Optical particle size measurements of hygroscopic smokes in laboratory and field environments

Optical particle size analyzer (PSA) measurements of hygroscopic smokes are reported from experiments conducted in laboratory chambers and in field tests. Three different instruments were used: a particle sizing interferometer; a Climet (model 211); and a Particle Measurement Systems PSA (model CSASP-100-HC). Field measurements were made in relative humidity conditions ranging between 65 and 97%. The results indicate that the size distributions are at least bimodal-not log-normal-and that mean particle diameter does not appear to increase with increasing relative humidity.