Here At Last! DTSC's 2022 Vapor Intrusion Advisory

Last month, the California Department of Toxic Substances Control (“DTSC”) issued its long-awaited “Vapor Intrusion Update” (“Advisory”) which is intended to guide the selection of attenuation factors (“AFs”) at contaminated sites overseen by DTSC.

For folks frantically Googling the term “attenuation factors,” I'll save you some time: attenuation factors are merely estimates of the decimal fraction of vapor phase chemicals that pass through a barrier and enter the indoor space of a structure. So, for example, an attenuation factor of 0.03 means that an estimated 3% of vapor phase chemicals pass through a barrier and enter an indoor structure.

DTSC's one-page Advisory is broken up into three sections: “Site Screening,” “Delineation,” and “Mitigation and Remediation.” I'll underline the good stuff: