Alternate Performance Standard Project - Interpreting the Post - Construction Test

In support of a possible performance standard for radon-resistant construction for the State of Florida, a protocol is needed to provide postconstruction indoor radon measurement. In order to relate the results of short term compliance measurements to inferred annual average concentrations, a study was conducted in four regions of Florida known to have potential for elevated indoor radon. Eighty study homes in Polk, Alachua, Dade, and Leon counties are being simultaneously monitored using long term (quarterly and annual alpha track and long term electret-ion chambers) and short term monitors (open-face and barrier charcoal canister and short term electret-ion chambers). Electrets are deployed continuously and read over oneand twoweek intervals. A subset of the houses are monitored using Pylon AB-5 continuous radon monitors. Houses were selected to be representative of typical Florida housing construction, with indoor radon concentration in the 2-20 pCi/L range. Data have been analyzed to isolate systematic seasonal variations and to derive confidence limits for predicted long term (annual) averages from short term measurements according to the candidate protocols. For relevant combinations of device and sampling period, thresholds have been determined below which a single short-term measurement can provide specified confidence that the long-term average radon does not exceed 4 pCi/L. These results have been incorporated into draft building standards.