Radon Test Kit: 2026 Colorado Homeowner Buyer’s Guide
A radon test kit is the homeowner’s primary tool for finding out whether the radioactive gas seeping up from the soil under a home has reached levels that warrant action. EPA estimates radon causes roughly 21,000 lung cancer deaths in the United States each year, making it the second-leading cause of lung cancer after smoking. Colorado is one of the highest-risk states in the country — most Front Range counties sit in EPA Zone 1, the agency’s highest-risk classification. This guide walks through every kit type, every step of correct use, and the price and lab-certification landscape Front Range homeowners face in 2026. Health-adjacent guidance summarizes EPA, CDC, and CDPHE sources — consult a physician for respiratory symptoms, which radon does not cause acutely.
What a radon test kit actually measures
A radon test kit measures the concentration of radon-222 gas in indoor air over a specified sampling period. The result is reported in picocuries per liter (pCi/L) in the United States or becquerels per cubic meter (Bq/m³) internationally. EPA’s action level — the concentration at which mitigation is recommended — is 4.0 pCi/L. EPA also notes that concentrations between 2.0 and 4.0 pCi/L warrant consideration of mitigation because there is no known safe level of radon exposure; the action level is a practical balance, not a safety threshold.
The kit does not measure radon-daughter exposure, lung dose, or any direct health endpoint. It measures the gas in the air. From the measurement, the risk inference is based on EPA and BEIR VI dose-response models, which is why testing matters: knowing the indoor concentration is the only path to understanding the home’s radon exposure profile.
How short-term radon test kits work
Short-term tests run from 2 to 90 days, with most homeowner kits in the 2–7 day range. Three technologies dominate the consumer market:
Activated charcoal canister
The most common consumer kit. An open canister filled with activated charcoal sits in the test location for 2–7 days. Charcoal adsorbs radon and radon daughters from the surrounding air. At the end of the test period, the homeowner seals the canister and ships it to an EPA-recognized or state-certified laboratory. The lab measures gamma emissions from the trapped radon daughters using a sodium-iodide detector and calculates the average pCi/L during the exposure window.
Cost: typically $15–30 for the kit including return shipping and lab analysis. Lab turnaround 3–7 business days after lab receipt. Best for first-pass screening and for closing-window real-estate transactions.
Electret ion chamber (EIC)
A small chamber with a charged Teflon disc (the electret) measures radon by the rate at which radon alpha emissions discharge the electret over the exposure period. EIC results are read by a calibrated reader, not by mailing to a lab in the traditional sense. EIC is the technology many professional inspectors use because it produces fast, reusable, and accurate results without lab turnaround. Consumer EIC kits exist but are less common.
Alpha track detector (short-term)
A small plastic film records alpha-particle impact tracks during the exposure period. The film is etched in the lab, and the track density is counted under microscope to calculate the average concentration. Short-term alpha-track tests run 2–4 days. Less common in the consumer market than charcoal canisters but accepted by EPA.
Continuous radon monitors (CRMs) are the professional-grade short-term tool — electronic devices that log hourly concentrations and produce a chart of fluctuations during the test period. Front Range inspectors typically use CRMs for real-estate closing testing because the device’s hourly chart provides evidence the home was not opened up during testing.
How long-term radon test kits work
Long-term tests run 90 days to 1 year, capturing seasonal variation that short-term tests miss.
Alpha track detector (long-term)
The dominant long-term consumer technology. Same alpha-particle film as the short-term version, but exposed for 90+ days. Long-term alpha track gives the most representative annual-average concentration. Cost typically $25–45 including lab analysis.
Long-term electret ion chamber
Same EIC technology in a long-term configuration, less common in consumer markets.
EPA recommendation: if a short-term test produces a result of 4.0 pCi/L or higher, follow up with either a second short-term test or a long-term test to confirm. If the short-term result is 8.0 pCi/L or higher, EPA recommends immediate mitigation without a second test.
EPA-recognized and state-certified labs
The kit’s quality is only as good as the lab analyzing it. Two recognition programs apply:
National Radon Proficiency Program (NRPP)
A voluntary national certification program operated by AARST (American Association of Radon Scientists and Technologists). NRPP-certified labs and devices meet measurement-quality requirements.
National Radon Safety Board (NRSB)
A second national certification program with parallel requirements. Both NRPP and NRSB certifications are recognized by EPA and most state programs.
