Radon Testing in Denver
Testing is the only way to know your level, and Denver residents can often get the kit for free. Here's how to test the way Colorado's health department recommends.
Free kits
Free, while supplies last
Denver residents can order a free kit from the city's public health department, and CDPHE offers one free kit per household per year. If both are out, CDPHE sells discounted kits.12
Your three ways to test
Free
Public health kit
Order through Denver's Department of Public Health & Environment or CDPHE's statewide order form while supplies last. CDPHE handed out more than 12,500 free kits in early 2025.123
Around $150
Licensed professional
CDPHE says hiring a licensed measurement professional is a good idea in a real estate deal, because it's the best way to be sure the test is valid.2
How CDPHE says to run a short-term test
- Close up the house 12 hours ahead.Shut exterior windows and doors 12 hours before starting, and keep them closed. Normal coming and going is fine, and most heating and AC can run as usual.4
- Run it at least 48 hours.The test should last a minimum of 2 days.4
- Photograph the serial number.It's on the white barcoded sticker, and you'll need it to register the kit and get results.4
- Log the start and end times,then mail the kit as instructed.4
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CDPHE's guide for do-it-yourself short-term kits in a home without a mitigation system:2
| Result | What CDPHE says to do |
|---|---|
| Green: under 2 pCi/L | Retest in 5 years. |
| Yellow: 2–3.9 pCi/L | Consider a long-term test. Consider mitigating if someone in the home is at high risk for lung cancer. Otherwise retest in 5 years. |
| Red: 4 pCi/L or more | Confirm with a second test and reduce levels with a mitigation system. If you're close to 4, a long-term test gives the best average. |
DDPHE recommends retesting every 2–3 years because conditions change.1 If you already have a system, CDPHE says to retest in 2 years when under 2 pCi/L, and to call a licensed pro if you're at 4 or higher.2
Why smokers should test first
CDPHE says the lung cancer risk from radon is almost 10 times higher for people who currently smoke than for people who never have.2 Denver's health department puts it at roughly 10 to 15 times.1
Renters and buyers
- Renters may test their own units under Colorado law. If you get a high result, CDPHE says to notify your landlord in writing.42
- Buyers are encouraged to test during the inspection. CDPHE recommends a licensed measurement professional using a continuous radon monitor or another approved device.4
Common questions
How do I get a free radon test kit in Denver?
Denver residents can order one online from the Denver Department of Public Health & Environment while supplies last. CDPHE also offers one free kit per household per year through its statewide order form.
How long should a radon test run?
CDPHE says a short-term test should run at least 2 days (48 hours), with windows and exterior doors closed starting 12 hours before the test.
What if my result is between 2 and 4 pCi/L?
CDPHE suggests a long-term test to learn your average. Consider mitigation if someone in the home is at high risk for lung cancer. Otherwise retest in 5 years.
How often should I test my Denver home?
DDPHE recommends testing every 2–3 years because conditions change. CDPHE's guide says to retest in 5 years after a result under 2 pCi/L in a home without a system.
Can I test my apartment if I rent?
Yes. Colorado law allows tenants to test their own units. If the result is high, CDPHE says to notify the landlord in writing.
Should a buyer use a professional tester?
CDPHE encourages buyers to hire a licensed radon measurement professional with a continuous radon monitor or other approved device during the inspection.
General information summarized from the public sources listed below. It isn't professional, medical or legal advice. A licensed professional who inspects your home can tell you what it needs.