| This paper presents the results of research on the performance of air-cleaning and air-disinfection systems used for protecting
buildings against intentional releases of biological agents. The air-cleaning technologies addressed include dilution ventilation, filtration,
and ultraviolet germicidal irradiation. A 40-story commercial office building is modeled using typical occupancy levels and leakage rates
for doors, walls, and floors. A steady-state single-zone model is used to predict steady-state conditions resulting from the use of various
levels of air cleaning. A transient single-zone model is used to predict transient indoor concentrations from which inhaled doses and
estimated casualties are predicted. A transient multizone model is used to evaluate contaminant dispersion and estimate potential casualties.
Three design-basis attack scenarios are simulated using various biological weapon agents. Predicted casualties are estimated using an
epidemiological model of the dose response curves for each of the agents. The effect of increasing levels of air cleaning is examined under
the attack scenarios to evaluate their effectiveness. Results indicate that high levels of protection are possible for building occupants with
moderate and affordable levels of air cleaning when filtration is combined with ultraviolet germicidal irradiation. Results also suggest that
diminishing returns occur when increased levels of air cleaning are applied. It is hypothesized that the maximum useful size of any
air-cleaning system is defined and limited by building physical characteristics alone. |