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Sustainable Vapor Intrusion Controls – Designing an Effective Passive System

Under certain conditions and with the appropriate design, passive systems can be successful in mitigating the vapor intrusion pathway and have the advantage of being greener and more sustainable over the long term. A successful passive vapor intrusion control system is likely to require more extensive construction efforts, particularly for an existing building, because the system requires comprehensive sealing of all vapor intrusion pathways. These efforts are likely to result in higher initial capital costs and short-term disruption to building users, but these elements may be offset by lower long-term operation and maintenance efforts and avoidance of aesthetic and other impacts on property owners that may be inherent in continuous operation of an external fan-based system. These reduced operation and maintenance requirements and impacts are also likely to make passive systems preferable to the building owners, particularly in residential applications. Documenting the effectiveness of these systems is likely to rely initially on indoor air sampling, but long-term monitoring can be limited to confirming that the systems remain intact. In this paper, we describe some of the conditions and design requirements for implementing successful passive vapor intrusion control systems at both residential and commercial buildings. We also present monitoring data collected at residential properties and a commercial office building where passive systems were successfully implemented.