The good news about radon is that finding out your level is easy. You can test a house yourself for little or no money, or hire a professional to do it. Neither one is "the real test" and the other a toy. They answer slightly different needs.
Here is how the options compare and when each one makes the most sense for an Upstate home.
The basics that apply to every test
Whoever does the testing, the EPA's ground rules are the same:
- Test the lowest lived-in level of the home. That is a basement if you use it, otherwise the main floor. In a crawl space home, that means the main floor, not the crawl space.
- Short-term tests run 2 to 90 days. They are a snapshot.
- Long-term tests run more than 90 days and give a better picture of your year-round average.
- Closed-house conditions: for short-term tests, keep windows and exterior doors closed for 12 hours before and during the test, apart from normal coming and going.
- The action level is 4 pCi/L. The EPA recommends fixing a home at or above 4 and considering it between 2 and 4.
Option 1: South Carolina's free test kit
The South Carolina Department of Environmental Services (SCDES) offers one free radon test kit per home, while supplies last. You can request one through the radon page at des.sc.gov/radon.
It is a genuinely good program, but there is a catch that has nothing to do with the kit. According to a 2022 SC Public Radio report, the state sends out about 1,600 free kits a year, and only about 40% come back to the lab. A kit sitting in a drawer tells you nothing. If you order one, put it out when it arrives and mail it back on time.
Best for: a first look at your home's level when you are not on a deadline.
Option 2: A store-bought test kit
Hardware stores and online retailers sell short-term and long-term radon kits, typically in the range of about $15 to $50, often with the lab fee included. You set the kit out, leave it for the stated time, seal it and mail it to the lab.
What goes right: cheap, easy and good enough to tell you whether you have a problem.
What goes wrong: most bad DIY results come from setup, not the kit.
- Placing it in the wrong spot, like a kitchen, bathroom, crawl space or next to a window
- Leaving windows open or running a whole-house fan during the test
- Letting the kit sit too long before mailing, so it misses the lab's window
- Not recording start and stop times correctly
Best for: homeowners checking their own home, retesting periodically or doing a long-term follow-up.
Option 3: A continuous radon monitor
Continuous monitors are electronic devices that measure radon over time and show results as they go, rather than sending a sample to a lab. Consumer models are sold for homeowners, and professional-grade monitors are what testing pros typically use.
Their big advantage is that you can see how levels rise and fall over hours and days, which helps explain why one short-term test might differ from another. A consumer monitor is a nice way to keep an eye on things over the long run. In a real estate deal, though, the other side will usually expect a professional test with documented setup.
Option 4: A professional radon test
A professional test usually uses a continuous monitor, placed and documented by the tester, with a written report at the end. A professional short-term test typically starts from about $150.
What you are paying for is less about the device and more about the process:
- Correct placement on the lowest lived-in level
- Instructions for closed-house conditions, and a check that they were followed
- Hour-by-hour data rather than a single number
- A dated report that a buyer, seller or agent can rely on
See our radon testing page for how we handle it.
When a professional test really matters
Real estate transactions
When a home is being bought or sold, two parties with opposite interests need to trust the number. A professional test with documented setup is the standard choice. Inspection windows are short, so the test needs to be scheduled quickly and done right the first time. Our guide to radon when buying or selling in SC covers this in detail, and our home sale radon mitigation page explains how we work to a closing date.
Confirming a mitigation system works
The EPA recommends retesting after a radon system is installed. We run a post-install test on every system we put in, so you can see the before and after for yourself.
Borderline or confusing results
If your DIY tests are bouncing between 3 and 5, or one test says high and another says low, a continuous monitor can show what is happening. Our post on radon between 2 and 4 pCi/L walks through that decision.
You need an answer fast
If you have a deadline, a professional test removes the lab mailing time and the risk of a kit getting lost or arriving late.
Quick comparison
| Option | Cost | Best for |
|---|---|---|
| SCDES free kit | Free, one per home while supplies last | A first look, no deadline |
| Store-bought kit | Typically about $15–$50 | Homeowner checks and long-term tests |
| Consumer continuous monitor | Varies by model | Ongoing monitoring at home |
| Professional short-term test | From about $150 (typical range) | Real estate, post-mitigation checks, borderline results |
Already tested and got a high number? You do not need to start over. If a DIY test came back at 4 pCi/L or higher, we can look at your foundation and give you a written estimate. Get a free quote.
Our honest recommendation
For most Upstate homeowners who simply want to know, start with a DIY kit or the free state kit, done carefully. If the result is low, retest periodically and after major changes to the house. If it is 4 or higher, or you are buying or selling, a professional test and a mitigation estimate are the next step.
Radon is common enough in the Upstate that testing is worth doing in every home. Greenville County is the state's only EPA Radon Zone 1 county, and Oconee County has the highest average of the five Upstate counties at 5.0 pCi/L. See our Upstate radon data for the rest, and our radon mitigation cost guide if your number comes back high.
Frequently asked questions
Can I test for radon myself?
Yes. A DIY kit, or South Carolina's free kit from SCDES, gives a useful result if you follow the instructions: test the lowest lived-in level, keep windows and exterior doors closed for 12 hours before and during a short-term test, and mail it promptly. For real estate deals or post-mitigation checks, a professional test is usually the better choice.
How much does a professional radon test cost?
A professional short-term radon test typically starts from about $150. That covers correct placement, a continuous monitor that records levels over time and a dated written report. Store-bought kits typically run about $15 to $50, and South Carolina offers one free kit per home while supplies last. The final price depends on the home and timing.