You opened your radon report, saw a number above 4.0, and now you’re wondering what it means for your family and your home. Take a breath. When a radon test comes back high, it’s a common result in our part of North Carolina, it can be measured precisely, and it’s one of the more fixable problems a house can have. Here’s how to read high radon test results, when to retest, and what happens next if your home needs a radon mitigation system.
What Does a High Radon Test Result Actually Mean?
In the U.S., radon results are reported in picocuries per liter of air (pCi/L), a measure of how much radioactivity from radon is in each liter of the air you breathe at home. Your report shows the average over the time the test device was running.
The key benchmark is the EPA action level of 4.0 pCi/L. EPA recommends fixing a home when radon is at or above that level. Because there is no known safe level of radon exposure, EPA also recommends that homeowners consider fixing their home when results fall between 2 and 4 pCi/L. For context, EPA estimates the average indoor radon level in American homes is about 1.3 pCi/L, and outdoor air averages about 0.4 pCi/L.
What If My Report Shows Bq/m³ Instead of pCi/L?
Some digital monitors display radon in becquerels per cubic meter (Bq/m³), the unit used in most other countries. The conversion is simple: 1 pCi/L equals 37 Bq/m³. Multiply a pCi/L number by 37 to get Bq/m³, or divide a Bq/m³ number by 37 to get pCi/L. That puts the 4.0 pCi/L action level at 148 Bq/m³, which EPA rounds to 150 Bq/m³ in its guidance. A monitor showing 200 Bq/m³, for example, works out to about 5.4 pCi/L.
What Do the Different Radon Levels Mean for My Home?
Here’s a quick way to read your number. It’s based on EPA guidance, which the North Carolina Radon Program at NCDHHS follows for homeowners.
| Result (pCi/L) | Approx. Bq/m³ | What it means | What to do |
|---|---|---|---|
| Below 2.0 | Below 74 | Below EPA’s “consider fixing” range. The U.S. indoor average is about 1.3 pCi/L. | No fix needed now. Test again in the future, after major renovations, or if you start living on a lower level. |
| 2.0 to 3.9 | 74 to 144 | Below the action level, but EPA notes no level of radon is known to be safe. | Consider mitigation. A long-term test will show your year-round average. |
| 4.0 to 7.9 | 148 to 292 | At or above the EPA action level of 4.0 pCi/L. | Confirm with a long-term or second short-term test, then fix the home if the result holds. |
| 8.0 or higher | 296 or higher | More than twice the EPA action level. | Take a second short-term test right away, then plan for mitigation. |
Keep in mind that a short-term result is a snapshot. Radon rises and falls from day to day and season to season, and it tends to run higher when homes are closed up in cooler months, a pattern we cover in our guide to the best time of year for radon testing in North Carolina.
Should I Retest Before Deciding on Radon Mitigation?
In most cases, yes. EPA’s guidance, which the NC Radon Program repeats, is to confirm a short-term result of 4 pCi/L or higher with a follow-up test before deciding to fix the home. You have two options:
- A long-term test (more than 90 days): This gives the best picture of your year-round average. If the long-term result is 4 pCi/L or higher, EPA recommends fixing the home.
- A second short-term test: This is the faster route when you need an answer soon. If the average of your first and second short-term tests is 4 pCi/L or higher, the guidance is to fix the home.
The higher your first number, the more sense a quick second short-term test makes. If your first short-term result is more than twice the action level, meaning above 8 pCi/L, EPA advises taking a second short-term test right away instead of waiting months for a long-term result.
Results close to the line are where follow-up testing earns its keep. EPA notes that if two short-term tests average 4.1 pCi/L, there’s about a 50% chance your year-round average is somewhat below 4. That’s not a reason to shrug it off, because levels just under 4 still fall in the “consider fixing” range, but it is a good reason to get a confirming measurement before you spend money. Our certified team can handle that confirming test through our residential radon testing service, which typically takes two days to a week depending on the type of test.
Could Something Have Thrown Off My Radon Test?
It’s worth checking before you retest. EPA’s instructions for a reliable short-term test include:
- Closing windows and outside doors at least 12 hours before a two- or three-day test and keeping them closed during the test, except for normal coming and going
- Placing the device in the lowest lived-in level of the home, in a room you use regularly (not the kitchen or bathroom), at least 20 inches off the floor and away from drafts, high heat, high humidity and exterior walls
- Running the test for at least 48 hours and avoiding short-term tests during unusually severe storms or high winds
If those conditions weren’t met, the result could be off. Keep in mind that open windows usually dilute radon, so a high number from a well-ventilated house is still worth taking seriously. And don’t dismiss a result because your home has no basement. NCDHHS recommends testing every home type, including crawlspace and slab homes, which is one of the common radon testing myths we hear most often.
