Size and other characteristics of airborne particles are considered with regard to predicting their behavior in air, the hazard they present to the lung, and their production during industrial processes. Emphasis is placed on the difficulties involved in measuring particles. Martin's and Feret's diameters and the projected area diameter are considered. Statistical considerations are outlined dealing with the problem of polydispersity and skewed distribution of particle sizes. A discussion of the proper selection of measurement techniques covers optical microscopy, including preparation of specimens, the use of reticles and calibration procedures, as well as electron microscopy, impaction devices, centrifugal collectors, light scattering and measurement of electrical charge.
The Industrial Environment - Its Evaluation and Control, NIOSH, Cincinnati, Ohio, Chapter 14