State-certified labs
Some states maintain their own lab certification programs. Colorado does not run a separate state lab certification — Colorado relies on the federal EPA recognition and NRPP/NRSB national certifications. CDPHE does run a contractor certification program for radon mitigation, separate from lab certification.
When buying a kit, look for either NRPP-Listed Device or NRSB-Listed Device language on the product. The lab name and certification should be visible on the kit’s documentation.
Front Range Colorado context and CDPHE subsidies
Colorado has one of the highest indoor-radon risk profiles in the United States. The combination of uranium-bearing geology (granite and shale in the foothills and Front Range), winter heating that creates strong stack-effect draws of soil gas into homes, and home construction styles (basements, slab-on-grade with utility penetrations) produces statewide elevated radon levels. CDPHE reports that approximately half of Colorado homes test above the 4.0 pCi/L EPA action level.
The CDPHE Radon Program offers free or reduced-cost short-term test kits to Colorado residents through county public-health departments. Availability varies by county and program funding. Front Range residents in Denver, Boulder, Larimer, Weld, El Paso, Jefferson, Adams, and Arapahoe counties commonly find subsidized or free kits through their county health department. The program is renewed annually; current availability is verified through CDPHE’s radon webpage or the county health department.
How to use a radon test kit correctly
EPA’s measurement protocol for residential short-term testing is published in detailed form, but the homeowner essentials are:
Lowest livable level
Place the kit on the lowest level of the home that is or could be used for living, sleeping, or extended-time activities (more than four hours per week). For most Front Range homes with a finished basement, this is the basement. For slab-on-grade homes, it is the lowest occupied floor.
20 inches off the floor
Position the kit at least 20 inches above the floor — typically on a desk, shelf, or table. This approximates the breathing zone of a seated person.
At least 4 feet from windows and exterior doors
Air movement from windows and exterior doors influences local concentration. Place the kit in the interior of the room, away from drafts.
At least 3 feet from HVAC vents
Forced-air supply vents move large volumes of air past the kit and can bias the reading.
48-hour-closed-house protocol for short-term tests
Begin the closed-house condition 12 hours before starting the test and maintain it throughout the test period. Keep doors and windows closed except for normal entry and exit. Do not run whole-house fans, attic fans, or window air conditioners. HVAC heating and cooling may run normally. This protocol prevents air-exchange dilution from biasing the result downward.
Document and ship promptly
Record start and stop times exactly. Ship to the lab promptly after closing the canister — the radon-daughter half-life (3.82 days for radon-222) means delayed shipping introduces decay correction that the lab software handles, but excessive delay reduces measurement accuracy.
What the result means
Result interpretation per EPA:
- Below 2.0 pCi/L — generally considered low. Re-test every 2–5 years; no immediate action required.
- 2.0–3.9 pCi/L — EPA “consider mitigation.” Re-test to confirm; mitigation may be appropriate especially in homes with young children or smokers.
- 4.0–7.9 pCi/L — EPA action level. Re-test with a different method (short-term confirmatory or long-term) to confirm, then mitigate.
- 8.0 pCi/L or higher — EPA recommends immediate mitigation without further confirmatory testing.
Mitigation system design and pricing for Front Range homes is covered in the radon reduction system guide. Typical mitigation cost runs $1,000–2,500 for a single-family Front Range home.
When short-term vs long-term testing makes sense
Short-term (2–7 days) — best for
Real-estate closing testing where the closing window is limited; initial screening of a new home; confirmatory testing after an unusually high or low result; post-mitigation verification testing.
Long-term (90+ days) — best for
Establishing the actual annual-average exposure; homes where seasonal variation may produce misleading short-term results; homes where occupants want the most accurate baseline before deciding on mitigation; ongoing monitoring after mitigation installation.
Limitations of radon test kits
Tests reflect the conditions during measurement. A 2-day test during a closed-house winter week is not the same as a 7-day summer test with windows occasionally open. Long-term tests average seasonal variation, but short-term tests can over- or under-estimate annual exposure depending on conditions. The 48-hour-closed-house protocol mitigates this for short-term tests but does not eliminate it.
Tests do not measure radon entry pathways. A 6.0 pCi/L result tells the homeowner that mitigation is warranted but does not say where the radon enters. Mitigation contractors typically perform a diagnostic assessment — sub-slab pressure testing, foundation-crack inventory, sump-pump assessment — to design the right mitigation system. The broader radon-in-Colorado context lives on the Colorado radon testing pillar.
