What is radon?
Written and reviewed by Bill Dahlstrom, Illinois radon mitigation license RNM2018212 · Updated
Radon is a gas that comes up out of the ground and into homes. The only way to know your level is to test. Cook County mails a free kit to homes in suburban Cook County, and Will County sells one for $8. If your number is high, it can be fixed.
Where radon comes from
Radon forms when soil and rock break down naturally. The U.S. EPA calls it a radioactive gas. It collects most in the lower rooms of a home.
How do I test my home?
Set the test in the right spot
Put it in the lowest level of the home you use or could live in, and test each one if there is more than one. Follow the instructions that came with the test and the Illinois placement rules.
Read the number
Your result is a number in pCi/L, the standard unit for radon in air. The next section says what it means.
What does 4.0 pCi/L mean?
pCi/L stands for picocuries per liter. The EPA recommends fixing your home if your radon is 4.0 pCi/L or higher.
A number over 4.0 doesn't mean you need to panic or stop using your home. It means it's time to find out what a system would take in your home.
Why test before you sell?
A lot of people first hear about radon when they sell their home. If you test now and it's low, you can stop thinking about it. If it's high, you can fix it while you still live there, instead of when a buyer's test makes you.
What happens if my level is high?
Before we price anything, Bill comes out and looks at the foundation, the sump, any finished rooms or crawl space, and where the pipe can go outside. Then he tells you where the pipe and fan would go and what install day looks like.
What the system is doing
Radon is measurable and fixable. These two views show why testing matters and why a mitigation system is designed around the whole home, not just one visible crack.
Pressure under the home finds small openings
Radon usually is not coming from one single hole. Pressure under the home lets soil gas move upward through porous concrete itself, sump openings, crawl spaces, cracks, and small gaps around pipes.
The fan creates the easier path out
A mitigation fan creates a lower-pressure path under the home, so radon is pulled into the pipe before it enters the living space, then vented above the roofline.
Got your result?
If it's 4.0 or higher, call Bill or fill in your info for a quote. Still need a test? Our testing guide shows where to get one.
Helpful official radon resources
Last reviewed by American Radon Systems: June 2026
- U.S. EPA radon overview
Plain-language federal guidance on what radon is and why testing matters.
- CDC radon overview
Public-health guidance on radon exposure, testing, and reducing levels in homes.
- Illinois IEMA-OHS Radon Program
The state radon program for Illinois homeowners and radon professionals.
- American Lung Association radon resource
Nonprofit indoor-air guidance on radon and lung health.
Common questions about radon
Short answers based on EPA and CDC guidance.
What is radon?
Radon is a naturally occurring radioactive gas that comes from soil and rock under the home. You cannot see it or smell it. The only practical way to know the level in a specific home is to test.
How does radon get into a house?
Pressure under the home can pull soil gas up through porous concrete, sump openings, crawl spaces, cracks, seams, and small gaps around pipes. It is usually not one single hole. That is why systems are designed around the whole foundation, not just a visible crack.
What is the EPA action level for radon?
The U.S. EPA action level is 4.0 pCi/L. At or above that, EPA recommends fixing the home. EPA also suggests considering action between 2.0 and 4.0 pCi/L. For scale, EPA puts the average indoor level in the United States at about 1.3 pCi/L and outdoor air at about 0.4 pCi/L; there is no safe level, only lower and higher. American Radon Systems follows that guidance without scare tactics. Your own test result is the number that matters for your home.
Can you smell or see radon?
No. Radon has no color, smell, or taste. A home can feel completely normal and still have an elevated result. That is why testing is the only way to know.
Can my neighbor’s test tell me about my home?
No. Levels can differ house to house, even next door, because soil, foundations, and air pressure differ. A neighbor’s high or low result is a reason to test your own home, not a substitute for your number.
Can a newer home still have high radon?
Yes. Radon comes from the soil, not the age of the house. Newer Illinois homes often have passive radon piping by law, but that pipe does not always keep the level down until a fan is added when testing shows it is needed.
Is radon fixable?
Yes. Elevated radon is a common, fixable home issue. A properly designed mitigation system creates a lower-pressure path under the home so soil gas is pulled into a pipe and vented outside. Most installs are finished in one visit after Bill has looked at the home.
What is a radon mitigation system and how does it work?
Most homes use sub-slab depressurization: a fan and pipe pull soil gas from under the foundation and vent it outside above the roofline. A U-tube manometer on the pipe shows the fan is creating suction. The exact layout depends on basements, crawl spaces, slabs, sumps, and finished spaces. Bill designs for the home you have, not a one-size layout.
Is radon actually dangerous?
Yes, over time. EPA identifies radon as the second leading cause of lung cancer in the United States and the number one cause among people who have never smoked. EPA estimates about 21,000 lung cancer deaths a year are related to radon, and the risk is higher for smokers. There are no short-term symptoms, which is why testing, not how you feel, is the only way to know your level. EPA recommends fixing a home at 4 pCi/L or higher.