ABSTRACT
A threshold value is not a fixed physiological fact or a physical constant but is a statistical point representing the best estimate from a group of individual scores. Two types of thresholds can be evaluated: detection and recognition. Another term, the odor emission rate, is often used to describe the severeness of the downwind impact, i.e., the problem a typical odor source creates at downwind locations. In the context of air pollution field work, the hedonic tone is often irrelevant. Perception of an odor is based on the combination of frequency of occurrence, odor character, and odor intensity. Even pleasant odors can become objectionable if they persist long enough. Olfactory studies have revealed interesting information regarding odor perception. As an illustration of the complexity of odor perception, pungency stimulation shows an increased response to odors from a continuous or quickly repetitive stimulus during a short term exposure.