Cost summary
- Charcoal canister short-term kit: $15–30 including lab analysis
- Long-term alpha track kit: $25–45 including lab analysis
- Professional CRM short-term test (inspector): $125–200 with documented chart
- CDPHE subsidized test kit (Colorado residents, varies by county): $0–10
How to choose between competing kit brands
The consumer radon test kit market includes several major brands — Air Chek, RadonZone, Pro-Lab, Health Metric, and others — alongside smaller specialty lab providers. The single most important selection criterion is not the brand on the box but the lab certification behind the analysis. Look for NRPP-Listed Device or NRSB-Listed Device language on the product packaging or the lab’s website. Both certifications attest that the device and the analyzing lab meet measurement-quality requirements that EPA recognizes.
Secondary considerations include the lab’s customer-service responsiveness (some labs send the result electronically the day the sample arrives; others take 7–10 business days), the kit’s packaging quality (humidity-sealed canister versus loose-fitting canister), and the included documentation (some kits provide a written interpretation; others provide just the number). Price varies less than these quality factors; a $25 kit from an NRPP-listed lab is generally preferable to a $15 kit from an unlisted lab.
What to do when the result arrives
The kit’s lab report typically arrives by email within 3–7 business days of lab receipt. Read the result carefully: the number reported is the average pCi/L during the exposure period, and the report should also include the start and stop times you provided, the lab’s certification number, and any uncertainty range associated with the measurement.
For results below 2.0 pCi/L, file the report and schedule a re-test in 2–5 years. For results between 2.0 and 3.9 pCi/L, consider a follow-up test (preferably long-term) and discuss mitigation if young children or smokers live in the home. For results at 4.0 pCi/L or higher, run a confirmatory test using a different method (long-term, or a second short-term with a different kit type), then contract with a CDPHE-recognized mitigation contractor. For results at 8.0 pCi/L or higher, EPA recommends immediate mitigation without a second confirmatory test.
The mitigation contractor’s diagnostic assessment and system design process is covered in the radon mitigation guide. Most Front Range homes can be mitigated for $1,100–2,500 with one workday of installation.
Real-estate transaction testing: special considerations
Radon testing during a real-estate transaction follows a specific protocol set by EPA and adopted by most state programs. The test is typically a 48-hour short-term measurement using a continuous radon monitor (CRM) operated by a CDPHE-recognized measurement professional, not a homeowner-conducted kit. The CRM produces an hour-by-hour chart that documents both the average concentration and any unusual deviations during the test period — important for transaction integrity because it shows the home was not opened up or HVAC-manipulated during testing.
Transaction-window testing typically runs $125–200 in the Front Range. Many home-inspection firms include radon testing as an add-on to the standard pre-purchase inspection, often at a discount versus standalone radon-only visits. Buyers electing radon testing during their inspection contingency should request a written report with the CRM chart, not just a single average number.
When to call a professional
For real-estate closing testing, hire a CDPHE-certified radon measurement professional using a CRM with documented chart. For initial homeowner screening, a $15–30 charcoal canister kit from an NRPP- or NRSB-listed lab is sufficient. For confirmatory testing after an elevated result, use a different method (long-term, or a second short-term with a different kit) before scheduling mitigation. For mitigation, hire a CDPHE-certified radon mitigation contractor.
References
- Buying a radon test kit — U.S. Environmental Protection Agency
- Colorado radon program — Colorado Department of Public Health and Environment
- Radon overview — American Lung Association
- Radon in the home — Centers for Disease Control and Prevention
Front Range homeowners with elevated kit results can reach a vetted local CDPHE-certified mitigation contractor through the contact page.
Radon test kits we recommend
Short-term charcoal kits are the cheapest way to get a first reading; mail the canister to the lab and results come back in days.
| Product | Why | Buy |
|---|---|---|
 AirChek Charcoal Radon Test Kit | Lab fee usually included; EPA short-term protocol. | Amazon — $21.95 |
 First Alert RD1 Radon Test Kit | Widely stocked; 48-hour charcoal test. | Amazon — $17.95 |
| Health Metric Radon Test Kit | Two-pack option for closed-house testing. | Amazon — $17.95 |