sub-slab depressurization 4

https://radonsystemwarrantysource.dovetailscope.com/posts/what-a-radon-system-warranty-covers-and-what-it-doesn-t

Sub-slab depressurization is a method used to prevent soil gases like radon from entering buildings by creating a vacuum beneath the concrete floor slab. A fan system pulls air from under the slab and vents it safely above the roofline, which lowers the pressure so gases don't seep through cracks. It's a common fix in homes with high radon levels, often paired with sealing gaps in the foundation for better effectiveness.