Estimating Soil Gas Flow Rates and Identifying Entry Routes in a Dwelling Using Multiple Perfluorocarbon Tracers

by Thomas M. Kenney, NAHB Natl Research Cent, United States,
Ban-Huat Song, NAHB Natl Research Cent, United States,
Jordan Fan, NAHB Natl Research Cent, United States,
Mark Nowak, NAHB Natl Research Cent, United States,



Document Type: Proceeding Paper

Part of: Environmental Engineering

Abstract:

Passive monitoring of indoor air and below basement floor (subslab) soil gas for radon and perfluorocarbon tracer (PFT) gas concentration was conducted to investigate the influence of ambient outdoor temperature on soil gas entry. Multiple PFT gases were used to quantify soil gas flow rates and identify entry routes into the basement of a residence in the metropolitan Washington D.C. area. Two distinct PFT gases were used to trace the movement of soil gas. One type (soil-PFT) was deployed in the soil adjacent to foundation walls and a second type (slab-PFT) was placed in the gravel below the basement floor. Detection of the soil-PFT in the basement sump suggested infiltration of outdoor air through the soil and gaps between the soil and basement wall to the subslab area. PFT concentrations were monitored in the basement and in the sump to estimate outdoor air flow rate into the subslab area and into the basement. Ambient outdoor temperature was indicated as having a significant influence on radon concentration as evidenced in bi-weekly, monthly and seasonal observations.

Subject Headings: Soil gas | Gas flow | Basements | Slabs | Flow rates | Flow measurement | Soil pollution

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