radon mitigation before closing 4

https://radontestduringhomesource.valoradigest.com/posts/why-a-radon-test-during-home-inspection-matters-for-st.-louis-buyers

Before sealing up that crawlspace or basement, it's smart to get a radon mitigation system in place. A perforated pipe along the gravel layer draws soil gases away to a fan that vents above the roofline, so the house never draws in radon through the slab. Just make sure the sump hole is dug near the footing and the pipe runs straight up through an exterior wall—no sharp bends that could restrict flow. It adds a little prep time, but it saves suiting up for post-construction remediation later.