Abstract
The problem of residential radon has created a demand for testing services that has been partly met by industrial hygienists. The United States Environmental Protection Agency (EPA), while disavowing responsibility or jurisdiction in this matter, has nonetheless published guidelines for homeowners to use in interpreting test results. These guidelines are based on certain assumptions about the degree of equilibrium between radon gas and its daughters in typical dwellings under closed-house conditions. This paper presents data that indicate the EPA's assumptions are flawed and may lead to improper risk evaluation and unnecessary remedial action.