The U.S. Environmental Protection Agency (EPA) Engineering Issue Papers (EIPs) are a series of technology transfer documents that summarize the latest information on selected waste treatment and site remediation technologies and related issues. EIPs are designed to help remedial project managers, on-scene coordinators, contractors and other site managers understand the type of data and site characteristics needed to evaluate a technology for a particular application at their sites. This EIP may also be useful for building owners/operators and home owners who may have a concern about the indoor air quality at their location(s). Each EPA EIP is developed in conjunction with a small group of engineers and scientists from inside EPA and outside consultants, with a reliance on peer-reviewed literature, EPA reports, Web sources, current ongoing research, and other pertinent information. As such, this EIP assembles, organizes, and summarizes the current knowledge on air treatment technologies that are available for removing volatile organic compounds (VOCs) from indoor air. VOCs are one group of chemicals that can easily become gases, or chemical vapors, which can migrate through soil and enter buildings. Well-known examples of VOCs are petroleum products (e.g., gasoline or diesel fuel), dry cleaning solvents (e.g., perchloroethylene, aka perc) and industrial degreasers (e.g., trichloroethylene, TCE). This EIP does not represent EPA policy or guidance.