sub-slab depressurization

https://radontestresults.brightpathdigest.com/posts/understanding-your-radon-test-results-what-they-mean-for-your-home

Sub-slab depressurization is a remediation technique where a network of pipes is installed beneath a concrete floor slab to create a vacuum that pulls soil gases like radon or vapors from contaminated soil away from the building, venting them safely above the roof.