How is soil vapor intrusion investigated at sites contaminated with volatile chemicals?
The process of investigating soil vapor intrusion typically requires more than one set of samples to determine the extent of vapor contamination. Several different types of environmental samples may be collected: soil vapor samples, sub-slab vapor samples, samples from the air found in crawl spaces, indoor air samples, and outdoor air (sometimes referred to as “ambient air”) samples. Soil vapor samples are collected to characterize the nature and extent of vapor contamination in the soil in a given area. They may be collected before sub-slab vapor and/or indoor air samples to help identify buildings or groups of buildings that need to be sampled. Soil vapor samples are used to determine the potential for vapors to accumulate beneath buildings. Soil vapor samples are not the same as soil samples. Sub-slab vapor samples are collected to characterize the nature and extent of vapor contamination in the soil immediately beneath a building with a slab. In buildings without a slab, crawl spac
