Effect of Ambient Air Quality on Soil Vapor and Indoor Air Quality

摘要

Over the past several years, vapor intrusion (VI) has emerged as a significant risk pathway for volatile organic compounds (VOCs). As it has become recognized as a significant contaminant migration pathway, various technical guidance documents have been developed. Review of these documents reveals a generally consistent approach to evaluating VI – the lines of evidence approach. This approach involves collection of soil gas (typically sub-slab soil vapor), indoor air, and ambient outdoor air samples. The objective of this approach is to establish whether there is a concentration gradient from soil vapor to indoor air, suggesting that VOCs detected in indoor air are likely attributable to a subsurface source. However, in some cases, the concentration gradient is reversed, suggesting that VOCs present inside the structure (e.g., building materials, household/office chemicals, dry cleaned clothing, furniture, carpeting, etc.) may be the source of VOCs detected in indoor air samples. A third potential source of VOCs in indoor air is the presence of VOCs in outdoor ambient air.