Sub-slab depressurization is a common technique used in homes with crawlspaces or basements to prevent soil gas—like radon or moisture—from seeping indoors. A fan creates negative pressure beneath the concrete slab, drawing harmful vapors away from the foundation and venting them safely outside. It's often the go-to fix for radon problems because it's reliable and relatively unobtrusive once installed. If you're dealing with musty smells or high radon readings, this system can make a real diffe… sub-slab depressurization 7