Quantifying the Influence of Stack and Wind Effects on Vapor Intrusion

ABSTRACT

This article develops mathematical relationships for quantifying how the stack effect, wind effect, and effective leakage area influence the rates of subslab soil gas entry and outdoor air infiltration into residential buildings. The equations developed in the article are based on combining existing theory for air infiltration into buildings with existing vapor intrusion modeling methods. Use of the equations for estimating the subslab soil gas attenuation factor for assessing inhalation exposure via vapor intrusion into residential buildings is illustrated with example simulations using 1 year of hourly temperature and wind speed data from a Northeastern U.S. city and with several distributions of the effective leakage area from a U.S. residential air leakage database. The simulation results make clear that the soil gas entry rate and the building's ventilation rate are positively correlated, and this correlation mutes the influence of stack and wind effects on the subslab attenuation factor. The examples also suggest that the subslab attenuation factor for most residential buildings is likely to be less than 0.003 most of the time.

Key Words:

• vapor intrusion
• attenuation factor
• stack effect
• wind effect
• soil gas entry
• air infiltration