INTRODUCTION
Community odors remain one of the top three complaints to air quality regulators and
government bodies around the U.S. and internationally. The majority of all air pollution
complaints are odor related.
Odors from a facility, such as a wastewater treatment plant, can affect the community. These
odors commonly lead to nuisance complaints. Estimating the effects of odors from a facility
often requires laboratory odor testing. In order to accomplish this testing, air samples from the
facility are collected and shipped overnight to an odor-testing laboratory. Engineers and
managers can use the odor test results to help in their decision making.
Odor testing in the laboratory is conducted to quantify an odorous air sample in terms of human
perception. During normal breathing, chemical molecules in the air pass by the olfactory
receptors in the top, back of the nasal cavity. The olfactory nerves signal the brain and create a
psychophysical response. For the general population the olfactory response to odors is normally
distributed. Therefore, a representative group of the population is called an odor panel (odor
assessors).
The statistical concepts that are used for odor testing are accepted internationally. The statistical
concepts are known as the "forced-choice method" and the "ascending concentration series
method". These methods are used when presenting a dilute odor sample to odor panelists for
determining detection and recognition thresholds. The device used to present the dilute odor
sample to odor panelists is called an "olfactometer".