Tech Focus: Radon Monitoring for Vapor Intrusion
When reviewing indoor air data, have you noticed challenges determining if the contaminants found in indoor air data are due to vapor intrusion or indoor sources? Many volatile organic compounds (VOCs) responsible for vapor intrusion risk are also found in ambient air, building materials, or consumer products, which makes interpreting post-construction indoor air monitoring results quite difficult. While simultaneously collecting ambient air and sub-slab soil gas samples may help illuminate the source of contaminants, it is not always definitive, and conducting multiple rounds of sampling negatively impacts both budget and schedule.
One option to avoid delays is to use a surrogate for VOCs that does not have typical indoor or ambient air sources, such as radon. Radon is naturally associated with various geology in the United States and thus is often present in soil gas at detectable concentrations. A site-specific cross-slab attenuation factor (AF), or an estimate of the amount of vapor phase chemicals that pass through barriers and enter indoor space, can be determined by collecting sub-slab soil gas and indoor air radon data with field instruments including the DURRIDGE RAD7. Once a site-specific AF is determined and an indoor air radon baseline is established, long-term vapor intrusion monitoring may be satisfied by continuous radon monitoring via wireless sensors mounted throughout a building, helping avoid the potential for obfuscation of indoor air VOC data.
Langan recently implemented this real-time radon monitoring method on multiple projects in the San Francisco Bay Area, leading to regulator acceptance and favorable results.
About Jessica Schaettle
Jessica Schaettle is a Project Engineer with five years of experience working on various environmental projects in California. She regularly designs vapor and methane mitigation systems for buildings and oversees field investigations including, but not limited to, indoor air monitoring, sub-slab soil gas sampling, and groundwater sampling for sites under local and federal regulatory agencies. Most recently, her practice has focused on identifying alternate sampling and monitoring approaches to limit the impact of indoor air sources on vapor intrusion assessments.