[CydeWeys]

It rises up out of the ground, and the (expensive) solution is to install a vacuum system beneath the slab that vents the the outside. I know because my parents' house has such a system. More info: https://sosradon.org/reducing-radon-in-your-home

You can tell it's working because there's a U-shaped pressure gauge attached to the system showing the differential between under the slab and outside: https://www.clutchprep.com/physics/gauge-u-shaped-tube