Test Radon in Home: What Homeowners Need to Know
Testing for radon in a home is a homeowner-led action. The steps are simple, the kit costs under $50, and the result tells you whether the home needs mitigation. This guide takes the homeowner action perspective: how to buy a kit, what to expect during the test, how to interpret the result, and what action to take based on the number that comes back. This guide summarizes EPA Indoor Air Quality and Colorado Department of Public Health and Environment guidance current as of 2026 and is not a substitute for a NRPP-certified professional when transaction documentation or mitigation is needed.
Part of our Radon Levels guide — start there for the full picture →
Test radon in home: where to start
Buy a short-term test kit from a hardware store, online retailer, or state radon program. Colorado’s CDPHE offers low-cost test kits through its radon program; the kit is typically $15 to $20 including lab analysis and shipping. Hardware-store kits (Home Depot, Lowes, Ace) typically run $20 to $35. Online options (FirstAlert, Pro-Lab, Air Chek) are similar. The kit you buy should have an EPA radon measurement listing or AARST-PROFICIENCY recognition; both marks indicate the kit and its analyzing lab meet quality standards.
Three short-term kit types to choose between: charcoal canister (most common, $15-25), electret ion chamber ($35-75 prosumer), or short-term alpha-track ($25-45). Charcoal canister is the right pick for a first test. For longer-term follow-up after an elevated short-term result, a 90-day alpha-track ($25-45) is the right pick. The Front Range radon testing guide covers Colorado-specific kit sources.
What to expect during the test
Once the kit is in the home, set up takes five minutes. Place the kit on a shelf or piece of furniture 20 inches to 6 feet above the floor at the lowest occupied level of the home (usually the basement). Pick a location away from exterior walls, windows, HVAC vents, kitchens, and bathrooms. Note the start time on the included information card. Peel back the seal that exposes the absorbent material. Walk away.
The test runs unattended for the duration specified by the kit, typically 48 hours for charcoal canisters. During this time you live in the home normally. Keep windows and exterior doors closed (closed-house conditions). HVAC operates normally. You can come and go through the front door; that brief opening does not invalidate the test. Do not run whole-house fans, attic fans, or air purifiers that affect whole-home air exchange.
Ending the test and shipping
At the end of the specified duration, reseal the kit. Charcoal canisters typically have a foil cover or replacement cap that gets taped over the opening. Note the end time on the card. Place the kit and the completed card in the supplied envelope and mail it the same day. Same-day shipping matters because charcoal canisters continue to absorb or desorb radon during transit, and the lab calculates the result assuming a known interval between exposure end and lab receipt.
Mail by first-class or expedited delivery. For a Colorado homeowner, most kit labs are in the Midwest or East Coast, so the canister arrives at the lab in two to three business days. Lab analysis takes another five to seven business days. Results typically arrive via email within 10 business days of mailing.
What the result will look like
The lab result includes the radon concentration in pCi/L (picocuries per liter), the start and end dates of the exposure, the duration, the lab’s QC notes if any, and a disposition statement. EPA’s action level is 4.0 pCi/L. Results at or above 4.0 pCi/L: mitigation recommended. Results between 2.0 and 4.0 pCi/L: mitigation worth considering, especially if the test was at the lowest occupied level and that level is regularly used. Results below 2.0 pCi/L: no mitigation needed; re-test every two to five years.
Colorado homeowners should be prepared for elevated results. CDPHE survey data shows approximately half of Colorado homes test above 4.0 pCi/L. A result of 5.0 to 10.0 pCi/L is common. Results of 20 pCi/L or higher are not unusual in some neighborhoods. The number is what it is; mitigation is straightforward and the cost is bounded.
Acting on a result at or above 4.0 pCi/L
The recommended next step after a single elevated short-term test is a confirmatory measurement. Two options: a second short-term test at the same location, or a 90-day alpha-track in the same location. EPA Protocol allows averaging two short-term tests if both run under closed-house conditions; if either is at or above 4.0 pCi/L, mitigation is recommended.
If both short-term tests confirm at or above 4.0 pCi/L, plan for mitigation. Mitigation is typically a sub-slab depressurization system (a fan pulling air from under the basement slab and venting it above the roofline). Cost: $1,200 to $2,500 in most Front Range markets for a typical home, sometimes higher for complex foundations or multiple slabs. Mitigation systems reliably reduce radon to below 2.0 pCi/L when designed and installed correctly.
Acting on a result between 2.0 and 4.0 pCi/L
Results in the 2.0 to 4.0 pCi/L range are the borderline zone. EPA recommends consideration of mitigation here, especially for homes where the lower level is regularly occupied as sleeping or living space. The cost-benefit math: a $1,500 mitigation installation eliminates an exposure of perhaps 3.0 pCi/L over the decades you live in the home. Cumulative dose reduction is meaningful, and mitigation systems have low operating cost (about $50 to $100 per year in electricity).
