Radon Test Home: A 2026 Homeowner Process Walkthrough
A radon test in a home is a low-effort, high-information project. The whole sequence runs from “buy the kit” to “have the answer” in 7 to 10 days for a passive test, or 48 hours for a continuous monitor. This guide summarizes EPA and CDPHE guidance current as of 2026 and is not a substitute for professional measurement when transaction documentation is required. The process below assumes a homeowner doing a baseline screening test, not a real-estate transaction test — though the protocol overlaps significantly. Front Range residents have particular reason to test, because CDPHE estimates roughly 50 percent of Colorado homes register above EPA’s 4 pCi/L action level.
Step 1: Choose the test type
Three options cover almost every home situation.
Short-term passive kit (48 to 96 hours)
Charcoal canister or electret ion chamber. Cost $20 to $50 including lab analysis. Best for baseline screening and real-estate transactions when the window is tight. Vulnerable to short-term weather and ventilation anomalies. Available at most hardware stores and through state radon programs.
Long-term passive kit (90 days to 1 year)
Alpha-track detector. Cost $30 to $80 including lab analysis. Best for understanding seasonal patterns and confirming whether a screening result was a fluke. More representative of true annual exposure but requires patience.
Continuous radon monitor (CRM)
Consumer-grade units run $200 to $300. Professional units used for real-estate testing cost the homeowner $200 to $400 including the visit. CRMs log hourly readings, distinguish valid tests from interference, and produce immediate results. Best for ongoing monitoring and transactions requiring fast turnaround.
For a first-time home screening, a $25 charcoal canister deployed during heating season usually suffices. The companion DIY radon test guide compares specific kit brands.
Step 2: Identify the test location
Place the test on the lowest occupied level of the home. For homes with finished basements used regularly, that means the basement. For homes with unfinished basements used only for storage, the lowest occupied level is the first floor. The test goes in the room where the family actually lives — bedroom, family room, home office — not in a closet, mechanical room, or utility space.
Within the chosen room, the detector sits on a stable surface 20 to 70 inches above the floor (counter height works), at least 12 inches away from exterior walls, at least 3 feet from doors, windows, and any source of drafts, at least 4 inches away from other objects, and at least 7 feet away from heat sources and high-humidity sources like a bathroom door. The placement requirements are mostly common sense: avoid drafts, avoid heat, avoid stagnant pockets behind furniture. The radon test basement placement guide covers location selection for finished basements in detail.
Step 3: Establish closed-house conditions
Closed-house conditions mean windows and exterior doors stay closed for 12 hours before deployment and throughout the test, except for normal short-duration entry and exit. HVAC operates normally during the test — no special settings. Whole-house fans, attic fans, and continuous bath exhausts should be off during the test. Window air conditioners cycling is acceptable. Ceiling fans running is acceptable.
Closed-house conditions are easier to maintain in winter than in summer. A summer test on a 95-degree day with a homeowner who normally keeps windows open all day can be difficult to execute correctly. EPA recommends winter testing when possible for that reason. Front Range homeowners can typically maintain closed-house conditions any month from October through April without significant lifestyle disruption.
If a test runs through a brief weather event — a wind storm, a thunderstorm with rapidly changing barometric pressure — the result may be slightly skewed. Severe weather conditions warrant a retest under more stable atmospheric conditions.
Step 4: Deploy the kit
Open the kit. Most charcoal canisters arrive sealed inside a foil pouch. Open the pouch only when ready to deploy — exposure starts the moment the canister contacts room air. Note the start date and time on the kit’s chain-of-custody form. Place the canister at the selected test location with the open side facing up. Do not move the kit during the test. Do not place anything on top of it.
Electret ion chambers work similarly — note the start time and place the device with vents unobstructed. CRM deployment differs: the homeowner activates the device through its display, confirms the time clock, and walks away. CRMs typically include a 1-hour “stabilization period” during which the first hour of data is discarded.
Step 5: Wait for the test duration
48 hours is the minimum for charcoal canisters. 72 to 96 hours improves data quality. Don’t move, open, or touch the kit during the test. Encourage family members to maintain normal HVAC and occupancy patterns. Don’t run unusual ventilation (long hot showers with bath fan on, prolonged stovetop cooking with range hood, garage door open for extended periods).
