This document reports the design of an electrical instrument which utilizes a variable capacitance in one leg of an R-C feedback network to provide discriminatory information regarding the air stream particulate materials. Sufficient testing was performed on the breadboard to validate system concept. The current instrument is counting fiber mass and indicating fiber diameters to yield an approximate count of individual fibers. Its operational range has a lower limit of 10000 fiber/cu m and an upper limit internally restricted for this breadboard state to 2 x 10 to the 8th power fibers/cu m. The program scope did not allow completion of a prototype design; therefore, emphasis is placed on recommendations to complete design efforts.