Predicted fraction of homes exceeding the EPA's recommended action level
of 4 pCi/L
Important: high-radon homes tend to cluster within counties. Even
if your county has only a low percentage of high-radon homes, you could
still be in a high-radon "pocket." If you have reason to suspect
that that might be the case---for example, if one or more of your neighbors
has tested their home and has a high radon concentration---then you might
want to test, even if your county is generally not at risk.
Also, there are other risk factors. One result of the LBNL high-radon
project has been a better understanding of what causes variation from one
house to the next and one area to the next. Click
here to see some research results about that.
Recall that this map shows the estimated fraction of homes with long-term,
living-area average concentrations over 4 pCi/L. Most people
perform short-term monitoring on the lowest level of the home, which yields
a biased (and highly variable) estimate of the living-area average over
the course of the year. Make a long-term measurement if you have
the time!
Colors may be hard to distinguish, particularly among the greens.
Click here for a grayscale map that might be easier to read.