Radon Testing in Englewood, CO | InspectandTest
Englewood 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. This older inner-ring Arapahoe County suburb just south of Denver has one of the metro’s oldest housing stocks, 1940s-to-1960s post-war ranches and bungalows, many with basements and crawlspaces in direct contact with soil. Radon is a colorless, odorless radioactive gas and the second-leading cause of lung cancer after smoking. This page explains how radon testing englewood homeowners should plan, why the local picture demands it, and what it costs. This summary reflects EPA and CDPHE guidance current as of 2026; consult a certified professional for testing decisions.
Radon testing in Englewood: 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 Englewood lies in Zone 1, a meaningful share of local homes test at or above that line. The only way to know your number is to test, since two homes a lot apart can read very differently depending on soil, foundation cracks, and how the house is sealed.
Short-term tests (2 to 7 days) suit real-estate timelines; long-term tests (90+ days) average seasonal swings for a fuller exposure picture. Our guide to radon testing across Arapahoe County covers the county-wide Zone 1 picture Englewood shares, and the plain-language radon guide for Front Range homeowners walks through both test types and the underlying science.
Englewood’s older housing makes radon entry easy to overlook. A 1950s ranch may have a partial basement, a crawlspace, or an aging slab with settling cracks, all paths radon uses to enter. Decades of foundation movement open new gaps over time, so an older Englewood home that never tested high years ago can read high today. Each home is its own case, which is why a neighbor’s clean result tells you nothing about yours.
Why Englewood homes need radon testing
Geology is the driver. Radon comes from the natural decay of uranium in soil, and the Front Range formations beneath Englewood and the South Platte corridor release it readily. The gas enters through slab cracks, control joints, crawlspace floors, sump openings, and the gaps around aging utility penetrations, then collects in the lowest level of the home.
Climate concentrates it. Colorado winters are cold, so Englewood homes stay sealed for months while furnaces create slight negative pressure that pulls soil gas indoors. The older partial basements and crawlspaces common in Old Englewood and Northwest Englewood are exactly the lower-level spaces where radon accumulates, and many have been finished into living space over the years.
Aging construction adds entry points. Decades of settling in a post-war ranch open new foundation cracks and widen old ones, and original crawlspaces with exposed soil let radon in directly. A family that finished a 1950s basement for extra living space may have unknowingly created the highest-exposure room in the house. That combination of soil contact and daily occupancy is the worst case for radon, which is why testing the lowest livable level matters in Englewood.
What an Englewood radon test covers
A professional test places a calibrated continuous radon monitor or passive device in the lowest livable level 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 Colorado 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 across Arapahoe County.
Continuous monitors versus passive kits
A continuous radon monitor logs hourly readings, so it can show whether someone opened a window 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 an Englewood home sale, the continuous monitor’s tamper detection and hour-by-hour record make it the preferred tool. For a homeowner’s own long-term picture, a passive kit left in place for months gives a more representative annual average.
Where the device goes
Placement decides whether the result reflects real exposure. The device belongs in the lowest level that is or could become living space, set roughly 20 inches or more above the floor, away from exterior walls, drafts, direct sun, and any sump or floor drain. In a 1950s Englewood ranch that often means a finished or partial 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 city.
Seasonal timing and re-testing in Englewood
Radon levels swing with the seasons, and Englewood’s climate sharpens that swing. Winter typically produces the highest readings because homes stay sealed for months and furnaces depressurize the lower level, pulling more soil gas indoors. A short-term test run in midwinter often shows an Englewood home near its annual peak, a conservative and useful number for a buyer weighing a mitigation request.
That variation is also why a clean test years ago does not guarantee a clean home today, a point that matters in aging Englewood housing. Decades of foundation settling open new cracks, a basement remodel changes airflow, and a new furnace alters the pressure that draws soil gas in. EPA guidance is to re-test every couple of years and after any major change. An Englewood household that finished a basement or replaced an HVAC system since the last test should measure again rather than trust an outdated number.
For a real-estate timeline, the short-term test wins on practicality, because it fits the inspection window and produces a documented closed-house result. A homeowner with no deadline can instead run a long-term test across heating and non-heating months for a truer annual average. Both are valid; the difference is whether the goal is a fast defensible number or a representative yearly picture of an older home’s exposure.
Radon testing cost in Englewood
A professional short-term radon test in the Englewood 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.
Weigh the cost against the protection. The EPA links thousands of lung-cancer deaths a year to radon, and Englewood’s Zone 1 status puts local exposure among the highest in the state. A $200 test that catches a 7 pCi/L 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.
The DIY-versus-professional choice usually comes down to purpose. For a homeowner’s own awareness, an inexpensive CDPHE-discounted kit gives a usable number for a few dollars plus lab fees and is a reasonable starting point. 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 an Englewood sale is worth it precisely because the stakes and the scrutiny are higher.
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. An Englewood 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 Englewood should not waive radon testing to sweeten an offer; the modest cost is small against the long-term health stakes of an untreated basement.
Neighborhoods and areas served
Radon turns up across Englewood regardless of neighborhood: the post-war ranches of Old Englewood and Broadway, the bungalows of Northwest Englewood, and the homes of Englewood Knolls. Service typically extends to adjacent Littleton, Sheridan, Cherry Hills Village, and south Denver, all within the same Zone 1 footprint where elevated readings are common.
The Zone 1 designation does not stop at a neighborhood line. The regional geology that drives radon is consistent across Englewood and its Arapahoe County neighbors, and the city’s older housing only adds entry points through settling foundations and crawlspaces. Wherever the home sits within Englewood, treating radon as a default test rather than an optional add-on reflects the reality that the entire city sits in the highest EPA risk zone.
How to choose an Englewood 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 Arapahoe County inspection or mold assessment can be efficient, but for a purchase the radon test itself should be the focus.
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 committing to mitigation. Either path beats not testing at all, since every Englewood home sits in Zone 1 and the only way to know your number is to measure it, especially in an older home where settling has opened new entry points over the decades.
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
Every Englewood 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.