David Folkes, P.E. (CO) has worked on a large number of vapor intrusion (VI) projects across North America and overseas over the past 20 years. Additionally, he has been extensively involved with development of VI practice and guidance in the US. He helped several state agencies with VI guidance development and training and was a member of the ITRC VI and Petroleum VI teams, including serving as a trainer for the mitigation portions of both documents. He has overseen the design, installation, and operation of VI mitigation systems at new and existing buildings impacted by VOCs, PHCs, and landfill gas. Dave has evaluated and designed a wide variety of VI mitigation systems, including active and passive systems using a variety of barrier and venting technologies, HVAC modifications, ICs, and other vapor control strategies. His research and publications have focused on mitigation system performance, aerated floor systems, and use of VI pathway principles for mitigation system design.