Original article: 2005:42: Vander Wood
The traditional method for determining the particle size distribution in stack emissions is gravimetric analyses of material collected on cascade impactors. But new sources have particulate loadings so low that sampling times of many hours (or days) are required to collect enough particulate for gravimetric techniques.
Collection of Method 5 samples on appropriate filters followed by microscopical analysis of the collected material offers an alternative method of particle size distribution measurement, with sampling times of only minutes to hours required. Particle sizes down to 0.1 um diameter can be measured, and the particle size distribution reported in customizable cutoffs. In addition to mass fraction, number fraction of particles and estimates of particle surface area fraction can be determined for each size category.