When Should You Test Your Home for Radon? A Complete Guide
Radon is a colorless, odorless gas that seeps up from the soil beneath your home. This invisible gas is also the second leading cause of lung cancer in the United States. So the real question isn't whether radon testing matters; it's when to test.
When Should You Test Your Home for Radon?
There's no single rule for radon testing, but there are four clear moments to do it.
Your home has never been tested
You're buying or selling the property
You just finished (or are planning) a renovation
It's been two years since your last test
Each of these resets the clock, and each one is worth taking seriously on its own.
Never Been Tested? Start Here
If your home has no testing history, you're working blind. Radon levels vary block by block, even house by house in Denver. Your neighbor may have an existing mitigation system lowering their results, so their readings tell you nothing about yours. A first test gives you a baseline, and that baseline shapes every decision after it.
Buying or Selling: Why Agents Should Care
Radon testing matters to real estate agents as much as it does to buyers. A current radon test builds trust and can prevent last-minute negotiation headaches. Buyers get peace of mind, and sellers get a smoother path to closing. There are no surprises waiting during inspection week.
After a Renovation, Test Again
Finished a basement or added an addition to your Denver home? Construction changes airflow, and airflow changes how radon moves through a house. A test after the dust settles confirms whether those changes raised or lowered your levels, so you're not guessing.
The Two-Year Guidance
Radon levels aren't fixed. They shift with soil conditions, foundation settling, and even the weather. So a result from two years ago may not reflect today's reality. According to the EPA, retesting every two years keeps your information current and keeps small changes from turning into big surprises.
How Long Does a Radon Test Actually Take?
Short-term tests run for 48 hours and give you a quick snapshot of your home’s air quality. Long-term tests run for more than 90 days and capture how radon levels shift with seasons. Most home sales rely on short-term tests because of closing timelines. A long-term test gives the fuller picture, though, if you have the time.
What If Your Levels Come Back High?
The EPA recommends action at 4 pCi/L or higher, though even lower levels carry some risk. A high result doesn't mean panic. It means it's time to bring in a DORA-licensed radon professional. They can install a mitigation system and bring your levels back down to a safer range.
Radon will always be invisible, but the timing of your test doesn't have to be. Test when you move in, when you sell, when you renovate, and every two years after. Do that, and you'll never be caught off guard by something you couldn't see coming.
