Testing for Radon
Test for radon in places where people spend a lot of time: homes, childcare centers, schools, and workplaces. You can’t see or smell radon, so testing is the only way to know if you are being exposed to high levels.
Radon test kits are inexpensive, accurate, and widely available. You can buy a test kit for $10-$30 online, at your local hardware store, or through your regional Radon Information Center.
We recommend starting with your regional Radon Information Center since many centers provide test kits for free or reduced cost, and often with laboratory fees covered. Additionally, Radon Information Center staff are professionally trained in radon measurement and can help answer all your radon questions.
You can test for radon on your own with a test kit, or hire a contractor to test. Hiring a contractor is more expensive but can be useful, especially when testing large buildings like schools or commercial child care centers, multifamily apartment complexes, and workplaces. Hiring a radon measurement specialist may also be useful during real estate transactions.
Types of radon tests
Short-term: Measures radon levels for two to four days and is a quick way to screen your home for radon. Start with a short-term test.
Long-term: Measures radon levels for a minimum of 91 days (typically 6-12 months). They are the best way to estimate the annual average of radon in the home. Long-term testing should include both heating and non-heating seasons.
Before you test
- Read the instructions that come with the radon test kit
- Close exterior doors and windows for at least 12 hours before starting the test. You can still enter and exit your home as normal.
Starting your test
- Remove your charcoal radon test from the plastic bag—this begins your test!
- Fill out the form that comes with your kit—be sure to record your start date and time.
- Place the test on the lowest level of your home where you spend at least seven hours a week. For real estate transactions, test the lowest level of the home, such as the basement.
- Do not place the test in areas with high humidity (bathrooms, kitchens, or crawlspace), or in direct sunlight.
- Place the test 2 to 7 feet above the floor, on a table or surface that is at least 3 feet from an exterior door, window, or air vents.
- Place the test with the paper side facing upwards, on a flat surface.
- Make a reminder to yourself to end your test at the appropriate time. Refer to your test kit's instructions, but typically 48 - 96 hours.
Stopping your test
- Stop your test within the appropriate time period. Test kits exposed for too long or for not enough time are invalid.
- Fill out the remaining portions of your form—be sure to record your end date and time.
- Seal up the radon test with the form (if the test you purchased requires lab fees, be sure to include those funds).
- Mail the package as soon as possible. Most labs must receive the kit within 10 days of stopping the test (including shipping time).
If you have never done a radon test in your home or building, now is the time.
Plan to test every two to five years in case levels of radon in your home change. Test when buying a home or after any major renovation that affects the home’s foundation, heating or cooling, or after completion of any weatherization projects, such as replacing windows and doors.
Considering seasons
You can test for radon at any time of the year, but winter is an especially a good time to test. During the winter season, it's easier to maintain "closed building conditions," which means that windows and doors are kept closed.
For a short-term test, close doors and windows for at least 12 hours before starting the test. You can still enter and exit your home as normal. Run the heating and air conditioning system as normal too. For a long-term test, plan for a time when you can have closed building conditions for at least half of the time. For example, if your long-term test requires 90 days, test when at least 45 days are with closed building conditions.
Considering weather
Weather can also affect the radon levels in the home. If there is severe or unusually windy weather, wait to perform a short-term test.
Yes. Radon can be high in any type of home or building, old or new.
Radon levels depend on where your home is located in relation to a uranium deposit in the soil. You could have high radon levels even if your neighbor’s radon level is low. Testing is the only way to know.
The risk of radon exposure through your home's water is much lower compared to the risk of exposure in the air.
If you are concerned about radon in water, you can find more information on the Wisconsin Department of Natural Resources
Understanding your radon test results
There are two basic types of radon tests: Short-Term and long-term. The EPA recommends first doing a short-term test (two to four days). If your test result comes back at 4 picocuries per liter (pCi/L) or higher, do a second test (either long-term or short-term).
A long-term test can help provide a better estimate of your home's annual radon concentration. Long-term tests take at least 91 days, can be placed for up to 365 days (one year).
If your first test result is above 8 pCi/L, use a short-term test for your second test. A second test is needed to confirm the results of your first test. The following table explains steps to take.
| Test result | Steps needed |
|---|---|
| Less than 4 pCi/L | Your home has low radon levels. You do not need mitigation. Re-test every 2-5 years in case levels of radon in your home change. Test after any major renovation that affects the home's foundation, heating or cooling, or after completion of any weatherization projects such as replacing windows and doors. |
| Between 4-7 pCi/L | Do a second radon test. A long-term test kit will help you understand your average annual radon exposure. You can instead use a short-term test if you need a quicker result. If the average of the two results is greater than 4 pCi/L, we recommend mitigating. Note: Radon levels can change with seasons. Radon levels are lower when windows are open and there is greater ventilation. Long-term testing should include both heating and non-heating seasons. |
| 8 pCi/L and above | Do a second short-term radon test immediately. If the average of the two results is greater than 4 pCi/L, we recommend hiring a certified contractor to mitigate your home. |
Radon is measured in picocuries per
Questions?
Experts are available statewide to answer your questions and provide test kits to the general public. Get in touch with a radon expert by contacting your regional Radon Information Center or by calling 1-888-LOW-RADON (1-888-569-7236).