Radon Testing in Northglenn, Colorado | InspectandTest
Northglenn sits in EPA Radon Zone 1, the agency’s highest-risk category, where the predicted average indoor level meets or exceeds the 4 pCi/L action threshold. Built as a planned post-war suburb in the 1950s and 1960s on the flat, uranium-bearing plains soil of Adams County, the town has thousands of finished-basement homes where radon can concentrate. Radon is a colorless, odorless radioactive gas and the second-leading cause of lung cancer after smoking. This page explains how radon testing northglenn homeowners should plan, why the local picture demands it, and what testing costs. This summary reflects EPA and CDPHE guidance current as of 2026; consult a certified professional for testing decisions.
Part of our Radon Levels guide — start there for the full picture →
Radon testing in Northglenn: what to know
Radon testing measures the gas accumulated inside a home in picocuries per liter (pCi/L). The EPA recommends action at or above 4 pCi/L, and because Northglenn lies in Zone 1, a meaningful share of local homes test at or above that line. Two neighboring homes on the same Stonehocker street can read very differently depending on foundation cracks and soil contact, so the only way to know your number is to test.
Short-term tests of 2 to 7 days fit real-estate timelines, while long-term tests of 90 days or more average seasonal swings for a fuller exposure picture. For the underlying science and device types, our plain-language radon guide for Front Range homeowners walks through both approaches.
House-to-house variation is the reason a neighbor’s clean result tells you nothing about your own. Radon depends on the uranium in the soil directly under a foundation, the number and size of slab cracks, and how hard the furnace pulls air. Two 1960s ranches a lot apart in Original Northglenn can read 2 pCi/L and 8 pCi/L for exactly these reasons, which is why testing is always an individual-home decision.
Radon levels also change over time, so a clean test from years ago does not guarantee a clean home today. Foundation settling opens new cracks, a basement remodel changes airflow, and a new high-efficiency furnace alters the pressure that draws soil gas indoors. EPA guidance is to re-test every couple of years and after any major change to the home. A Northglenn household that finished a basement or replaced an HVAC system since its last test should measure again, because the old number may no longer describe the current home.
Why Northglenn homes need radon testing
Geology drives it. Radon comes from the natural decay of uranium in soil and rock, and Northglenn’s flat plains soil carries enough uranium to feed elevated indoor levels across Adams County. The town’s dominant 1950s and 1960s housing puts finished-basement living space in direct contact with that soil, where radon enters through slab cracks, control joints, and sump openings.
Climate concentrates it. Colorado winters keep Northglenn homes sealed for months, and furnaces create slight negative pressure that pulls soil gas indoors. Finished basements in Hillcrest, Fox Run, and Original Northglenn are exactly the lower-level spaces where families spend time and where radon collects. Even when a swamp cooler runs in summer and exchanges some air, the long sealed winter is when readings climb.
The finished-basement pattern is what makes radon a genuine occupancy concern here. A basement bedroom or rec room is both the lowest, most soil-contacted space and a place where people spend hours daily. That combination of maximum soil contact and maximum time is the worst case for exposure. A family that finished a 1960s basement to gain living space may have unknowingly created the highest-exposure room in the house, which is exactly why testing the lowest livable level matters.
The sealed-winter pattern deserves emphasis because it is when readings peak. From late fall through early spring, Northglenn homes stay closed, the furnace runs, and the stack effect pulls soil gas up through every slab crack and floor-wall joint. A test run in deep winter often shows the highest number a home will produce, which is why short-term tests for real-estate decisions are typically scheduled under closed-house conditions that mimic that worst case. Testing in an open-windowed summer week can understate the exposure a family actually experiences the rest of the year.
What a Northglenn radon test covers
A professional test places a calibrated continuous radon monitor or passive device in the lowest livable level, usually a finished basement or ground-floor room, under closed-house conditions. The tester documents placement and the closed-house window so the result holds up if it feeds a real-estate negotiation.
Closed-house conditions
For at least 12 hours before and during a short-term test, windows and exterior doors stay closed except for normal entry. This keeps a breezy plains afternoon from artificially lowering the reading. If a test comes back at or above 4 pCi/L, the next step is mitigation, detailed in our guide to radon mitigation in Northglenn.
Continuous monitors versus passive kits
A continuous radon monitor logs hourly readings, so it can show whether a window opened mid-test or whether levels spiked overnight, evidence that protects a buyer from a tampered result. Passive devices like charcoal canisters average exposure and mail to a lab at lower cost. For a Northglenn home sale, the continuous monitor’s tamper detection and hour-by-hour record make it the preferred tool, while a passive kit left for months gives a homeowner a representative annual average.
Where the device goes
Placement determines whether the result reflects real exposure. The device belongs in the lowest level that is or could become living space, set about 20 inches or more above the floor, away from exterior walls, drafts, direct sun, and sumps or floor drains. In a typical Northglenn ranch that means the finished-basement family room rather than an unfinished mechanical corner. Testing a space no one occupies understates the exposure a family actually experiences, while testing the lowest livable level captures the worst-case room, the conservative and correct approach for a Zone 1 town.
Radon testing cost in Northglenn
A professional short-term radon test in the Northglenn market typically runs about $135 to $250. A do-it-yourself kit costs roughly $15 to $40 plus lab fees, and CDPHE periodically offers discounted kits to Colorado residents. Bundled into a pre-purchase home inspection, radon testing often adds just $100 to $175 instead of a separate trip charge.
Long-term kits sit at the low end on price but tie up months. For a transaction, the documented short-term professional test is standard because it fits inspection deadlines and produces a defensible closed-house result.
