In my part of the country we have a lot of rock formations close to the surface of the earth which creates a haven for Radon gas.
For those of you that may not have had any direct experience or heard much about it; Radon is a colorless, odorless, gas that occurs during the natural breakdown of uranium which is in most all of the United States.
According to the Environmental Protection Agency (EPA), Radon is the second leading cause of lung cancer in the US ranking just behind smoking as a killer.
Here's a link to the EPA website where you can learn more than you ever intended to know about Radon gas.
Again based on EPA data the safest level of Radon in a home that does not require mitigation is 4 Picocuries per Liter of air or less, commonly written as pCi/L. I have no idea how much a Picocurie is but I'm guessing it's not much.
In selling homes in some areas of the country Radon testing is more common than others. If you live in someplace like Florida or a western state that has porus, sandy soil you usually don't have much in the way of Radon concentrations but it's still there.
There seems to be no rhyme or reason as to areas of a town or county that have higher or lower Radon levels; it's just either there or it's not.
If you have a listing or a buyer that gets a Radon test and finds level above the magic 4 pCi/L they probably need to have it mitigated.
There are several methods to fix high Radon levels and none of them are very expensive.
One of the most common mitigation systems involves digging a dry sump (hole in the ground) in the lowest point of a basement or crawl space and installing a vent van to keep the Radon laces air in the sump pumped out of the house into the atmosphere. Into the atmosphere is where the Radon would go anyway if the house were not trapping it.
Radon is not dangerous when diluted into the atmosphere and is generally only a concern when local concentrations get too high in your basements or crawl spaces.
I've had to deal with too high Radon levels twice in my real estate career.
The first time we installed the dry sump with an always on fan running and a 4 inch PVC pipe venting to outside the basement to carry away the Radon. I believe the cost to do that was around $2500 which is a little on the high side for mitigation but they had to run the pipe a long way from the basement to outside.
The second time was with a crawlspace house where the seller had planted nice, thick Holly bushes all around his foundation perimeter. I believe the Radon concentration inside that house was around 5 or 6 pCi/L.
I took my hedge clippers over and cut back the Holly bushes to let air circulate through the foundation vents and on the second Radon test a week later the levels had dropped to just over 1 pCi/L.
So if you have a listing or a buyer and find Radon gas during a test, don't panic; it's usually a fairly quick & easy fix for minimum costs.