covers homes without one too.

Translate guidance into a working plan

The practical sequence officials describe is short: test, compare against the action level, fix if the level is at or above four pCi/L, and retest afterward. CDPHE calls mitigation systems the best way to reduce elevated radon and identifies sub-slab depressurization, or sub-membrane depressurization for a crawl space, as usually the most effective solution. It also cautions that caulking and sealing, while done as part of mitigation to hold conditioned air in, are not recommended as a stand-alone technique. EPA states that reduction systems can lower indoor levels by up to 99%, an upper bound rather than a promise for any particular house.

Cost context matters when planning, and it is worth stating as context rather than as a quote. CDPHE's testing and mitigation page notes that a mitigation system in Colorado usually costs about $1,000 to $2,000 unless difficult design problems arise. Treat that as a general range from a state source, check current information with CDPHE or a licensed professional, and do not assume it is what your house will cost.

A worked example, clearly hypothetical

Suppose a homeowner in a Denver-area house places a short-term kit in a finished basement office, closes exterior doors and windows for the full test, and receives a result of 5.1 pCi/L. On the supplied guidance, that level is above the 4 pCi/L action level EPA describes, so the next step is planning mitigation, not retesting until a lower number appears. She would hire a certified radon mitigation professional licensed through the Colorado Department of Regulatory Agencies, ask how the system will be verified after installation, and schedule a post-mitigation test. She would also note that her basement office is exactly the kind of space CDPHE flags, since people who spend significant time in basement offices or gyms are more exposed to radon that collects there.

Now suppose a different hypothetical result: 2.9 pCi/L. That is below the 4 pCi/L action level but inside the 2 to 4 pCi/L band where EPA says people should consider fixing. The plan changes from "arrange mitigation now" to "decide deliberately" — perhaps a long-term test for a more representative reading, and a conversation with a certified professional about what the level means for that house. Neither scenario is a health diagnosis; both are steps drawn from the published guidance.

Ask where the help is, and who is authorized

CDPHE states plainly that it provides information and advice only and cannot test a home, and that it does not accredit, certify, recommend or endorse listed individuals or companies. Contractors on its lists are certified by the National Radon Proficiency Program or the National Radon Safety Board and must be licensed by the Colorado Department of Regulatory Agencies. If a problem arises, CDPHE directs complaints about certification to NRPP or NRSB and licensing complaints to DORA. That structure is useful: a certification is not the same as a license, and checking both is a reasonable habit.

For homeowners who cannot afford a system, CDPHE describes a Low-Income Radon Mitigation Assistance program with an application process for qualifying homeowners and reported mitigating more than 200 homes through it in 2025. CDPHE's January 5, 2026 announcement also said free test kits were offered while supplies last. Eligibility and current availability should be confirmed directly with CDPHE rather than assumed.

Renters have separate footing. CDPHE notes that tenants may test their own units under Colorado law and that, as of August 7, 2023, landlords in Colorado must disclose radon information when a tenant signs a lease. This guide does not interpret legal disclosure duties; that is a question for CDPHE's materials or a qualified adviser.

If a home draws from a private well and the indoor air test found a radon problem, CDPHE advises testing the water as well, and says water-testing kits are available online and at most home improvement stores.

The next step, in one line

Write down your test result, the date, the device used and whether closed-building conditions held for the whole period; compare the number with the 4 pCi/L action level and the 2 to 4 pCi/L consideration band; decide between retesting, mitigation, or both based on that comparison; and confirm current program details, contractor credentials and cost expectations with CDPHE and a licensed professional before committing money or time. Our guide to starting a reliable test and our questions to ask a radon professional support that sequence.