For particles greater then 1 micron, diffusion due to gravitational settling is dominant. For particles less than 0.5 microns the terminal velocity is approximately zero. Even though the overall bioaerosol may have a neutral charge the bioaerosol particles themselves are invariably charged to a greater or lesser degree in accordance with Boltzman's distribution. Aerosol particles interact with electromagnetic radiation primarilly through reflection, refraction, absorption and scattering. In both cases transparent particles move towards heat sources because they act as a lens thereby focusing energy on the distal side.
Opaque particles move in the opposite direction.
In laminar flow particles are carried along the airstream with the air molecules, but on a change in direction the heavier bioaerosol particles will break the streamlines. As a result, the particles may deposit on curved or angled surfaces. The particle velocity is given by Stokes Law. For laminar flow in which the particle is turbulent, deposition is more likely to occur. For turbulent flow, deposition is less likely.