Beware summer radon-test results

Measuring radon with testing kits that sit in a house for just a few days can yield misleadingly low values in summer, a new study finds.

Alabama maintains a statewide database of 36,000 domestic measurements of radon, a radioactive gas emitted by rocks in soil. Although these data revealed some geographical hot spots, radon readings in such areas were often unexpectedly low if testing had occurred in summer.