Indoor bioaerosol dynamics

Nazaroff, William W

A fundamental principle that is usefully applied in quantitative, mechanistic studies of indoor environmental quality is material balance: Stuff is conserved. On a time-averaged basis, the sum of the rates of supply of a bioaerosol component to the indoor air must balance the sum of the rates of removal. This quantitative balance provides a basis for connecting rates of processes to concentrations of bioaerosol components. Figure 6 presents schematic representations of indoor environments that can be used to formulate material balance equations. Consider a residential space ( Figure 6a ). In this representation, three processes can add bioaerosol material to the indoor air: (i) natural ventilation through designed openings (at rate Q N 9 C o ); (ii) infiltration through leaks in the building envelope (p 9 Q L 9 C o ); and (iii) direct indoor emissions (E). (To the extent that tracked-in microbes contribute to the indoor bioaerosol load, this process would be included in the direct indoor emission term, E.) Three processes can remove bioaerosol material: (i) ventilation airflow out of the building ([Q N + Q L ] 9 C); (ii) filtration in the recirculating airflow (g R 9 Q R 9 C); and (iii) deposition onto room surfaces (bVC).