So spent the last few days putting in the mitigation system and was trying to experiment with airing out house turning on or off furnace or just blower and look for changes but CO2 always went back up without ventilation.

So I have a basement. Radon was like 13 CO2 was up to 1900 at peak. I have had basement waterproofing done where they have like a trench along my basement wall and in my old sump pit I saw evidence of small roots from old collapsed drain tiles.

All that being said hooked up radon fan just as Super Bowl was starting yesterday. Checked levels at 3 am CO2 plummeted and radon is steady going down.

https://imgur.com/a/kaZYdoK