The effect of penetration factor, deposition, and environmental factors on the indoor concentration of PM2.5 sulfate, nitrate, and carbon Page: 1 of 6
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THE EFFECT OF PENETRATION FACTOR, DEPOSITION, AND
ENVIRONMENTAL FACTORS ON THE INDOOR CONCENTRATION
OF PM2.5 SULFATE, NITRATE, AND CARBON
TL Thatcher' *, MM Lunden', RG Sextro, S Hering2, and NJ Brown'
Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, 1
Cyclotron Rd., Berkeley, CA USA 94720
2Aerosol Dynamics Inc., 2329 Fourth Street, Berkeley, CA USA 94710
ABSTRACT
Indoor exposure to particles of outdoor origin constitutes an important exposure pathway. We
conducted an intensive set of indoor particle measurements in an unoccupied house under
differing operating conditions. Real-time measurements were conducted both indoors and
outdoors, including PM2.5 nitrate, sulfate, and carbon. Because the time-scale of the
fluctuations in outdoor particle concentrations and meteorological conditions are often similar
to the time constant for building air exchange, a steady state concentration may never be
reached. The time-series experimental data were used to determine the effect of changes in
air exchange rate and indoor/outdoor temperature and relative humidity differences on indoor
particle concentrations. A multivariate regression was performed to investigate the difference
between measured indoor concentrations and results from a simple time-dependent physical
model. Environmental conditions had a significant effect on indoor concentrations of all three
PM2.5 species, but did not explain all of the model variation.
INDEX TERMS
Particle, deposition, penetration factor, ammonium nitrate, ammonium sulfate, carbon
INTRODUCTION
Particulate air pollution is associated with increased morbidity and mortality even at the
generally low levels of pollution in United States cities (Samet, et al., 2000). The exact
compounds and/or particle size ranges responsible for these health effects have not yet been
determined. Exposures to particles of outdoor origin which occur while indoors may
constitute a significant fraction of the overall exposure to hazardous particles since typically
people spend up to 90% of their time indoors (Jenkins, et al., 1992, Robinson and Nelson,
1995). Indoor concentrations of particles of outdoor origin can be on the same order as
outdoor concentrations (Ott et al., 2000; Riley et al., 2001).
Separating the effects of deposition and penetration in a full-scale house is difficult. In this
study, we measured the indoor and outdoor concentrations of PM 2.5 nitrate, sulfate, and
carbon over a period of several days. A simple time dependent physical model is then used to
determine the penetration factor, defined as the fraction of particle in the infiltrating air which
pass through the building shell, and deposition loss rate for each compound. The difference
between the modeled and measured values is used in a multiple variable regression to
examine the effect of changes in temperature, relative humidity, and air exchange rate on
model fit.
METHODS
The experiments were performed in a 134 m2 home in Clovis, California. The home was
constructed in 1972, with a stucco exterior and sliding aluminum frame windows. The house
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Thatcher, T. L.; Lunden, M. M.; Sextro, R. G.; Hering, S. & Brown, N. J. The effect of penetration factor, deposition, and environmental factors on the indoor concentration of PM2.5 sulfate, nitrate, and carbon, article, April 15, 2002; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc737122/m1/1/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.