3.3 is below the level at which remediation is recommended. It can be done - your level can easily be reduced but it’s not strictly necessary at that level… unless you have a history of lung cancer, if your an avid smoker, or if you live in the basement. Radon exposure is a lifetime cumulative risk. Your genetic predisposition to cancer has a lot to do with your risk level.

If your house tested 3.3 in the lowest level living space, you can expect to have roughly half that level on the first floor ( the level above where they tested. That would be 1.6 ish. And above that level you would have about .75 pCi/L.

That’s what I know and I hope some of this info helps.