2.2 Sensory Characteristics of Odors An odor can be characterized by its absolute threshold, its intensity, its quality, and its affective tone or pleasantness-unpleasantness dimension. Determinations of thresholds of odor perception and measurements of odor intensity are considered in Sections 2A and Section respectively. Discussion of measurements of quality and odor surveys are reserved for Section 4 It is important to recognize throughout that any program of odor measurement should be related to realistic objectives. For example, if the odor from a landfill operation is to be controlled by masking agents, it is to appraise odor intensities or threshold levels; a more appropriate measurement would scribe the changed odor quality or character and would assay its acceptability to the people in the community. On the other hand, a nonselective method of odor reduction, such ventilation or activated carbon adsorption, may well be monitored by measurements of intensity or by threshold dilution techniques. 2.3 Psychophysics and the Measurement of odor Perception G.T. Fechner is generally considered to be the founder of psychophysics, which he defined as the exact theory of the functionally dependent relations of body and soul, or more