radon in basement 4

https://touch-wiki.win/index.php/How_a_Radon_Reduction_System_Protects_Your_Home_and_Health

If you have a basement, especially one that's rarely used or unfinished, radon could be building up down there without you knowing. This radioactive gas naturally seeps from the ground through cracks in the foundation, and it's a leading cause of lung cancer. The only way to know if your radon levels are safe is to test, which is cheap and easy to do. If levels are high, a simple mitigation system can vent the gas outside, making your basement safer to hang out in.