Dynamic olfactometry variability in determining odor dllutions-to-threshold

When conducting research on odor abatement technologies, a weak link has been the inability to place a precise quantifying number on odor strength that can be accurately reproduced within the same laboratory and between laboratories. Olfactometry is one of the most accepted means for evaluating odor samples. However, insufficient effort has been made to determine variation between or among individual panelists. This study was designed to analyze three odor sample strengths over a three-day period by two odor panels, each composed of eight panelists. Three sample strengths were presented randomly to each panelist three times within each session. Whole-panel variation ranged from a 22% to 50% difference in reported odor units for the same sample, depending on sample strength. Using two different airflow rate calibrations resulted in a 9% to 28% difference in odor units for the same sample, depending on sample strength. Panelist variation ranged from 4.3- to 7.1-fold, depending on sample strength, although panelist standardization slightly reduced this variation. Sample order had no effect on odor strength determination. A learning curve for individual panelists appeared to exist, as odor unit evaluation for later observations were 3.8 and 4.1 times greater than similar evaluations for the first samples. Variation between panelists is approximately the same as variation among evaluations done by the same individual; efforts should be made to reduce both these variations. To be able to detect differences in odor concentrations between control and treatment samples, large reductions in odor concentrations with several air samples are needed to accurately detect a significant reduction in odor.