Small liquid droplets or aerosols may form from a flashing stream, with the possibility of transport away from the leak by wind currents. Liquid droplets may also be present because they are carried over in a two-phase flow, e.g. during pressure relief of a reactor. This can be promoted by large relief pressures and high reactor fill levels. Solids suspended in reactants (e.g. a heterogeneous catalyst) may also be entrained in a liquid flow.
Reference: adapted from Chemical Process Safety, Fundamentals with Applications, Daniel A.Crowl,Joseph F.Louvar, Page 119, Third Edition,2011