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INDOOR/OUTDOOR PARTICLE SIZE DISTRIBUTIONS MEASURED IN SELECT HOMES IN THE RALEIGH-DURHAM-CHAPEL HILL, NC AREA
Citation:
Vette, A F., R W. Williams, M Riediker, AND J. Thornburg. INDOOR/OUTDOOR PARTICLE SIZE DISTRIBUTIONS MEASURED IN SELECT HOMES IN THE RALEIGH-DURHAM-CHAPEL HILL, NC AREA. Presented at American Association for Aerosol Research, Portland, OR, October 15-19, 2001.
Impact/Purpose:
The primary study objectives are:
1.To quantify personal exposures and indoor air concentrations for PM/gases for potentially sensitive individuals (cross sectional, inter- and intrapersonal).
2.To describe (magnitude and variability) the relationships between personal exposure, and indoor, outdoor and ambient air concentrations for PM/gases for different sensitive cohorts. These cohorts represent subjects of opportunity and relationships established will not be used to extrapolate to the general population.
3.To examine the inter- and intrapersonal variability in the relationship between personal exposures, and indoor, outdoor, and ambient air concentrations for PM/gases for sensitive individuals.
4.To identify and model the factors that contribute to the inter- and intrapersonal variability in the relationships between personal exposures and indoor, outdoor, and ambient air concentrations for PM/gases.
5.To determine the contribution of ambient concentrations to indoor air/personal exposures for PM/gases.
6.To examine the effects of air shed (location, season), population demographics, and residential setting (apartment vs stand-alone homes) on the relationship between personal exposure and indoor, outdoor, and ambient air concentrations for PM/gases.
Description:
Particle size distributions were measured indoors and outdoors of six residences in the Raleigh-Durham-Chapel Hill, NC area to characterize the factors affecting particle concentrations in the indoor environment, including infiltration of outdoor aerosols. Size resolved particle number concentrations were measured using a Scanning Mobility Particle Spectrometer (SMPS; TSI Model 3936) and an Aerodynamic Particle Sizer (APS; TSI Model 3320). Indoor and outdoor aerosol concentrations were alternately measured through a ball-valve switching manifold. Concurrent measurements of indoor air exchange rates were made continuously by releasing sulfur hexafluoride and monitoring concentration decay using a portable gas chromatograph (Lagus Applied Technologies).
In southeast Raleigh, data was collected over multiple seasons as part of the National Exposure Research Laboratory's Research Triangle Park Particulate Matter Panel Study during fall 2000 (1 home), winter and spring 2001 (4 homes). One home was monitored in Chapel Hill during summer 2000 and one in Durham during spring 2001. The housing stock varied considerably in size (one and two story; 1000-2500 square feet), construction (brick and wood siding) and age (12-46 years).
Results from all of the houses show that particles between 0.1 and 1 micrometer had the highest indoor/outdoor particle concentration ratios during non-source periods. However, average indoor/outdoor ratios in this size region varied considerably from about 0.5 to 0.9, both between homes and within the same home during different seasons. Hourly air exchange rates also varied between homes and seasons, and generally ranged from about 0.2/h to 3/h. Air exchange rates in the older homes varied by a factor of 3 to 4 between seasons, even when doors and windows were closed. The temperature differential between indoors and outdoors was very influential in affecting air exchange rates in older homes. Consequently, indoor/outdoor particle concentration ratios in older homes were higher and more seasonally variable than in newer homes.
This work has been funded wholly or in part by the United States Environmental Protection Agency under Contract No. 68-D99-012 to the Research Triangle Institute. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.