Most people in Huntsville hear the word radon for the first time during a home purchase, when an inspector hands back a report with a number and the letters pCi/L. If you got here because of a number like that, or because a neighbor in Madison or Hampton Cove mentioned they had a system installed, this page walks through how radon testing works, which kind of test fits your situation, and how to read the result.
Why test a house in Madison County
Radon is a radioactive gas produced when uranium in soil and rock decays. It moves up through the ground and enters a house through slab cracks, plumbing penetrations, sump pits, and the joints where walls meet floors. Because a closed house pulls air from the soil, especially when the heat is running in winter, gas can build up indoors without anyone noticing. You can't see it or smell it. A test is the only way to know.
Madison County is a Zone 1 county on the EPA Map of Radon Zones, the highest of three categories. The Alabama Department of Public Health also lists Madison among the 15 Alabama counties with the highest radon potential. Those ratings describe the county as a whole. Two houses on the same Huntsville street can test very differently because of soil, foundation type, and how air moves through each home. That's why the EPA recommends testing every home, in every zone.
The number that matters: 4 pCi/L
Radon in air is measured in picocuries per liter (pCi/L). The EPA recommends fixing a home when the level is 4 pCi/L or higher, and suggests considering a fix when results land between 2 and 4 pCi/L. There is no level the EPA calls perfectly safe; 4 pCi/L is the point where it says action is clearly warranted.
Types of radon tests
Short-term tests (2 to 90 days)
Short-term tests are the usual first step. Charcoal canisters and similar passive devices sit in the lowest lived-in level of the house for a few days, then go to a lab. They are inexpensive and quick. Their weakness is that radon swings from day to day with weather and how the house is used, so a short test is a snapshot, not an annual average.
Long-term tests (more than 90 days)
Alpha-track and electret devices left in place for three months to a year give a better picture of your actual yearly exposure. Huntsville's mix of hot, humid summers with the AC running and cooler winters with the furnace on changes how much soil air a house draws in, so a long-term test smooths out those seasons.
Continuous radon monitors
Professionals often use continuous radon monitors (CRMs) that log readings every hour. They produce an hour-by-hour chart, flag tampering or open windows, and give results immediately at the end of the test. This is the standard tool for real estate deadlines, where a 48-hour test has to be finished and reported inside a short inspection window.
DIY kit or professional test?
A hardware-store kit is a perfectly reasonable first screen for a home you already own. Follow the instructions exactly, mail it promptly, and pay attention to the date the lab receives it. A professional test makes more sense when:
- You're buying or selling and the result has to stand up in a negotiation.
- A kit came back near or above 4 pCi/L and you want a confirming measurement before spending money on a system.
- You need a post-mitigation test to confirm a new system is working.
- The house has several foundation types, such as a basement under part of the house and a crawl space under an addition, and you want to know where the gas is coming from.
Certified measurement professionals follow published protocols for device placement, closed-house conditions, and quality control. In Alabama there is no state radon license, so ask whether the tester is listed with the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). ADPH points residents to those two national programs.
How to set up a good test
Whoever does the test, the conditions matter as much as the device:
- Keep windows and outside doors closed, except for normal coming and going, for at least 12 hours before the test and for the whole test.
- Run the HVAC normally, but don't use whole-house fans or window units that pull in outside air.
- Place the device in the lowest level you use regularly, at breathing height, away from drafts, exterior walls, kitchens, and bathrooms.
- Avoid testing during severe storms or unusually high winds, which can distort short-term results.
- Record the start and stop times and get the device to the lab right away.
Reading your result
If a short-term test comes back at 4 pCi/L or higher, the EPA suggests a follow-up test. A second short-term test averaged with the first, or a long-term test, helps confirm the level before you choose a fix. In a real estate deal, though, there often isn't time, and buyers and sellers usually negotiate on a single professional test.
If your result is below 2 pCi/L, you're in good shape, but it's worth retesting every couple of years and after major renovations, such as finishing a basement or replacing the HVAC system, since those changes can affect how air moves through the house.
Between 2 and 4 pCi/L is a judgment call. Many Huntsville homeowners in that range choose a long-term test over a full year before deciding.
What testing costs
Prices are set by each professional. As a general national reference, Angi's 2026 cost data puts professional radon testing at about $150 to $700, with do-it-yourself kits much cheaper. Those are typical national ranges, not local quotes. A Huntsville-area pro can give you an exact price after hearing about your house.
After a high result
A high test isn't a reason to panic or to move out. It's a common, fixable problem. The usual fix is a fan-powered vent system that pulls soil gas from under the house and exhausts it above the roof. See radon mitigation systems for how those work, or crawl space mitigation if your home sits on piers or a crawl space.