Standard Practice for Referencing Suprathreshold Odor Intensity

Abstract

These practices are designed to outline two preferred procedures for referencing the odor intensities of any odorous material in the suprathreshold region on the ASTM Odor Intensity Referencing Scale. The method by which the reference odorant vapors are to be presented for evaluation by a panel of at least eight independent judgments is specified, but the manner by which the test sample is presented will depend on the nature of the sample, and is not defined herein. The methods, where a geometric progression scale with a ratio of 2 is recommended, are generally done by comparing the odor intensity of the sample to the odor intensities of a series of concentrations of the reference odorant 1-butanol (n-butanol). The two procedures differ in the method by which the diluted 1-butanol vapors are prepared. In Procedure A (dynamic scale method), a dynamic-dilution apparatus is used. This is equipped with a series of sniffing ports from which constant concentrations of 1-butanol emerge at constant volumetric flow rates in air. In Procedure B (static-scale method), a series of Erlenmeyer flasks containing known concentrations of 1-butanol in water is used.