AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Indoor Bioaerosol Dynamics: Fluorescent Particles in a College Classroom
SEEMA BHANGAR, Elizabeth Heredia, J. Alex Huffman, William Nazaroff, University of California, Berkeley, CA
Abstract Number: 374 Working Group: The Indoor Microbiome
Abstract Our research aims to characterize bioaerosol emissions, behavior, and fate in common, occupied indoor environments, using particle fluorescence as an indicator of biological origin. In a weeklong monitoring study conducted in a mechanically ventilated university classroom in March 2012, we observed strong transient increases associated with janitorial activities in the number concentration of fluorescent particles (N$_F) and in the indoor/outdoor concentration ratio of all particles (I/O). We also observed increases in N$_F, I/O and in the ratio of fluorescent to total particles (N$_F/N$_T) at the beginning and end of class sessions when human movements in the room were most vigorous.
Focusing on the aggregate behavior of 1-20 micro-meter particles, preliminary analyses show that during weekdays, when classes were in session and the air-handling system was on, mean levels of N$_F, N$_F/N$_T, and I/O were 1.6 cm$^(-3), 23%, and 0.82, respectively. In the evenings, when the room was used less intensively but before the air handling system was turned off, mean levels of N$_F, N$_F/N$_T, and I/O were reduced to 0.77 cm$^(-3), 15%, and 0.49. Overnight and on weekends, when occupancy was zero and the air handling system was off, fluorescent particle levels decreased by an order of magnitude. The mean N$_F, N$_F/N$_T, and I/O during these times were 0.15 cm$^(-3), 3.8%, and 0.40. All three indicators varied strongly with particle size. Mean weekday values of N$_F/N$_T varied from 2% for 1 micro-meter particles to 68% for 10 micro-meter particles.
The data are being further interpreted to assess total and fluorescent particle emission and decay rates as functions of key influencing variables: human occupancy, building design and operational parameters, and particle size. Repeated sampling in this classroom and in other common indoor environments is planned.