Summertime short-term negative radon tests need to be retested in winter.

The Alabama Radon Program conducted a study to see if short-term radon tests performed during the summer air-conditioning season, and having results less than the U.S. Environmental Protection Agency (U.S. EPA) action level of 1.48x10(2) Bq m-3 (4.0 pCi L-1), were a reliable means in determining whether a house is in need of a radon removal system. Using a database of past Alabama Radon Program tests, individuals whose homes had tested less than the action level during the previous air-conditioning seasons of 2003, 2004, and 2005, were offered a free kit to conduct a wintertime retest. The study was done by mail, utilizing an initial contact letter, with participating homeowners being mailed liquid scintillation radon detection kits in January of 2006, performing the test, and mailing the completed test vial to the laboratory for analysis. There were 186 valid wintertime retests successfully completed statewide, with 27% having results greater than or equal to 1.48x10(2) Bq m-3. One hundred and six of those retests were in the known highest radon incidence areas of Alabama, where 41% tested at or above the U.S. EPA action level, some significantly higher. This study demonstrates that in the known high radon areas of Alabama there exists approximately a one-in-three chance that a house tested in the summertime and having a radon concentration of less than the action level will have a wintertime retest result equal to or greater than the action level.