My only concern is with ACTIVE systems that are improperly installed, unless a passive would be set up so badly that it could cause a health risk. Photos on the page demonstrate improper and dangerous radon system installations.
Look at this picture. A piece of plastic placed over the sump pit and taped to the slab, then a Radon system installed off the pit. Really? This was done by a certified company, if you can believe that. This home is in Beaver Dam. We ended up replacing the whole system, but the fan.
Although I no longer install passive systems in existing homes (only new construction), I have installed a few where the vent pipe is routed out to ground level. These systems are set up so they could be made into active if needed some day. But, venting a sump pit or slab at ground level poses no health concerns because there would be almost no concentration coming out of the pipe.
Passive systems newly installed in existing homes just don’t work. For a few extra dollars you can rid the home of Radon, and hopefully reduce the moisture in the basement.
Radon is pushed up from ground pressures and sucked up from the vacuum of a home. If a pipe is routed to the sump pit or slab and vented to the outside, there is a chance that it might increase Radon levels. Why? Because if it’s windy outside and air is pushed into the vent pipe, more pressure can be exerted under the slab, thereby increasing the amount of Radon in the home.