Radon is a naturally occurring radioactive gas produced as uranium in soil and rock breaks down. It enters homes through foundation cracks, sump pits and slab penetrations, and concentrates indoors. Colorado, including El Paso County, sits in a high radon-potential zone, so testing is recommended for every home regardless of age.
What radon actually is
Uranium occurs naturally in soil and rock. As it decays over geological time it produces radium, and radium decays into radon — a gas. That gas moves through soil and finds its way into the air. Outdoors it disperses to harmless concentrations almost immediately. Indoors it does not.
A house is slightly depressurized relative to the ground beneath it, particularly in winter when warm air rising inside draws replacement air in at the bottom. That pressure difference actively pulls soil gas through whatever openings exist, and the house holds it. Long-term exposure to elevated indoor radon is a recognized lung cancer risk and the reason public health agencies recommend testing universally.
Why Colorado specifically
The state's geology — granitic rock and uranium-bearing soils across much of the Front Range — produces more radon than most of the country. Colorado sits broadly in the highest radon-potential classification, and El Paso County is within that zone. That does not mean every house here has a problem; radon levels vary enormously between neighbouring houses depending on soil, foundation construction and how the house breathes. It does mean the base rate is high enough that testing should be the default rather than something you do only if you have a reason to suspect it.
How it gets in
- Cracks in slabs and foundation walls, including hairline ones
- The gap where the slab meets the foundation wall
- Open or poorly sealed sump pits — a direct opening into the soil beneath the house
- Penetrations where plumbing, electrical or HVAC pass through the slab
- Crawlspaces with exposed earth floors
- Floor drains without a maintained trap seal
Note how many of those are plumbing-adjacent. An uncovered sump pit is both a radon entry path and the thing sitting in your basement, which is why sealed sump covers come up in both conversations.
Testing
Short-term test kits sit in the lowest lived-in level of the home for a few days under closed-house conditions and go to a lab. They are inexpensive and widely available, including through county public health programmes. Long-term tests run 90 days or more and give a better picture, because radon fluctuates with weather, season and how much the house is closed up. Winter readings tend to run higher — the stack effect is stronger and the windows are shut.
The EPA action level is 4.0 picocuries per litre. Between 2.0 and 4.0, reduction is worth considering. Testing after any foundation work, after significant air-sealing or window replacement, or after finishing a basement is sensible, because all of those change how the house breathes.
What reduces it
The standard approach is sub-slab depressurization: a pipe through the slab connected to a continuously running fan that vents above the roofline, so soil gas is drawn out before it can enter. This is a specialised trade with its own certification, and it is the right call when a test comes back elevated. It is not an HVAC job and we will say so plainly.
Where building systems do contribute:
- Sealing the obvious entry points. A sealed sump cover, sealed slab penetrations and properly maintained floor drain traps all reduce the easy paths in. Worth doing regardless.
- Balanced ventilation. An HRV or ERV brings in filtered outdoor air and exhausts stale indoor air at matched rates. It dilutes indoor contaminants generally and avoids the depressurization that unbalanced exhaust-only ventilation creates.
- Not making it worse. Large exhaust appliances — range hoods, whole-house fans, some dryers — depressurize a house while they run, which increases soil gas entry. This matters most in tight homes, and it is part of why combustion appliances need adequate make-up air.
What will not fix it: an air purifier. Radon is a gas, not a particle, so filtration does nothing for it. Be sceptical of anything sold as a radon solution that plugs into a wall.
Where this sits in the bigger picture
Radon belongs in the same conversation as the rest of your indoor air: filtration for particulates, ventilation for stale air and VOCs, humidity control for comfort, and a working CO alarm for combustion safety. Our piece on what indoor air quality actually means covers how these interact, and why we assess before recommending anything explains our approach. For ventilation and filtration, see indoor air quality services.
For radon testing and mitigation itself, start with the Colorado Department of Public Health and Environment or El Paso County Public Health — both maintain guidance and, at times, low-cost test kit programmes.
Frequently asked questions
Is radon a problem in Colorado Springs?
Colorado sits in a high radon-potential zone because of uranium-bearing soils and granitic rock, and El Paso County is within it. Levels vary substantially between neighbouring homes depending on soil, foundation type and how the house breathes, so the only way to know a specific home's level is to test it.
How do I test my home for radon?
Place a short-term test kit in the lowest lived-in level of the home for several days under closed-house conditions and send it to a lab, or use a long-term test running 90 days or more for a better average. Colorado and El Paso County public health agencies publish guidance and sometimes offer low-cost kits.
Can an air purifier remove radon?
No. Radon is a gas rather than a particle, so filters and purifiers designed to capture dust, pollen and smoke do nothing to reduce it. Reducing radon requires keeping soil gas out of the house — typically a sub-slab depressurization system installed by a certified radon mitigation contractor.
Do newer homes have less radon?
Not necessarily, and sometimes the opposite. Newer homes are built tighter, so while less soil gas may leak in, less of what does get in is diluted by natural air exchange. Radon depends on local geology, foundation construction and pressure differences rather than the age of the house.