Sensing Instrumentation

The odor panel analyzes each sample for odor strength and intensity by means of two instruments: the Dynamic Dilution Forced-Choice Triangle Olfactometer (or olfactometer) and the Dynamic Dilution Binary Scale Butanol Olfactometer (or butanol wheel). Both instruments comply with standard practice and a
standard method published by the American Society for Testing and Materials (ASTM) and the American National Standards Institute (ANSI), and use the principle of dynamic dilution to deliver varying concentrations of odorous sample to the panelists. Both instruments are manufactured and available
for purchase from RKA.

Dynamic Dilution Forced-Choice Dynamic Triangle Olfactometer
This olfactometer (originally designed by, IIT Research Institute) is used to measure the thresholds of odorants in accordance with ANSI/ASTM E679-97 (Standard Practice for Determination of Odor and Taste Thresholds by a Forced-Choice Ascending Concentration Series Methods of Limits, American
Society for Testing and Materials, Philadelphia, PA). The gaseous odorous sample is pumped into a capillary system by a
peristaltic pump fitted with good-grade Tygon tubing that produces a series of six dilutions, typically from 1700X to 7X. Higher dilutions can be obtained by prediluting the odorous sample. One sample containing diluted odorant and two samples of odor-free air are supplied in each set of three ports in a continuous flow dynamically from glass ports; the ports are arranged in a circle to avoid left/center/right preferences. Each set is mounted on flexible multiconduit tubing to permit
a limited rotation of the assembly by the panelist comparing the three ports. The panelist smells each set as long as needed to identify which of the samples contains the odorant. A decision must be made, even if it is a best guess, hence the name "forced choice". Proceeding from the weakest dilution to the strongest, the panelist signals a choice by pressing a button. Such a progression minimizes the effect of olfactory adaptation, which can cause a panelist's sensitivity to a weak odor to decrease temporarily if exposure begins at a strong level of the odor.

Dynamic Dilution Binary Scale Olfactometer (Butanol Wheel)
The butanol wheel measures the intensity of odorants in accordance with ASTM E544-99 [Standard Method for Measurement of Super-threshold Odor Intensity (Butanol Method) 1975, American Society for Testing and Materials, Philadelphia, PA]. The butanol wheel has eight ports located on a rotatable disk. Each port delivers dilutions of n-butanol that increase by a factor of 2 from the
previous port.

The panelist first smells the odorant being evaluated, then compares the intensity of the odorant to the n-butanol dilution at Port 1, the most dilute butanol level, and proceeds sequentially toward Port 8, the strongest.When the panelist finds a n-butanol dilution that corresponds to or exceeds the intensity of the sample odorant, the port number is recorded. If the panelist identifies the intensity as between two ports, the lower port number plus one-half is recorded.

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For more information:
2 South 631 Route 59, Suite B
Warrenville, Illinois 60555
630.393.9000
630.393.9111 (fax)