How Worried Should I Be About a High Radon Level?
Concerned enough to act, but not alarmed. Radon is the second leading cause of lung cancer after smoking, and EPA estimates it’s linked to about 21,000 lung cancer deaths a year in the U.S. That risk comes from breathing elevated radon over many years, not from a few days or weeks in your home, and smoking adds substantially to it.
The encouraging part is that radon is very fixable. EPA says most homes can be brought down to 2 pCi/L or below with today’s methods, and NCDHHS notes that standard radon reduction systems are usually effective within 24 hours. You don’t need to move out. You need a plan.
It also helps to understand why our region tests high. Much of the Piedmont sits on uranium-bearing rock, and radon forms as that uranium breaks down. Our article on why North Carolina homes have high levels of radon gas explains the geology. Construction and ventilation matter too, so a neighbor’s result can’t tell you yours.
What Happens During a Radon Mitigation Visit?
If your follow-up test confirms radon at or above 4 pCi/L, or you decide to address a level in the 2 to 4 range, the next step is a mitigation system. Our residential radon mitigation process has three steps:
- Contact us: Schedule a free onsite consultation.
- Quote and schedule: A technician inspects your property and creates a custom system plan based on your foundation, layout and test results.
- System installation: We install the system and make sure it’s working properly.
Most systems use some form of soil suction. In homes with a slab or basement, that usually means sub-slab depressurization: a suction pipe goes through the slab, and a radon fan draws soil gas from beneath the house and vents it outdoors above the roof. The fan runs around the clock, and the system includes a warning device, usually a U-tube manometer, so you can see at a glance that it’s working.
Crawlspace homes, which are common across Central NC, need a different approach. EPA describes submembrane suction, where the crawlspace floor is covered with a heavy plastic sheet and a fan draws radon from beneath it, as the most effective method for crawlspace homes. If your crawlspace also has moisture, mold or pest problems, it’s worth asking about crawlspace encapsulation during the same consultation.
If you’re on a private well, there’s one more thing to consider. NCDHHS suggests that once high radon is found in the air, testing your well for radon in water can show whether your plumbing is adding to it. Radon in air is the bigger health concern, so the air system usually comes first.
How Do You Choose a Radon Mitigation Contractor?
If you’re comparing contractors, the NC Radon Program suggests asking whether they inspected your home in person, reviewed your test results, carry liability insurance, hold NRPP or NRSB certification, and guarantee to reduce radon below 4.0 pCi/L. Our team is recognized by the NRPP and IEA, and AmeriSafe is fully licensed and insured.
How Do I Know My Radon Mitigation System Is Working?
Testing again is the only way to know for sure. EPA and the NC Radon Program recommend a post-mitigation test no sooner than 24 hours after the system starts running and within 30 days of installation, with windows and doors closed for 12 hours before and during the test. A two- to seven-day measurement is recommended. We test again after installation to confirm your levels came down. EPA notes you can also hire an independent tester if you’d like a second check.
After that, a few simple habits keep the system doing its job:
- Glance at the manometer regularly. If the liquid levels in the U-tube are even, the fan may not be pulling suction.
- Never turn the fan off. It has to run continuously to work.
- Retest at least every two years, as EPA suggests, and again after major remodeling or if you start using a lower level of the home.
- Plan for a fan replacement down the road. Radon fans generally last 5 to 10 years, and our radon fan replacement and system repair service can usually swap one in a few hours.
We also recommend annual inspections. Our maintenance plan includes priority scheduling, an extended warranty, and 5% off both labor and parts.
What If My Radon Test Came Back High During a Home Sale?
EPA’s Home Buyer’s and Seller’s Guide to Radon allows short-term testing when results are needed quickly, using two passive tests taken at the same time or back to back, or a continuous monitor running for at least 48 hours, with steps to prevent tampering. If the average is 4 pCi/L or higher, EPA recommends fixing the home. NCDHHS also encourages sellers to address radon before listing, since it allows more time to find the most cost-effective solution. When you reach out, let us know it’s for a real estate transaction and share your estimated closing date so we can work around your timeline.
Ready to Talk Through Your Radon Results With a Local Expert?
You don’t have to sort out a high radon result on your own. AmeriSafe Water & Air is a locally owned radon, water and air company based at 4840 Sherrills Ford Rd in Salisbury. We serve homes within about 80 to 90 miles, including Charlotte, Greensboro, Winston-Salem, Concord, Mooresville, Statesville, Hickory and Gastonia. Share your numbers with us, and we’ll help you decide whether a follow-up test or a mitigation system is the right next step.
Call us at (704) 431-6231 or get a free quote to schedule a free onsite consultation.
