average radon level in house
A half of American homes have a radon level above 0.67 pCi/L (the median level). The average (mean) radon level in US homes is 1.25 pCi/L, or three times higher than the average level outdoors. Nearly 8 million US homes, or 1 out of every 15, have radon levels above the EPA's 4 pCi/L action limit and nearly 1 out of 6 exceed the EPA's 2 pCi/L consider action limit.