Preface

This document provides guidance on identifying and addressing current and potential human exposures to contaminated subsurface vapors associated with known or suspected volatile chemical contamination. While vapor intrusion may also occur with "naturally-occurring " subsurface gases (e.g., radon, methane and hydrogen sulfide), the document discusses soil vapor intrusion in terms of environmental contamination only. The document is organized into five sections: Section 1 introduces the concept of soil vapor intrusion, associated human exposure issues, factors affecting soil vapor intrusion, factors affecting indoor air quality, and the general approach to evaluating vapor intrusion; Section 2 provides guidance on collecting appropriate and relevant data that can be used to identify current or potential human exposures; Section 3 discusses how the investigation data are evaluated, recommends actions based on the evaluation, and presents tools that may be used when determining appropriate actions to address exposures; Section 4 provides an overview of soil vapor intrusion mitigation methods and basi