The choice between DIY and professional usually comes down to purpose. For a Northglenn homeowner’s own awareness, an inexpensive CDPHE-discounted kit is a reasonable starting point and gives a usable number for a few dollars plus lab fees. For a real-estate transaction, the professional continuous-monitor test is the standard because its tamper detection, documented placement, and defensible result hold up when the number drives a mitigation request. Spending a bit more for the professional test in a sale is worth it precisely because the stakes and the scrutiny are higher.
Weigh the cost against the protection. The EPA links thousands of lung-cancer deaths a year to radon, and Northglenn’s Zone 1 status puts local exposure risk among the highest in the state. A $200 test that catches a 7 pCi/L finished-basement reading lets a family install a roughly $1,500 mitigation system and cut exposure by 90 percent or more. Skipping the test leaves the risk invisible for as long as the family lives there.
Colorado regulations and disclosure
Colorado requires radon disclosure in residential real-estate transactions, and the Seller’s Property Disclosure asks sellers to report known radon results and any existing mitigation system. CDPHE runs the state radon program, references the 4 pCi/L EPA action level, and offers discounted kits to residents. Colorado does not license home inspectors, so for any test tied to a sale, confirm the tester follows recognized national measurement protocols rather than assuming a license guarantees competence.
Disclosure shapes negotiations both ways. A seller who has tested and mitigated can offer a clean post-mitigation result as reassurance, while a seller who has never tested leaves the buyer to discover the number during the contingency, often resulting in a mitigation credit. Buyers in Zone 1 Northglenn should not waive radon testing to sweeten an offer; the modest cost is small against the long-term health stakes of an untreated finished basement.
For sellers, testing ahead of listing can be a smart move. Knowing the number lets a seller mitigate proactively and market a clean, documented result, removing a common point of friction during the inspection period. A buyer who sees a verified post-mitigation reading has one less thing to negotiate, and the seller controls the cost and timing of the fix rather than scrambling under a contract deadline. In a Zone 1 suburb where elevated readings are common, getting ahead of the radon question often smooths the whole transaction.
Neighborhoods and areas served
Radon turns up across Northglenn regardless of neighborhood: finished-basement homes in Original Northglenn, Stonehocker, Hillcrest, and Fox Run all sit on the same uranium-bearing plains soil. Service typically extends to adjacent Thornton, Westminster, Federal Heights, and Broomfield, all within the same Zone 1 footprint where elevated readings are common.
The consistency of the risk is the practical takeaway. Whether a home is an original 1950s build near Webster Lake or a slightly later ranch in Fox Run, the uranium-bearing plains soil beneath it is the same, and the finished-basement habit is the same. That is why local providers treat radon as a default test in Northglenn rather than a special-case add-on reserved for homes with obvious symptoms, because radon has none.
Because the regional geology is consistent across Adams County, the Zone 1 designation does not stop at a subdivision line. Owners comparing the wider picture can read our overview of radon testing across Adams County, or look at a neighboring city such as radon testing in Thornton. Wherever a home sits in Northglenn, treating radon as a default test rather than an optional add-on reflects the reality that the whole town is in the highest EPA risk zone.
How to choose a Northglenn radon testing provider
Ask whether the provider uses a calibrated continuous radon monitor and follows EPA or AARST protocols. A good tester documents closed-house conditions, device placement, and test duration so the result stands up in a sale. Bundling radon with a full home inspection in Northglenn is efficient and gives buyers one coordinated report on both the structure and the soil-gas risk.
Confirm the monitor’s calibration is current and, for a purchase, ask the provider to place and retrieve the device themselves rather than handing you a kit, since a tester-administered continuous monitor carries far more weight in a negotiation. If a result comes back borderline, between 2 and 4 pCi/L, a competent provider explains your options, including a follow-up long-term test, rather than pushing an unnecessary mitigation sale.
For homeowners not in a transaction, a CDPHE discounted long-term kit is a low-cost way to get a representative annual average, and it is a reasonable first step before deciding whether to bring in a professional. If that kit comes back at or near the action level, a professional follow-up confirms the result with calibrated equipment before you commit to mitigation. Either path is far better than not testing at all, since every Northglenn home sits in Zone 1 and the only way to know your number is to measure it.
References
- Radon risk and EPA zone maps — U.S. Environmental Protection Agency
- Colorado radon program and kits — Colorado Department of Public Health and Environment
- Radon and lung cancer — Centers for Disease Control and Prevention
Frequently asked questions
Is Northglenn in a high radon zone?
Yes. Northglenn sits in EPA Radon Zone 1, the highest-risk category, like the rest of Adams County. Every home, especially those with finished basements, should be tested.
What radon level requires action in Northglenn?
The EPA action level is 4 pCi/L. At or above that reading, EPA and CDPHE recommend mitigation. Levels between 2 and 4 pCi/L are still worth considering for reduction.
How much does a radon test cost in Northglenn?
A professional short-term test typically runs $135 to $250, while DIY kits cost about $15 to $40 plus lab fees. CDPHE periodically offers discounted kits to Colorado residents.
Why do Northglenn's finished basements matter for radon?
Finished 1960s basements put living space in direct contact with soil, where radon enters through slab cracks, and they are where families spend time, so the gas concentrates where occupancy is highest.
Can two neighboring Northglenn homes have different radon levels?
Yes. Radon depends on soil uranium content, foundation cracks, and how the home is heated and sealed, so identical ranches a lot apart can read very differently. A neighbor's clean test does not predict yours.
Every Northglenn home sits in EPA Zone 1, so radon testing is basic due diligence, not optional. To connect with a vetted local tester before your purchase deadline or this heating season, get in touch 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 |