Hello Jerry Cohen, Find here, your "answer of enlightenment": http://www.epa.gov/aging/press/epanews/2011/2011_0620_2.htm Frightens the he** out of me! Patricia Lewis Free Enterprise Radon Health Mine PO Box 67 Boulder MT 59632 406 225-3383 (ofc) 888 890-5860 (ofc toll free) http://www.radonmine.com *"fan" us on Facebook !*