Indoor bioaerosol dynamics

Nazaroff, William W

Most indoor airborne microbial material is found on particles in the diameter range 0.1-10 lm. This range of diameters corresponds to six orders of magnitude in particle mass. In part because of the large range, size is a major determinant of indoor airborne particle behavior (Nazaroff, 2004) . The behavior of larger particles is strongly influenced by their mass. Gravitational settling and inertial impaction are important deposition mechanisms. The smaller particles in this size range follow airstreams more closely. Transport mechanisms leading to the departure of smaller particles from air streamlines include Brownian motion. Generally, the efficiency of filtration, the likelihood of deposition somewhere in the respiratory tract, and the rate of deposition onto indoor surfaces are all considerably smaller for particles with diameters in the range 0.1-1 lm as compared with particles with diameters in the range 1-10 lm.