Estimation of bias with the single-zone assumption in measurement of residential air exchange using the perfluorocarbon tracer gas method
AuthorVan Ryswyk, K; Wallace, L; Fugler, D; MacNeill, M; Heroux, ME; Gibson, MD; Guernsey, JR; Kindzierski, W; Wheeler, AJ
Source TitleIndoor Air: international journal of indoor air quality and climate
University of Melbourne Author/sWheeler, Amanda
AffiliationMelbourne School of Population and Global Health
Document TypeJournal Article
CitationsVan Ryswyk, K., Wallace, L., Fugler, D., MacNeill, M., Heroux, M. E., Gibson, M. D., Guernsey, J. R., Kindzierski, W. & Wheeler, A. J. (2015). Estimation of bias with the single-zone assumption in measurement of residential air exchange using the perfluorocarbon tracer gas method. INDOOR AIR, 25 (6), pp.610-619. https://doi.org/10.1111/ina.12171.
Access StatusOpen Access
UNLABELLED: Residential air exchange rates (AERs) are vital in understanding the temporal and spatial drivers of indoor air quality (IAQ). Several methods to quantify AERs have been used in IAQ research, often with the assumption that the home is a single, well-mixed air zone. Since 2005, Health Canada has conducted IAQ studies across Canada in which AERs were measured using the perfluorocarbon tracer (PFT) gas method. Emitters and detectors of a single PFT gas were placed on the main floor to estimate a single-zone AER (AER(1z)). In three of these studies, a second set of emitters and detectors were deployed in the basement or second floor in approximately 10% of homes for a two-zone AER estimate (AER(2z)). In total, 287 daily pairs of AER(2z) and AER(1z) estimates were made from 35 homes across three cities. In 87% of the cases, AER(2z) was higher than AER(1z). Overall, the AER(1z) estimates underestimated AER(2z) by approximately 16% (IQR: 5-32%). This underestimate occurred in all cities and seasons and varied in magnitude seasonally, between homes, and daily, indicating that when measuring residential air exchange using a single PFT gas, the assumption of a single well-mixed air zone very likely results in an under prediction of the AER. PRACTICAL IMPLICATIONS: The results of this study suggest that the long-standing assumption that a home represents a single well-mixed air zone may result in a substantial negative bias in air exchange estimates. Indoor air quality professionals should take this finding into consideration when developing study designs or making decisions related to the recommendation and installation of residential ventilation systems.
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