radon vent pipe

https://radonretestverificationmarket.nexorafield.com/posts/why-radon-retest-verification-matters-for-west-st.-louis-county-homeowners

A radon vent pipe sticks out from the side or roof of a house, usually a white PVC pipe capped with a gooseneck or mushroom top. It's part of a system that pulls radon gas from beneath the foundation and releases it safely outside, preventing radioactive buildup that can cause lung cancer. The pipe needs to stay clear of snow and debris to work right.