Standardized procedure for expressing odor intensity

We wish to propose a standardized way to express the perceived intensity of odors. There are currently in use various procedures for the assessment of odor magnitude. These techniques include (a) equal intensity matches (where various levels of one odorant are matched in perceived magnitude to another odorant), (b) threshold measures (where odor intensity is expressed in terms of multiples of threshold con-centration), (c) one or another type of category (interval) scaling procedure, and (d) ratio scaling procedures. Each technique yields its own scale of measurements. Often, the information obtained in one experiment would be useful to other investigators, but the lack of a standardized scale and unit for odor intensity measurement precludes the exchange of useful measurements. In many instances it is impossible for the reader of a report to decide whether an experimenter used stimuli of high, medium, or low intensity. The need for a standardized scale is particularly necessary in olfaction, where the potential stimuli (odorants) number in the thousands and where the stimu-lating effectiveness of one odorant may be very different from that of another. We propose that workers in olfaction use a reference scale that is based on tech-niques of sensory measurement collectively known as 'ratio scaling ' methods. We have noted that when 1-butanol vapor is diluted in air, and its various concentrations are presented to subjects by dynamic, flowing procedures, a relatively simple power func-tion, S=kC, where nx0.66, related judged odor magnitude (5) to concentratio