Examination of the U.S. EPA's vapor intrusion database based on models.

In the United States Environmental Protection Agency (U.S. EPA)'s vapor intrusion (VI) database, there appears to be a trend showing an inverse relationship between the indoor air concentration attenuation factor and the subsurface source vapor concentration. This is inconsistent with the physical understanding in current vapor intrusion models. This article explores possible reasons for this apparent discrepancy. Soil vapor transport processes occur independently of the actual building entry process and are consistent with the trends in the database results. A recent EPA technical report provided a list of factors affecting vapor intrusion, and the influence of some of these are explored in the context of the database results.