“Radon Fountains” spray radon-rich soil gas into the living space breathing zones.
This slab penetration leaves a direct opening from above the slab down and into the soil. There is no evidence that the installer made any effort to seal this opening to block entry of radon-rich soil gas through this port. Result? a potential “Radon Fountain” into the area above the unsealed penetration.
There may be many other unsealed penetrations that pass through holes in the membrane beneath the poured slab.