Track any anomalies in the chain-of-custody form. A power outage that interrupted HVAC, a window left open by a guest, a contractor in the home for plumbing work — all are notable. The lab analyzing the result reads the chain-of-custody form and flags suspect deployments.
Step 6: Close out the test
At the end of the test period, immediately reseal the canister in its foil pouch (charcoal) or close the device per manufacturer instructions (electret, CRM). Note the end date and time. Complete the chain-of-custody form: home address, test location within the home, start and end times, any anomalies, contact information for results delivery.
Ship to the lab in the prepaid envelope within 24 hours of test close-out. Most kits include overnight shipping prepaid. Charcoal canisters lose accuracy if delivery to the lab takes more than 5 days from test end, because the half-life of radon decay products in the canister limits the measurement window.
Step 7: Read the result
Laboratory analysis takes 3 to 7 business days for passive tests. Results arrive by email, mail, or both. The report includes the home address, deployment dates, average radon concentration in pCi/L, the laboratory’s certification information, and basic interpretation guidance.
Three result categories matter.
Under 2 pCi/L: low. Retest every 2 years. EPA considers this acceptable.
2 to 4 pCi/L: borderline. EPA suggests considering mitigation. Retest in heating season if the current result was a summer test. Long-term alpha-track or CRM monitoring clarifies whether seasonal swings push readings above 4.
Above 4 pCi/L: elevated. EPA action level. Mitigation strongly recommended. Sub-slab depressurization on a Front Range single-family typically costs $1,200 to $2,500. The Colorado radon mitigation guide walks through what installation looks like.
Common deployment mistakes
Five mistakes account for most invalid test results.
Placement in the wrong room. A test in an unoccupied storage closet doesn’t represent breathing-space exposure. The test goes where the family lives.
Failure to maintain closed-house conditions. A homeowner who forgets and opens windows on day 2 of a 4-day test invalidates the result. Set a phone reminder if needed.
Drafty placement. A detector near an exterior wall, an HVAC vent, or a window will read low compared to representative breathing space.
Slow shipping to the lab. Charcoal canisters decay. Mail the kit the same day or next day the test ends.
Failure to log anomalies on chain-of-custody. The lab interprets results in context. A test during a foundation crack repair, a heating system replacement, or an unusually long vacation will read differently than a normal-conditions test. Note these on the form.
When to escalate from DIY to professional testing
Three situations warrant a certified radon measurement professional rather than DIY.
Real-estate transactions. EPA’s real-estate protocol specifies certified measurement professionals, chain-of-custody documentation, and CRM tests with interference logging. The buyer’s lender, the buyer’s agent, and the listing agent all rely on the professional’s documentation in negotiations.
Borderline results requiring tight measurement. A series of DIY results clustered around 3.5 to 4 pCi/L makes the mitigation decision hard. A professional CRM test resolves the question with hourly logs and tight calibration.
Post-mitigation verification. After spending $1,200 to $2,500 on a mitigation system, the verification test should be professional grade with proper documentation. EPA recommends professional post-mitigation testing for that reason.
The decision framework at radon testing services covers when professional testing pays off and when DIY suffices.
What to do with the result
Save the result in your home records. Future buyers, insurers, and renovation contractors will benefit from documentation. For elevated results, schedule mitigation consultations within 30 days. For borderline results, schedule a winter retest or a CRM deployment for longer-term data. For low results, mark a calendar reminder to retest in 2 years.
The radon testing pillar covers the Colorado-specific context for ongoing monitoring and CDPHE outreach resources that occasionally subsidize test kits for Front Range residents.
References
- EPA Citizen’s Guide to Radon — U.S. Environmental Protection Agency
- CDPHE Radon Program — Colorado Department of Public Health and Environment
- CDC Radon Health Information — Centers for Disease Control and Prevention
- American Lung Association Radon Overview — American Lung Association
Front Range homeowners wanting professional measurement instead of DIY can reach out for a vetted radon measurement contact across the nine-county service area.