Radon Gas Testing Service: A Plain-Language Guide
This guide summarizes EPA, CDC, and Colorado state guidance on radon testing current as of 2026; engage a NRPP-certified or CDPHE-listed testing provider for any testing decisions affecting real-estate transactions or family exposure. Professional radon gas testing services use continuous radon monitors (CRMs) under a 48-hour closed-house protocol and produce documented results suitable for real-estate transactions, post-mitigation verification, or family exposure assessment. Pricing in the Front Range Colorado market typically runs $100-300 for a single test. This guide covers when the service is worth the cost versus DIY kits, what protocols the service follows, and how to choose a certified provider.
What a professional radon testing service includes
A professional radon test starts with the technician deploying a continuous radon monitor (CRM) in the lowest livable area of the home. The CRM samples indoor air continuously for the test duration — typically 48 hours, sometimes extended to 96 hours for transactions requiring more conservative measurement — and records hourly radon concentrations. The technician also documents test conditions: outdoor temperature, barometric pressure, indoor temperature, HVAC operating status, and any unusual conditions (open windows, recent renovation, weather events).
The 48-hour closed-house protocol is the EPA standard for short-term radon testing. The home must be in closed-house conditions starting 12 hours before the test begins and continuing through the test period. Doors and windows remain closed except for normal entry and exit. HVAC operates normally. The closed-house protocol ensures the test measures typical indoor radon under realistic conditions rather than diluted concentrations from ventilation.
At test completion the technician retrieves the CRM, downloads the data, and produces a written report. The report typically includes hourly radon concentration data, the test average, environmental conditions during the test, and an interpretation against the EPA action level of 4.0 pCi/L.
How professional testing compares to DIY kits
DIY radon test kits run $15-30 for short-term charcoal or alpha-track kits sold through hardware stores and the Colorado CDPHE distribution program. The kits sit in the lowest livable area for 2-7 days (charcoal) or 90 days to 1 year (alpha-track) and then ship to a lab for analysis. Cost includes the lab analysis; results typically arrive 1-2 weeks after the kit ships back.
DIY kits are appropriate for initial homeowner screening. Professional CRM testing is appropriate for real-estate transactions, post-mitigation verification, and any situation requiring quick, documented results. The key differences are turnaround time (hours for CRM versus days to weeks for DIY), documentation (technician-signed report versus lab certificate alone), and the closed-house protocol verification that comes with a technician deployment.
For a deeper look at the test-kit options, see our home radon kit guide. The professional testing service complements rather than replaces DIY screening; many Front Range households use DIY testing for periodic monitoring and professional testing at specific decision points (purchase, sale, post-mitigation).
When professional testing is the right choice
Real-estate transactions are the most common driver of professional testing. Many lenders, real-estate contracts, and buyer-protection conventions require a CRM-based test rather than a DIY kit for transaction documentation. The technician-witnessed deployment, the controlled closed-house conditions, and the documented chain of custody all matter for transaction defensibility.
Post-mitigation verification is the second common use case. After a radon mitigation system installation, the homeowner needs to confirm the system has reduced indoor radon below the EPA action level. A professional CRM test 30-60 days after installation provides documented verification. This test is typically arranged through the mitigation contractor or a third-party tester.
Family exposure assessments after positive DIY screening are the third use case. When a DIY kit returns a result above the EPA action level, a confirmatory CRM test provides higher-confidence measurement before the family commits to mitigation system installation. The CRM test also surfaces variability that a single-period DIY kit cannot show.
NRPP and CDPHE certification
The National Radon Proficiency Program (NRPP) and CDPHE state certification are the relevant credentials for Front Range radon testing service providers. NRPP certification covers the testing professional individually; CDPHE certification covers the company and the individual technicians. Both certifications require initial training, examination, and continuing education to maintain.
Property owners should verify both certifications before engaging a testing service. NRPP maintains a public search at the AARST-NRPP website. CDPHE maintains a public list at the Colorado state radon program website. The certifications take 30 seconds to verify and protect against unqualified providers.
Mitigation contractors and testing providers are sometimes the same company. This can work fine when the firm has separate testing and mitigation departments with proper independence; it raises a conflict-of-interest concern when the same individual performs both pre-mitigation and post-mitigation testing on the same project. Third-party post-mitigation testing is best practice.
Cost factors for professional testing
Front Range professional radon testing typically runs $100-300 for a single test. Pricing varies with the testing duration (48-hour basic versus extended testing), the number of test locations (single basement deployment versus multiple locations across a multi-level home), the type of report (basic versus comprehensive with environmental conditions documentation), and the urgency (next-day deployment versus standard scheduling).
Real-estate transaction testing typically commands the higher end of the pricing range due to documentation requirements and scheduling pressure within the inspection-objection period. Owner-occupied family-exposure testing without transaction urgency often books at the lower end of the range.
Multiple-location testing is appropriate in larger homes or homes with mixed foundation types. A single test in a basement may not represent radon levels on upper floors or in slab-on-grade portions of the same home. Comprehensive multi-location testing runs $300-600 and surfaces the radon distribution across the home rather than at a single deployment point.
What the testing service does not include
The testing service measures indoor radon concentration; it does not perform mitigation, design mitigation systems, or remediate any findings. When the test returns a result above the EPA action level, the homeowner separately engages a certified mitigator for system design and installation. Some testing providers also offer mitigation services, but the testing and mitigation are typically separate contracts.
