Size of Smoke Particles
In the problem of smoke production, the size of the particle is of great importance. Being a physical quantity it can easily be correlated with such physical properties as settling, diffusion, coagulation, and evaporation. These factors are more important in connection with toxic smokes, since there the penetration factor must be considered.
Smoke appears to consist of particles of all sizes from 10⁻³ cm., which may just be resolved by the unaided eye, to molecular dimensions, 10⁻⁸ cm. The larger particles settle out most rapidly and so do not remain long in suspension.