You are here:
INDOOR/OUTDOOR AEROSOL CONCENTRATION RATIOS DURING THE 1999 FRESNO PARTICULATE MATTER EXPOSURE STUDIES AS A FUNCTION OF SIZE, SEASON, AND TIME OF DAY
Citation:
Vette, A F., A W. Rea, P. A. Lawless, C. E. Rodes, G F. Evans, V R. Highsmith, J P. Creason, AND L S. Sheldon. INDOOR/OUTDOOR AEROSOL CONCENTRATION RATIOS DURING THE 1999 FRESNO PARTICULATE MATTER EXPOSURE STUDIES AS A FUNCTION OF SIZE, SEASON, AND TIME OF DAY. Presented at PM 2000 AWMA Conference, Charleston, SC, January 24-28, 2000.
Description:
The 1999 Fresno particulate matter exposure studies tools place in February (winter season) and April/May (spring season) for two periods of four weeks. During that time, near-continuous measurements of indoor and outdoor aerosol concentrations were made with a scanning mobility particle spectrometer (TSI SMPS) and an optical particle counter (PMS LASX). Combined, these instruments provide particle size distribution from about 0.01 to 3 um. This data can be used to identify near real-time perturbations, not only in aerosol concentration, but also aerosol size.
The indoor concentrations were measured in a vacant apartment used as an office and sampling site for the project. A switching manifold was used to alternately collect samples of five minute duration indoors and outdoors. During the winter season, the HVAC system was run continuously throughout the monitoring period. During the spring season, the HVAC system was run intermittently and was more representative of the community residences. Doors and windows were kept closed in both seasons.
Although the aerosol number concentration measurements from the SMPS and LASX require a knowledge of particle specific gravity to compute aerosol mass concentrations, the ratio of indoor to outdoor concentration as a function of particle size does not. The concentration ratio provides information about the effects of ambient concentration levels on indoor concentration, while the size-dependence of the ratio gives information about HVAC effects on the indoor concentration.
During the winter season, the HVAC system was run continuously and resulted in filtering the indoor air substantially, while in the spring season, the filtration effect was smaller. During one test period, the HVAC system was shut down for a period of about 16 hours, including the overnight period when the apartment was unoccupied. During that time, the indoor/outdoor ratio data provided information about the aerosol penetration into the building. Indoor/outdoor particle number density and ratios over the full size spectrum were used to evaluate different sources of particles in the indoor and outdoor environment. The results indicate that activities such as opening and closing doors and windows, even for brief periods of time, greatly affects aerosol penetration. In addition, seasonal differences were observed in particle size distribution with fine aerosols (PM2 5) dominating during winter and coarse aerosols dominating during spring.
This work has been funded wholly or in part by the U.S. Environmental Protection Agency under contract #68D50040 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 an endorsement or recommendation for use.