Measurement of Odor Threshold by Triangle Odor Bag Method

The detection thresholds of odor substances analyzed in field investigations were measured by the triangle odor bag method. The number of substances used for the experiment is 223. The experiment was carried out from 1976 to 1988. As the results of the experiments, the odor thresholds were distributed over the concentration of large range depending on the odor substances. Isoamyl mercaptane exhibited the lowest threshold (0.77ppt), and propane exhibited the highest threshold (1500ppm). The distribution of thresholds expresses the normal distribution. Sulfur compounds with the exception of sulfur dioxide and carbon disulfide have the comparatively low threshold. It is showed the tendency that threshold becomes low as the increase of molecular weight in a certain range of molecular weight. When the dispersion of odor thresholds for the same substance was shown at the ratio of the highest to the lowest odor threshold tested, the dispersion of odor thresholds was about 5 at the maximum. The thresholds of 223 substances measured by our laboratory were considered to be the average values with small bias comparatively.