How much radon is dangerous if I’m going to live in the basement of a house?

The EPA action level is 4.0 pCi/L. At or above that number, the EPA says fix it. Between 2.0 and 4.0, the EPA says consider fixing it. If you plan to sleep and spend hours every day in a basement, those numbers matter even more, because radon pools low and you will breathe it the longest.

Radon is a radioactive gas you cannot see or smell. It seeps up out of the soil and rock under your house. New Hampshire sits on a lot of granite, and granite gives off radon. So this is a normal thing to test for here.

Here is the part that matters for you. Radon is heaviest down low. The basement is usually the highest-reading room in the whole house. A reading that looks mild upstairs can be a lot worse on the floor where you want to live. That is why the basement is the right place to test, not the kitchen.

So how much is dangerous? There is no level the EPA calls perfectly safe. Outdoor air runs around 0.4 pCi/L for reference. The EPA draws the action line at 4.0 pCi/L and asks you to think hard about fixing anything over 2.0. For a room you live in full time, treating 2.0 to 4.0 as a real concern is the careful move. Above 4.0, you should plan to fix it.

You start with a test. That is the only way to know your number. A short term test sits in the basement for a few days. A long term test reads for months and gives you a truer year round average, since radon swings with the seasons and the weather. We can run a radon test for $50, credited toward the job if you move ahead if you want us to handle it. You can also buy a kit yourself. Either way, test the basement, since that is where you will be.

If the number comes back high, the fix is a mitigation system. For a normal poured or block basement, that means active sub slab depressurization. A pipe goes through the slab, a fan runs on it, and the fan pulls the radon out from under the floor and vents it up above the roofline before it ever gets into your air. For a dirt or fieldstone crawl, we do a sub membrane version instead, sealing the floor and pulling from under the membrane. A radon mitigation system runs $900 to $6,000, and most homes land around $1,950 to $2,250. We install both kinds.

You do not need a giant project to deal with radon. Mitigation is a focused job, not a basement gut. If your only issue is radon, you do not need waterproofing or finishing thrown in. Test first. Fix what the number tells you to fix.

One thing worth knowing if you are about to live down there. Radon and water often show up in the same basement, because the same cracks and the same floor wall joint that let water seep also let gas seep. A damp basement is also harder to keep healthy to live in. If you find both, we can talk about both. If you only have radon, we only fix radon.

Our radon work carries a 10 year warranty on the system. We do not guarantee a specific radon level unless that promise is in writing. After we install, retesting is your call as the homeowner to confirm the result over time.

Branden runs radon for us. We call him B-Radon. He is OSHA certified and our shop holds the state radon cert RMS-113966, so this is licensed work. We are licensed and insured, BBB A+ accredited, and trusted by 5,000+ homeowners across New England.

Want to read more about the system itself? See our radon mitigation page. If your basement is also damp, our basement waterproofing page covers the Forever Dry System, and crawl space services covers encapsulation for a dirt floor crawl. Every job is backed by the 603 guarantee.

For the science and the numbers, lean on neutral authorities. The EPA radon program sets the 4.0 pCi/L action level and the 2.0 to 4.0 consider range. NH DHHS radon [verify] has guidance specific to our state. Those are the sources to trust on health thresholds, not a contractor.

Ready to test your basement before you move in?

Call us at 603-610-1770 or book your free inspection. We will give you a number you can act on, and a free estimate within 24 hours. Test it, then live in it!

Related questions

Should I test for radon before I finish a basement to live in? Yes. Test before you spend a dime on finishing. If the number is high, you fix radon first, then finish. Finishing over a radon problem just traps you in the room with it.

What does a radon mitigation system cost? A radon mitigation system runs $900 to $6,000, and most homes land around $1,950 to $2,250, and a radon test runs $50, credited toward the job if you move ahead. The exact figure depends on your foundation, your layout, and where the pipe and fan have to go. We give a free estimate within 24 hours.

Will a radon system make my basement noisy or ugly? No. The fan is quiet and usually sits outside or in a utility area, with a single pipe running up and out. Most homeowners forget it is there once it is running.

Does radon come back after you fix it? A working system keeps pulling gas out from under the slab as long as the fan runs. Our radon mitigation carries a 10 year warranty on the system. Retesting over time is the homeowner’s job to confirm the level stays where you want it.