ABSTRACT
Aerosols are unlike vapors in at least three aspects: they lack an intrinsic property (such as vapor pressure) to become airborne, individual aerosol particles are much larger than the air molecules in which they are suspended, and an aerosol's behavior depends strongly on its size (diameter). The following three mechanisms affect aerosol particles more slowly than inertial and gravitational separation and are therefore usually of secondary importance to aerosols. In short, a particle's Stokes diameter is physically measured, while a particle's aerodynamic diameter is based on its behavior. In principle, one can choose whether to measure an aerosol's Stokes diameter and/or its aerodynamic diameter, but hygienists may be given one but want the other. An aerosol’s hazard is strongly dependent upon where within the respiratory system it will be deposited along with its inherent toxicity at the point of deposition.
