Predicting the annual concentration of indoor 222Rn from one or more short-term measurements.

Long-term and short-term measurements of indoor 222Rn from 480 houses located in eleven states were used to study the relationship between the annual living area average (ALAA) and 1) a single 2 d measurement and 2) the mean of multiple 2 d measurements (taken in different seasons). Of particular interest is the issue of using a short-term measurement(s) to predict the ALAA in a given house. The results indicate that with 95% confidence (approximately): 1) a single 2 d measurement gives an interval estimate of the true ALAA that is within a factor of 2.5 of the predicted ALAA; and 2) a mean of two 2 d measurements (taken in different seasons) gives an interval estimate that is within a factor of 2.2 of the predicted ALAA. If a more precise estimate of the ALAA is needed, then an alternative procedure to using 2 d measurements should be employed (e.g., measure the annual concentration directly).