DIY Radon Reduction: What Works and What Does Not
Homeowners in Larimer and Weld Counties often ask the same practical question: how much of a radon problem can they handle themselves, and where does that end? The honest answer separates measurement, which you can absolutely do on your own, from mitigation, which Colorado law treats very differently once money changes hands. This guide walks through both, so you know which weekend projects are worth your time and which ones will not move the needle in a Zone 1 region where soil gas pressure is high.
Northern Colorado sits entirely inside EPA Radon Zone 1, the highest-potential category, where the predicted average indoor screening level runs above 4.0 pCi/L. That geology matters for DIY expectations. In lower-risk regions a small ventilation change might tip a borderline home under the line. Here, the soil is working against you, so it pays to be realistic about what a homeowner can and cannot accomplish alone.
What you can do yourself
Testing is genuinely DIY
Measuring radon is the one part of this process that does not require a professional at all. A short-term test kit is inexpensive, widely available, and accurate when you follow the instructions. CDPHE, which runs Colorado’s state radon program, offers discounted test kits and public guidance. Place the kit in the lowest level you regularly use, keep windows and exterior doors closed as the kit directs, and send it to the listed lab.
If you want a fuller picture, run a long-term test (more than 90 days), which averages out the daily and seasonal swings that a short-term test can miss. Either way, the number you get back is what drives every decision that follows. For more on reading that number, see our radon test results guide and the overview on our radon testing page.
Sealing and small fixes help modestly
There are real, useful things a homeowner can do that reduce radon entry, even if they rarely solve an elevated level by themselves:
- Seal visible cracks in the slab and foundation walls with the right caulk or polyurethane.
- Cover and seal sump pits with an airtight, gasketed lid.
- Close gaps around pipe and utility penetrations through the floor.
- Cover exposed soil in a crawl space with heavy plastic sheeting.
- Improve basement and crawl space ventilation where it is safe to do so.
These steps cut down some of the pathways soil gas uses and can make a professional system work more efficiently later. They are worth doing. Just do not expect them to carry the whole load in a Zone 1 home.
What does not reliably work
The trouble with a seal-only approach is that radon is a pressure-driven gas. Your house acts like a chimney, and the lower pressure inside pulls soil gas up through whatever openings remain. You can caulk the cracks you can see, but the gas finds the ones you cannot. That is why EPA does not recommend sealing as a standalone method. It is a supporting measure, not a fix.
A few other popular ideas fall short too. Running exhaust fans or cracking windows may lower a reading while they run, but the effect disappears the moment you stop, and depressurizing the house can actually pull in more soil gas. Consumer air purifiers do not remove radon in any meaningful way. Painting or applying a sealer coating to a basement floor is not a reliable radon barrier. None of these should be counted on to bring a confirmed high result down and keep it there.
The pattern is consistent: DIY measures nibble at the edges of the problem. In a region where about half of Colorado homes exceed 4.0 pCi/L, according to CDPHE, the edges are usually not enough.
Why does the ceiling on DIY matter so much? Radon is the second leading cause of lung cancer in the United States after smoking, and the leading cause among people who have never smoked, per CDPHE. A partial reduction that leaves a home hovering near the action level is not the same as getting it reliably below the line. That gap between “a little lower” and “consistently safe” is exactly the space a licensed mitigation system is built to close, and it is the reason the honest advice for a confirmed high result is to stop tinkering and get a real quote.
Crawl space homes deserve a special note here. If your home sits over a crawl space rather than a slab, covering exposed soil with plastic is a reasonable DIY step, but a full crawl space solution usually pairs a sealed vapor barrier with a fan tie-in, and inaccessible crawl spaces can need air-exchange equipment. Our crawl space and basement radon page covers that in more detail.
Why paid installation requires a licensed professional
Here is the part that surprises people. In Colorado, whether you can pay someone to install a radon system is not just a quality question, it is the law. House Bill 21-1195, the “Regulation of Radon Professionals” act, created two state license types (radon measurement and radon mitigation) through the DORA Division of Professions and Occupations. Licensure has been mandatory since July 1, 2022, and since that date, performing radon measurement or mitigation for pay without a license is prohibited.
That means paying an unlicensed handyman to install a mitigation system is not allowed in Colorado, regardless of how handy they are. You can read the bill text at leg.colorado.gov, and you can confirm any professional’s credential on the state license lookup.
To be clear about the boundary: you are free to work on your own home. The license requirement applies to paid work performed for others. So the practical takeaway is simple. Do your own testing. Do your own sealing. But when it comes to a paid mitigation install, the person doing it must hold a Colorado radon mitigation license. NoCo Radon Pros does not hold that license and is not a contractor. We are a free matching service that connects you with an independent, state-licensed radon professional, and the license belongs to that professional, never to us.
What a professional system actually does
A licensed installer typically fits an active sub-slab depressurization system: a sealed suction point through the slab, PVC piping routed up and out, and a continuously running fan that pulls soil gas from beneath the foundation before it can enter the living space. This is the method that reliably brings and holds a home below the action level, which is why it is the standard recommendation in Zone 1. You can learn more on our radon mitigation page.
When to stop the DIY track
EPA sets the action level at 4.0 pCi/L and advises fixing at or above that figure, with a suggestion to consider action between 2.0 and 4.0 pCi/L. Use that number as your dividing line. If your own test comes back at 4.0 pCi/L or higher, that is the trigger to move from weekend projects to a licensed professional.
Cost is often the next worry, and the range is more reasonable than many expect. Most homes fall between $1,000 and $2,500, with about $1,500 common for a standard sub-slab system. Colorado also runs a low-income mitigation assistance program that can cover a certified system, and some utility customers may qualify for a rebate. Our mitigation cost guide breaks down the numbers, crawl space differences, and assistance options.
If you are selling or renting, the stakes go up because Colorado’s disclosure law (a bold-faced radon warning plus known radon information) attaches to those transactions. Our Colorado radon law guide covers the full picture, and you can always reach us through the contact page when you are ready to be matched with a licensed professional near you.