An alternative is a long-term alpha-track for 90 days or longer to confirm the annual-average concentration. Short-term results in this range can be biased by weather or unusual conditions during the test window. A 90-day average gives a more representative number. If the long-term average is below 2.0 pCi/L, no action. If it stays in the 2.0 to 4.0 range, mitigation becomes the recommended action. The how to do a radon test step-by-step covers test procedure depth.
Acting on a result below 2.0 pCi/L
A result below 2.0 pCi/L is a clean result. No mitigation needed. Re-test every two to five years. Re-test sooner if the home undergoes significant changes that affect pressure dynamics or soil-gas entry: new windows, new HVAC system, foundation repair, addition of a wood stove, completion of a finished basement project, or a major remodel.
Re-testing is cheap insurance. A $20 charcoal canister every two years is a $10-per-year cost to maintain confidence in the result over the years you own the home. Long-term alpha-track measurement is a good supplemental option for homeowners who want a multi-year track record.
Special cases: rentals, condos, new construction
Renters who want to test the unit can do so with the landlord’s permission. Most landlords allow testing because elevated results trigger mitigation that improves the property. Some states (Illinois, others) have rental radon disclosure rules; Colorado does not require landlord disclosure of radon test results but does encourage testing.
Condominium owners test their own unit. A unit on a lower floor with shared foundation contact behaves like a single-family basement; an upper-floor unit may test lower because of vertical distance from the soil source. Each owner-occupied unit makes its own mitigation decision.
New construction often includes passive radon-resistant features per the International Residential Code: a sub-slab gas-permeable layer, a vapor retarder, a vertical riser pipe, and electrical provision for a future fan. Test the new home after moving in. If results are at or above 4.0 pCi/L, activate the riser by adding a fan; this typically converts the passive system to an active system at a cost of $400 to $800.
When to hire a professional instead of self-testing
DIY testing is appropriate for owner-occupied homes with no transaction pending, post-mitigation verification, and periodic re-testing. Professional testing is appropriate for real-estate transactions (Protocol B with CRM and chain-of-custody is the standard), post-mitigation testing where the mitigation contractor’s warranty requires professional verification, and any situation where the result needs to be defensible to a third party.
Professional radon tests run $150 to $250 for a Protocol B CRM measurement. A NRPP-certified or state-licensed radon measurement professional performs the test. The deliverable is a report with hourly readings, the average pCi/L, closed-house condition verification, and a recommended action. The how to test for radon in your home full process guide covers when to escalate.
Annual or biennial check-ups
The radon test is one of the cheapest home maintenance items in any homeowner’s calendar. An annual or biennial $20 charcoal canister test maintains awareness of any changes in indoor radon over time. Pressure dynamics change with weather, HVAC equipment ages, foundation cracks develop, soil conditions shift. A single negative test ten years ago does not guarantee a negative test today.
For homes with installed mitigation systems, post-mitigation verification testing every two years is best practice. The mitigation fan can fail (usually predictably, after seven to ten years of operation), and a failed fan returns radon levels to pre-mitigation values. A simple charcoal canister test confirms the system is still working.
References
- EPA Citizen’s Guide to Radon — U.S. Environmental Protection Agency
- Colorado radon program and low-cost kits — Colorado Department of Public Health and Environment
- CDC radon and health — Centers for Disease Control and Prevention
- EPA radon-resistant construction — U.S. Environmental Protection Agency
Frequently asked questions
How much does it cost to test radon in home?
DIY short-term kits run $15 to $35 including lab analysis. Long-term alpha-track kits run $25 to $55. Professional Protocol B testing runs $150 to $250. Colorado's state radon program offers low-cost kits at $15 to $20.
How long does the whole process take?
The test runs 48 hours to 7 days. Mailing to the lab adds two to three days. Lab analysis takes five to seven business days. Total time from kit purchase to result is typically two weeks.
What if I test high in winter but low in summer?
Winter readings are usually higher because closed-house conditions are easier to maintain and stack effect is stronger. The annual-average exposure is what matters for health risk. A 90-day or 365-day alpha-track captures the annual average.
Do I need to re-test after mitigation?
Yes. Re-test 24 to 48 hours after the mitigation fan starts running under closed-house conditions. The target is a basement reading below 4.0 pCi/L and ideally below 2.0 pCi/L. Re-test every two years thereafter to verify the system continues to work.
Front Range homeowners ready to act on an elevated result or wanting a professional confirmatory test can reach out through our contact page.
Test your home for radon
Radon is invisible and odorless, so a test is the only way to know your level. A short-term kit gives a first reading in days; a digital monitor tracks it over time.
| 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 — $16.98 |
 Airthings Corentium Home | Digital monitor with a long-term average. | Amazon — $147.14 |