Aerodynamic diameter is defined as the physical diameter of a unit density sphere that settles through the air with a velocity equal to that of the

particle in question. It is the most significant aerosol size parameter because it determines the particle’s behavior while airborne. Particles exhibiting the

same airborne behavior have the same aerodynamic diameter, regardless of their physical size, shape, density, or composition.

Knowledge of a particle’s aerodynamic diameter allows you to determine:

+ If and where the particle will be deposited in the

human respiratory tract

+ How long the particle will remain airborne in the atmosphere or in an aerosol

+ Whether the particle will penetrate a filter, cyclone, or other particle-removing device

+ Whether the particle will enter a particle-sampling system

+ Whether the particle will penetrate a pipe, tube, duct, or channel

Why is the Model 3321 Superior?

Traditionally, TSI has designed its time-of-flight spectrometers to provide the truest high-resolution measurements of aerodynamic size. With the

introduction of the Model 3320 in 1997, TSI produced the first aerosol spectrometer capable of detecting coincidence. The Model 3321 builds upon

this accomplishment with a redesigned nozzle configuration and improved signal processing. These enhancements provide greater small-particle

sizing efficiency, improved accuracy of mass-weighted distributions, and virtual elimination of false background counts. Coincidence affects

all single-particle-counting instruments. It occurs when more than one particle is present in an instrument’s measuring volume. This can distort

sizing information and lead to underreporting of particle concentration.