Uncertainty and the Johnson-Ettinger Model for Vapor Intrusion Calculations
The Johnson-Ettinger Model is widely used for assessing the impacts of contaminated vapors on residential air quality. Typical use of this model relies on a suite of estimated data, with few site-specific measurements. Software was developed to provide the public with automated uncertainty analysis applied to the model. (See http://www.epa.gov/athens/onsite.) An uncertainty analysis was performed on the model, that accounted for synergistic effects among variable model parameters. This analysis showed that a simple “one-at-a time” parameter uncertainty analysis provides a rough guide for the uncertainty generated by individual parameters and allowed their ranking.