radon vent pipe

https://radonfaninstallationhaven.alderbrief.com/posts/getting-radon-fan-installation-right-what-homeowners-should-know

The radon vent pipe sticks out of the ground like a small chimney, quietly pulling dangerous gas from beneath your home and releasing it safely into the air above. It's a simple but critical pipe in a mitigation system, often made of white PVC, running from the sub-slab or crawl space up past the roofline. Without it, that invisible radioactive gas could build up inside your living spaces.