Radon level 91.5 pCi/L

I recently inspected a home that a young couple was buying. I recommended a few additional inspections; septic, radon and well. The septic came back fine, we are waiting on the results for the well, but of largest concern is a 91.5 PCI/L of radon. We all know that for PCI/L is acceptable but, this is 23 times that. Normally I would recommend radon remediation and simply referred them to a remediation specialists. But this is my son and my daughter-in-law! Now it really hits home!
I have a few questions: is it possible to remediate from this high-level down to an acceptable level? Is a wiser to walk away from this house? Can the basement be finished with these levels of radon? This house was built in the 1950s and I’m not certain of the basement floor construction. Is it necessary to have gravel under the concrete floor in order to install a radon system? Can a French drain system be integrated with a radon remediation system? Any input would be appreciated!

Charles, let me ask you first what area is this in?

OK next, please take no offense but how much experience do you have in Radon testing?
What type of testing do you use? a machine? Air Chek ? what?

That level is quite elevated, and I do quite a fair amount of Radon testing for several years.

I am thinking that before you go nuts, I would suggest a proper re-test myself as that level seems a bit nuts.


thanks for your response.

No offense taken! I am not certified to do radon testing. I paid for a radon class after trying to do the into InterNachi radon class. I got as far as the periodic table and I was done! I can handle the equipment but the science baffles me. Thereby, I am not getting my certification. I am very soon moving to Florida where there is an absolute miniscule amount of radon, so certification is not necessary.
I live in, and the house is in New Jersey. The testing person has been doing strictly radon tests for a decade, throughout the state of New Jersey. A secondary test is most likely a good idea! I would expect the sellers to demand that and/or perform that themselves.


OK Chuck, does the person that performed the test by any offer to do the radon mitigation system??? if so that is a no no in my book.

For a valid retest by someone you can trust have you considered asking a brotha NACHI member that services that area? We have many great guys here and I am sure that one would be willing to help a brotha out since it’s all in the family. I know if you were in my area I would do it free for you. OK well maybe a lunch…haha


Charles-To start with, please remain mindful that a radon mitigation system by itself does not necessarily remediate the situation.

For air (which contains radon) cannot enter the building without too elements: #1 there must be a whole (and there are plenty of them). #2 there must be a pressure differential across the whole for infiltration/exfiltration to occur.

The mitigation process should include the building performance as well as the design of the mitigation system. Basically weatherization issues are what cause elevated radon.

What affects radon levels is the intensity of the source, The distance from the source, the amount of dilution which occurs both in the soil and in the house before it gets to the testing device.

You can mitigate high levels of radon but all the bases should be covered. You ask about gravel below the concrete slab, this affects the ability of the radon mitigation system to draw air from great distances. If it’s not available a more expensive and extensive radon system would be required.

Using a French drain (I don’t know if you mean a drain installed on the interior or the one installed on the exterior) to depressurize the exterior of the foundation is a method but the drain must be located on the exterior because you don’t want to be pulling radon through the foundation to the interior when your goal is to keep it on the exterior.

A second test is not just a good idea, it’s required before you get started (if you’re working with me)!

Finishing a basement in the future is going to change everything and radon testing should be part of that process as well. I would be highly skeptical in finishing off a basement and a house built in the 50s with this radon level. The house was not initially constructed for the basement to be finished and it is problematic before you even get started. (And not just about the radon problem).

Thanks Dave, that saved all kinds of typing.

The above statement from Dave is WELL worth repeating. Heck it is worth memorizing…:cool:


Thanks a lot guys!! It’s so nice having a pool of experience that can be tapped in an organization, such as this. AND it is only as good as the members that will contribute!!
If you have more thoughts or anyone else want to jump in, please feel free!!

Sorry for the typo’s, I’m voice texting on the road to Owensboro, KY…

Testing the water levels in the Ohio River! :-0

Answered in order asked.

Done all the time. Radon levels in the thousands are mitigated to <4pCi/L.

Not enough info to answer:

Gravel sure helps. Wet mud sure doesn’t.

Yes, if you are referring to an interior french drain. The french drain might actually be a major contributing factor to the high radon levels.

@ David- No prob with the typos- I do not type, I peck with one finger. So, to sdo extensive reports I use “Dragon Speak” dictation software. Even typos there. Thanks very much for your help!!
Nick and everyone else. We are getting it tested again. The first Radon guy (he only tests, not mitigate- which is why I use him), He is giving us a break on the second test. We are worried about the Seller messing with the test, if they do it. But, we never heard of that happening, eh? We are also getting a mitigation company- recommended by the State Radon Office.
Thanks again-all
I am a NJ Certified Tree Expert, if I can help anyone with Horticultural questions, I am happy to help. (Northern Plants) I actually offer a “Landscape Vitality Inspection” as part of my Menu offerings.

I’ve done several in the mid to high 80’s in Kansas City. Mitigation has lowered them to acceptable levels. When I’ve done one of these, I offer a retest at no cost to clients AND always use 2 separate electronic monitors for the retest (not the original monitor).

Its logical most sellers would want their own guy testing also, hoping you were off

whether it’s done for free or not, retesting should always be performed as prescribed by the EPA protocol!

In reality, one high reading is all it seems to take to get a radon mitigation system installed around here, without any other consideration.

91.5 pCi/liter…
is a low level…
In some areas here…
200, 300, 400, 500, 600 etc are the norm…

a PicoCurie is parts per Trillion of a Curie…
the difference between a 4 and 8 is not that great…