US residential building air exchange rates: new perspectives to improve decision making at vapor intrusion sites

Abstract

Vapor intrusion (VI) is well-known to be difficult to characterize because indoor air (IA) concentrations exhibit considerable temporal and spatial variability in homes throughout impacted communities. To overcome this and other limitations, most VI science has focused on subsurface processes; however there is a need to understand the role of aboveground processes, especially building operation, in the context of VI exposure risks. This tutorial review focuses on building air exchange rates (AERs) and provides a review of literature related building AERs to inform decision making at VI sites. Commonly referenced AER values used by VI regulators and practitioners do not account for the variability in AER values that have been published in indoor air quality studies. The information presented herein highlights that seasonal differences, short-term weather conditions, home age and air conditioning status, which are well known to influence AERs, are also likely to influence IA concentrations at VI sites. Results of a 3D VI model in combination with relevant AER values reveal that IA concentrations can vary more than one order of magnitude due to air conditioning status and one order of magnitude due to house age. Collectively, the data presented strongly support the need to consider AERs when making decisions at VI sites.

Three-dimensional vapor intrusion modeling approach that combines wind and stack effects on indoor, atmospheric, and subsurface domains

“…A building with different characteristics and different weather conditions, a different AER would be expected. Reichman et al 22 discuss the variability of AERs in US residential buildings and highlight factors that influence building-specific AERs. The modeling approach presented here directly estimates an AER that is representative of the building and weather (e.g.…”

“…Weather condition and building condition and operation (air conditioning status and occupant preference) are factors that can affect AERs. Recently, Reichman et al 22 reviewed several indoor air quality studies and highlighted important considerations for including accurate estimates of AERs during VI assessments. In addition, they summarized methods for estimating AERs.…”

“…The AER values calculated in this study are specific for the conditions modeled and are fairly low when considered in the context of typical US residential AER values, which often include the contribution of ventilation. 22 …”

“…Reichman et al 22 reviewed the importance of considering building air exchange rates (AERs) when evaluating VI exposure risks; and, other VI researchers have also highlighted the role that factors such as wind flow and temperature can have on contaminant transport in subsurface and also indoor air concentration distribution. 4, 12, 14, 15, 18, 19 Reichman et al 22 noted that existing VI models require users to input generic building pressures and AERs even though indoor air science research provides tools to determine AERs and building pressures based on building characteristics, occupant behavior and weather conditions.…”

“…4, 12, 14, 15, 18, 19 Reichman et al 22 noted that existing VI models require users to input generic building pressures and AERs even though indoor air science research provides tools to determine AERs and building pressures based on building characteristics, occupant behavior and weather conditions.…”