A dynamic flow type of human olfactometer was developed.
Twenty-six healthy male adults were used for testing "detection threshold" of ten kinds of standard test odorants diluted with nujol. They were β-phenylethyl alcohol, cycloten, iso-valeric acid, γ-undecalactone, skatol, exalotolide, phenol, dl-camphor, diallyl sulfide and acetic acid. Distribution of "detection threshold" of these odorants showed almost a normal curve. Exposures to β-phenylethyl alcohol and skatol showed a large coefficient of variation in "detection threshold". On the contrary, acetic acid and cycloten showed a small deviation.
Five healthy male adults were exposed to iso-valeric acid (10-5) using the olfactometer in the odor exposure chamber, and the function of concentration maintenance (TAF), heart rate, blood pressure and brain waves were measured. The effect of NH3 (4ppm) and H2S (0.12ppm) on the above physiological functions was also studied. Odorant concentration in the range of "detection threshold" did not cause any significant change in TAF, heart rate, blood pressure and brain waves, but odorant concentration over "recognition threshold" affected the above physiological functions.
From these results, it may be presumed that the acceptable limit of odor concentration exhibiting the lowering of physiological functions is in the range of "recognition threshold". This limit of odor intensity may correspond to three point five according to the six-points intensity scale.