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Keywords:

  • Bioaerosol;
  • UV-APS;
  • Coarse particles;
  • Time-resolved measurement;
  • Indoor air quality;
  • Human activity

Abstract

This study is among the first to apply laser-induced fluorescence to characterize bioaerosols at high time and size resolution in an occupied, common-use indoor environment. Using an ultraviolet aerodynamic particle sizer, we characterized total and fluorescent biological aerosol particle (FBAP) levels (1–15 μm diameter) in a classroom, sampling with 5-min resolution continuously during eighteen occupied and eight unoccupied days distributed throughout a one-year period. A material-balance model was applied to quantify per-person FBAP emission rates as a function of particle size. Day-to-day and seasonal changes in FBAP number concentration (NF) values in the classroom were small compared to the variability within a day that was attributable to variable levels of occupancy, occupant activities, and the operational state of the ventilation system. Occupancy conditions characteristic of lecture classes were associated with mean NF source strengths of 2 × 106 particles/h/person, and 9 × 104 particles per metabolic g CO2. During transitions between lectures, occupant activity was more vigorous, and estimated mean, per-person NF emissions were 0.8 × 106 particles per transition. The observed classroom peak in FBAP size at 3–4 μm is similar to the peak in fluorescent and biological aerosols reported from several studies outdoors.