Colorado radon test kits
Free radon test kits for Colorado homes
Lab-grade, mailed to your door, effectively free — a small deposit, fully refunded when your kit reaches the lab. And worth doing: 46.4% of the 237,408 Colorado homes tested came back at or above the EPA action level of 4 pCi/L. The program isn’t live yet — waitlist members get first kits.
Join the test-kit waitlistHow a charcoal radon test kit works
Radon is an invisible, odorless radioactive gas that seeps up from the soil into homes — Colorado’s Front Range sits on uranium-bearing granite, which is why our numbers run so high. You can’t see it or smell it; the only way to know your home is to measure it.
The kit itself is simple: a small container of activated charcoal. You open it in the lowest lived-in level of your home — the basement, if you have one — and let it sit for 2–4 days while the charcoal adsorbs radon from the air. Then you seal it and mail it the same day you finish. The lab measures the radioactive decay coming off the charcoal and calculates your radon level.
The same-day mailing isn’t fussiness — it’s physics. Radon’s half-life is only about 3.8 days, so the signal on the charcoal starts decaying the moment you seal the kit. Labs need it within roughly a week of test end, or there’s nothing reliable left to measure. (It’s also why a kit that’s been sitting in a garage for a season should just be replaced.)
Run the test with windows and doors closed as much as practical. The heating season gives the most conservative reading — but an imperfect summer test beats an untested home. If a summer number comes back elevated, winter will usually be higher.
Curious what levels look like around you first? See the statewide CDPHE radon data or look up radon levels by ZIP code.
Kit, monitor, or professional test?
Lab-analyzed kit (what we’re offering): a certified result at effectively zero cost. Certified matters — it’s what counts for a real-estate transaction, for verifying an existing mitigation system still works, and for deciding whether to spend real money on mitigation.
Consumer monitor (Airthings and similar): genuinely useful for watching trends — several of the repair calls our mitigation partner takes start with “my monitor’s 7-day average has been creeping up.” But no consumer monitor is a certified measurement. Monitor for trends; lab-test for decisions. (Monitor creeping up on a home that already has a system? Run this checklist.)
Professional CRM test: a calibrated continuous monitor placed by a certified tester, usually ~48 hours — the standard inside a real-estate inspection window, priced accordingly. Right when a transaction clock is ticking; more than most homeowners need for a first look.
Free radon test kits — coming soon
We’re putting together a radon test-kit program for Colorado homeowners: a lab-grade kit with a small $20 deposit that’s fully refunded the moment your kit reaches the lab — so the test ends up effectively free. It isn’t live yet. Drop your email and you’ll be first to know the day it launches.
Why a deposit on a free kit? Most free radon kits are never used — here’s the research →
- Lab-grade short-term kit
- $20 deposit, fully refunded
- Certified result you can act on
If your number comes back high
First: it’s fixable, and the fix is routine here. A sub-slab depressurization system — a fan and a pipe that vent soil gas above your roofline — reduces indoor radon by up to 99% in most homes, and a standard install in Colorado runs about $1,500. Half the homes on the Front Range have been through this.
If your kit comes back at or above 4 pCi/L, we connect you with an NRPP-certified Colorado mitigation team for a free quote — see how mitigation works and what it costs.
Radon test-kit FAQ
- Is the radon test kit really free?
- We're putting together a test-kit program for Colorado homeowners with a small $20 deposit that's fully refunded the moment your kit reaches the lab — so the test itself ends up effectively free, with a little skin in the game to make sure kits get used. It isn't live yet; join the waitlist and we'll email you the moment it launches.
- How does a charcoal radon test kit work?
- You open the kit in the lowest lived-in level of your home and let it sit for 2–4 days while activated charcoal adsorbs radon from the air. Then you seal it and mail it the same day — the lab measures the radioactive decay on the charcoal and reports your level. Because radon's half-life is only about 3.8 days, the kit must reach the lab within roughly a week of finishing, or the signal literally decays away.
- How long does radon testing take?
- A short-term charcoal kit measures for 2–4 days. Add shipping and lab analysis and you typically have a certified result within about two weeks of starting. Continuous monitors give faster feedback but aren't certified measurements.
- I have an Airthings or other radon monitor — do I still need a kit?
- Consumer monitors are genuinely useful for watching trends, but they aren't certified measurements — no consumer monitor is. A lab-analyzed kit gives you a certified result, which is what matters for real-estate transactions, verifying a mitigation system actually works, or deciding whether to spend money on one. Best practice: monitor for trends, lab test for decisions.
- When is the best time to test for radon?
- The heating season (fall through early spring) gives the most conservative reading — closed-house conditions concentrate radon, and short-term tests should be run with windows and doors closed as much as practical anyway. But an imperfect summer test beats an untested home: if a summer reading comes back elevated, it will usually read higher in winter.
- What radon level is considered dangerous?
- The EPA's action level is 4 pCi/L (picocuries per liter). At or above that level, the EPA recommends installing a mitigation system. There is no completely "safe" level of radon — risk rises with exposure — but 4 pCi/L is the threshold for action.
- How common is high radon in Colorado?
- Very common. Of 237,408 pre-mitigation indoor radon tests collected statewide by the Colorado Department of Public Health and Environment (2005–2025), 46.4% came back at or above the EPA action level. Much of the state sits in EPA Radon Zone 1, the highest-potential zone.
- What happens if my radon test comes back high?
- A mitigation system — typically sub-slab depressurization — reliably lowers indoor radon, usually to well below the action level. If your result is high, we connect you with an NRPP-certified Colorado mitigation team for a free quote.
Sources: U.S. EPA, A Citizen’s Guide to Radon & Home Buyer’s and Seller’s Guide; CDPHE Colorado Radon Tests 2005–2025; standard charcoal-kit lab protocols (exposure and return windows vary slightly by kit — follow your kit’s instructions).