Why Radon Testing Is More Important Than You Think (And How to Do It Right)
Published July 29, 2025 | Updated November 17, 2025
Photo by Clay Banks
Most people test for radon when they're buying a house—because it’s required by the inspector. Then, they never think about it again, and I understand why! It’s boring and if the reading was negative, there are so many other things to spend your time and money on when moving into a new place.
But radon isn't a one-time concern. It's an ongoing indoor air quality issue that changes over time, and most homeowners are testing for it completely wrong.
The Problem With How We Currently Test for Radon
The standard practice in real estate is to use a short-term radon test kit—usually a 2-4 day test during the home inspection period. However, a 2019 University of Calgary study found that 99% of short-term radon tests are inaccurate compared to long-term monitoring. Radon levels fluctuate dramatically day-to-day and season-to-season. You could test on a low radon week and get a false sense of security, or test on a high radon week and panic unnecessarily. (I have personally done the unnecessary panic once before, and the radon mitigation company I called explained to me that I needed to get a longer average before they sent someone out. This is why I have a continuous monitor now!)
This matters because radon is the second-leading cause of lung cancer in the United States, responsible for 21,000 deaths annually. It's also the leading cause of lung cancer among non-smokers. Unlike other home hazards that cause immediate symptoms, radon is completely invisible, odorless, and symptomless—until decades of exposure lead to cancer. (This is why I worried!)
What Makes Radon Different From Other Indoor Air Pollutants
Radon is a radioactive gas released from the natural decay of uranium in bedrock, particularly granite, limestone, and shale. As it rises from the ground, it enters homes through foundation cracks, crawlspaces, and gaps around pipes. In tightly-sealed, energy-efficient modern homes, it gets trapped and accumulates to dangerous levels.
Here's what makes it uniquely dangerous from a medical perspective:
It causes no acute symptoms. You won't get headaches, dizziness, or breathing problems from radon exposure. The radioactive particles can attach to dust, lodge in lung tissue when inhaled, and cause DNA damage over years or decades. By the time you develop a persistent cough, chest pain, or cough—symptoms of radon-induced lung cancer—it’s too late.
But the long term risks are serious. At 4.0 pCi/L, a lifelong non-smoker has a 7 in 1,000 chance of developing lung cancer. For smokers, that risk jumps to 62 in 1,000. Emerging research also links radon exposure to childhood leukemia and certain birth defects, even at levels below 4.0 pCi/L.
Why Your Zip Code Doesn't Tell You Enough
The EPA publishes a Map of Radon Zones showing county-level risk, and it's a useful starting point. But radon levels vary wildly house-to-house, even on the same street. Your neighbor could have 0.8 pCi/L while you have 8.0 pCi/L, depending on your specific geology, foundation construction, and ventilation. You cannot assume your home is safe without testing.
This is especially true if you:
Live in a home with a basement or crawlspace
Have made your home more airtight (new windows, insulation, HVAC upgrades)
Use well water (radon dissolves into groundwater and releases into your air during showers)
Burn natural gas indoors (another radon source)
How to Actually Test for Radon (The Right Way)
If you want an accurate picture of your radon exposure, you need long-term monitoring—either a 90-day test kit or, ideally, a continuous radon monitor that tracks levels year-round.
Short-term tests (2-7 days) are useful for quick screening—if you're buying a house or suspect a sudden problem—but should always be confirmed with long-term testing. They're inexpensive and widely available, but unreliable as your only data point.
Long-term tests (90 days to 1 year) smooth out daily and seasonal fluctuations and give you a true average. These are more accurate than short-term kits, but you're still only getting a snapshot in time.
Continuous digital radon detectors provide real-time readings and track trends over months and years. They cost more upfront ($100-300), but they're the most accurate way to monitor radon—especially after you've made changes to your home's insulation, HVAC, or foundation that could affect levels. Many models send alerts to your phone if levels spike. They also give you the greatest peace of mind, which is why I chose one.
One problem: finding an actually accurate radon monitor in the U.S. is surprisingly difficult! Unlike professional radon measurement devices used by inspectors, consumer-grade monitors aren't required to meet any accuracy standards in the United States. There's no FDA oversight, and no EPA certification for home devices. I had to turn to the Canadian National Radon Proficiency Program (C-NRPP) to find third-party tested monitors that have actually been verified for accuracy. Most of the monitors on the market have never been independently validated, which means you could be making health decisions based on faulty data.
For a detailed breakdown of which radon detectors are most accurate and which ones I recommend based on your situation, see my full guide to the best radon detector kits here.
Photo by Clay Banks
What to Do If Your Levels Are High
If your radon test comes back at or above 4.0 pCi/L, the fix is straightforward: radon mitigation. When properly installed by a certified professional, these systems reduce radon by 50-99%, often bringing levels below 2.0 pCi/L.
Costs typically range from $700-$1,300 depending on your home's construction. It's a one-time investment that dramatically reduces your long-term cancer risk—far less expensive than cancer treatment.
Even if your levels are between 2.0-3.9 pCi/L (below the EPA action level but above outdoor background), mitigation is worth considering, especially if you're a smoker or planning to live in your home long-term.
The Bottom Line: Test Now, Test Continuously
Radon testing shouldn't be a one-time checkbox during a home inspection. It should be part of your ongoing home safety routine, just like checking smoke detectors or carbon monoxide alarms.
Start by testing your home's lowest lived-in level (basement or ground floor). If you're using a short-term kit, follow up with a long-term test. Better yet, invest in a continuous monitor so you can track changes over time and verify that any mitigation system you install is actually working.
For my recommendations on the most accurate radon detectors—including portable monitors, continuous trackers, and budget-friendly options—visit my complete radon detector guide here.
Reducing radon is one of the most effective forms of cancer prevention available to you. Unlike genetic risk factors you can't control, this is a hazard you can detect, measure, and fix. Take the time to test properly.
Sources:
U.S. Environmental Protection Agency – Health Risk of Radon, epa.gov
ScienceDaily – Short-term radon test kits are not effective (University of Calgary, 2019), sciencedaily.com
Cleveland Clinic – Radon Gas: Causes, Exposure, Symptoms & Complications, my.clevelandclinic.org
Oregon State University News – Radon and Childhood Leukemia Study, news.oregonstate.edu
Langlois et al., Birth Defects Research (2016) – Radon and Birth Defects, pubmed.ncbi.nlm.nih.gov
