Biomedical Engineering Reference
In-Depth Information
Fig. 4.12
Block diagram of field olfactometer air flow
varying diameter to permit a range of dilutions of odorous air to be sampled. An
observer begins by opening the port of smallest diameter to start with the largest
dilution (lowest concentration) of the odor [ 23 , 1 ]. An air flow diagram in field
Olfactometer is shown in Fig. 4.12 .
The method of calculating Dilution to Threshold (D/T) for a field Olfactometer is:
Dilution Factor ¼ Volume of Carbon Filtered Air = Volume of Odorous Air
¼ D = T
As successively larger ports are opened, the dilution of the odorous air
decreases and the odor concentration increases. When the evaluator can first detect
the odor, the odor threshold has been reached. Odor concentrations are expressed
as dilutions to threshold. The range of dilutions to threshold possible for the
Scentometer includes 1.5, 2, 7, 15, 31, 170, and 350.
Field olfactometry has the following key advantages over laboratory olfac-
tometry for measurement of ambient odors.
1. Lower method detection limit (most laboratory olfactometers have a method
detection limit of 5-10 dilutions);
2. Immediate results (Laboratory results can take 1-5 days to receive a report);
3. Eliminates concern for deterioration of odor in the sample bag; and
4. Low per sample cost.
Field olfactometry with a calibrated field olfactometer is a cost effective means
to measure odor strength. Facility operators, community inspectors, and neigh-
borhood citizens can confidently measure odor strength at specific locations
around a facility's property line and within the community when using a calibrated
field olfactometer.
4.8.4 Olfactometry
Olfactometers operate much like the Scentometer and the Nasal Ranger . The
primary differences are olfactometers that are not portable and an operator closely
controls sample delivery. Larger dilution to-threshold ranges are available.
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