Chemists in the 19th century were the first to inquire about the smallest amount of airborne material detectable by the nose. As they suspected, the human sense of smell proved very sensitive to some materials, with reliable detection of a few parts per trillion parts of air, and relatively insensitive to others. In recent times, thresholds even an order of magnitude below parts per trillion have been measured. The green bell pepper odorant, 2-methoxy-3-isobutylpyrazine, with a threshold of 0.5 ppt, provides an example (see Table 1).
KeywordsWeber Fraction Isoamyl Acetate Odor Identification Odor Quality Odor Experience
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