I am trying to think of a way of installing a stealthy sub-slab radon venting system. The pipe chase on my house appears to have room for another vent pipe (I have oil and wood stove chimneys in there now). Could I run a plastic pipe in that chase? If it doesn't get any closer than the wood in there, shouldn't it be safe, or would I have to use a metal pipe (the air is said to be humid, esp. in winter, so I'm not sure if rusting would be a concern). Would I need a metal vent above the chase's top? It seems like a good way to go because since it is enclosed all the way the humid air may not condense and freeze like it can do on an ugly outside installation. I really don't want to do a roof penetration on the metal roof, and also routing through the interior would be a problem. There is also a possibility that the passive approach will work and I won't have to add a fan. Thanks for any ideas. I'm getting more pressure to do something about this, although the numbers don't concern me that much (currently 2.3 upstairs and ~6 downstairs (with window closed and dehumidifier running)), but I think it got up to 12 at one point in the basement. Interestingly, I believe the furnace operation in winter sucks some of the zoomies out through the stack. Note: Since I have the radon monitors I will be putting the fan in the basement where it can easily be accessed. I understand that EPA has written they prefer a system where the piping inside the house under vacuum in case of links, but that was before these new-fangled detectors. In EPA's guidelines it seems the only place they like to have the fan is in the attic (noise, accessability) or outside (ugly, maintenance, freeze ups).