Water testing for radon is also separate. Professional radon-in-water testing uses a different sample protocol (collected at the home water supply, shipped to a specialty lab) and runs $50-100 per sample. Homes with private wells and elevated indoor radon should consider water testing alongside the indoor air test to identify whether well-water radon is contributing to the indoor exposure.
For a deeper read on the underlying radon-in-water concern, see our radon in water guide covering well-water radon and the secondary inhalation pathway during showering.
Selecting a Front Range testing provider
The selection workflow has four steps. First, verify NRPP or CDPHE certification through the public databases. Second, request the provider’s standard report format — a sample report shows whether the documentation meets the property owner’s needs (transaction defensibility, post-mitigation verification, or routine screening). Third, confirm the turnaround time fits the inspection-objection or other decision deadline. Fourth, compare pricing across two or three certified providers.
Buyers in real-estate transactions often arrange testing through the buyer’s home inspector if the inspector offers radon testing as an add-on. This bundling can save money but requires verification that the inspector or their testing subcontractor holds NRPP or CDPHE certification. Not every home inspector is certified for radon testing; the credential is separate from the home-inspection credentials.
For broader context on the radon mitigation pathway after testing, see our radon testing pillar guide for Front Range homeowners.
How CRM technology compares to alpha-track and charcoal
Continuous radon monitors measure radon by detecting alpha particle emissions in real time. The CRM contains a small detection chamber, an alpha particle counter, environmental sensors (temperature, humidity, barometric pressure, sometimes tamper detection), and a data logger. The result is hourly radon concentration data over the full test period rather than a single integrated average.
Alpha-track detectors use a passive plastic film that records alpha particle damage over the deployment period. The film is analyzed by counting the alpha tracks under microscope after the deployment ends. Alpha-track is highly accurate for long-term (3-12 month) testing but does not provide real-time data and cannot detect tampering during the test.
Charcoal canister kits absorb radon onto activated charcoal during the deployment period (2-7 days). The canister ships to a lab that measures the absorbed radon by gamma counting. Charcoal is appropriate for short-term screening but more sensitive to deployment conditions (humidity, temperature) than CRM or alpha-track.
For real-estate transactions, CRM is the standard because of the hourly data, the tamper detection, and the documented closed-house verification. DIY kits use either short-term charcoal or long-term alpha-track depending on the homeowner’s testing window.
Tamper detection and test integrity
Real-estate radon testing carries a tamper-detection concern that DIY testing does not face. Sellers occasionally try to defeat the test by opening windows during the deployment to dilute the indoor radon reading. Professional CRM units include environmental sensors that flag deviations from closed-house conditions — sudden temperature drops, humidity spikes, or pressure changes that suggest open windows.
The technician’s deployment also includes physical placement choices that reduce tamper risk: placing the CRM in a low-traffic location, securing the unit to the floor or a surface to detect movement, photographing the deployment, and documenting the closed-house instructions provided to the seller. A tester who finds tamper evidence during data review can void the test result and require a re-test under more controlled conditions.
Interpreting the test results
EPA’s radon action level is 4.0 pCi/L. Test results at or above 4.0 pCi/L warrant mitigation system installation. Results between 2.0 and 4.0 pCi/L fall in a gray zone where mitigation is recommended but not required by EPA guidance; many Front Range homeowners install mitigation at these levels because the lifetime risk of radon-induced lung cancer increases continuously with concentration.
Test results below 2.0 pCi/L are generally considered acceptable. EPA recommends retesting every 2 years for results in this range, since radon levels can change with home conditions, soil moisture, and seasonal HVAC patterns. Front Range homeowners with low initial test results should not assume the home will remain low without periodic retest.
Real-estate-transaction interpretation sometimes differs from owner-occupant interpretation. Buyers may request mitigation as part of the inspection-objection process even at results slightly below the 4.0 pCi/L threshold; sellers can choose to install mitigation as a transaction concession or push back on the request. The negotiation depends on local market norms and the broader inspection-objection list.
Seasonal variability and retesting
Indoor radon levels vary seasonally. Winter levels are typically higher than summer levels because homes are tighter and operate with less natural ventilation. Front Range homes commonly show winter readings 20-50% higher than summer readings at the same property.
The seasonal variability matters for interpretation. A summer test result of 3.5 pCi/L could correspond to winter levels exceeding 4.0 pCi/L; a winter test result of 4.5 pCi/L could correspond to summer levels below the action level. Buyers and homeowners interpreting marginal results should consider the test season and potentially commission a second test in the opposite season for fuller picture.
Long-term alpha-track testing (3-12 months) captures the full seasonal range in a single measurement. Front Range owner-occupants without a transaction deadline often pair an initial short-term professional CRM test with a long-term alpha-track follow-up to capture both immediate decision data and the longer-term average.
References
- EPA radon testing protocols and guidance — US Environmental Protection Agency
- CDC radon exposure and testing guidance — Centers for Disease Control and Prevention
- Colorado CDPHE radon program and certified testing providers — Colorado Department of Public Health and Environment
Front Range homeowners looking for a certified radon testing provider can get in touch through our contact page for a referral to an NRPP or CDPHE-certified tester in the Denver metro area.