sub-slab depressurization

https://theradonhomesaleinsight.greyhavendaily.com/posts/what-sellers-need-to-know-about-radon-home-sale-testing

Sub-slab depressurization is a radon mitigation technique where a pipe is inserted through the concrete floor slab into the soil or gravel beneath. A fan creates negative pressure under the slab, pulling radon gas away from the building and venting it safely outside. It's a quiet, effective system that often goes unnoticed once installed, providing peace of mind without intrusive equipment inside the living space.