This paper introduces a new parameter for describing air classifier performance, “Total Efficiency”, found by first calculating the fractions recovered of both light and heavy fractions at specific air speeds and then multiplying the two fractions. Total Efficiency can be plotted against air speed, and such plots yield information about peak efficiencies and sensitivity to air flow rate variations. This method allows the comparison of different air classifiers and also leads to a technique in which the data can graphically express contamination of the light or heavy fraction at different air speeds. These curves can then be used to determine the optimum air speed in terms of market value of the product produced. Data on three different throat designs — the zigzag throat and two variations of the zigzag, are used to illustrate the method.