Odor Assessor Performance to Reference and Non-Reference Odorants

The European Standard test method for the determination of odor concentrations (EN13725:2003) is based on the standardization of the assessors (test subjects) with a known sensitivity to an accepted reference odorant, n-butanol. The assumption is made that the sensitivity for the reference will be a predictor for sensitivity to other substances, i.e. non-reference odorants, odorant mixtures, and environmental odors.Assessors from a commercial odor laboratory, certified to the EN13725 selection criteria, tested hydrogen sulfide as a non-reference odorant. Hydrogen sulfide was used as the non-reference odorant representing a common compound that is found in wastewater process odors and odors from various other industries, e.g. pulp and paper, landfill, agriculture. This paper analyzes the following:Comparison of individual assessor responses to n-butanol and hydrogen sulfide during a test session;Comparison of the odor panel results for n-butanol and hydrogen sulfide during a test session;Comparison of assessor performance testing with n-butanol and hydrogen sulfide; andComparison of panel performance testing with n-butanol and hydrogen sulfide.The first two objectives compare results obtained during any one test session through review of individual assessor responses and the panel average as a whole. The second two objectives will illustrate the repeatability of the individual assessors and the odor panel as a group by providing statistical evidence of parameters for accuracy and precision.EN13725 provides a framework for monitoring accuracy and precision of results in an olfactometry laboratory. Regular testing of the reference odorant n-butanol allows a laboratory to quantify these parameters. Periodic testing can also be performed on non-reference odor samples, e.g. hydrogen sulfide, to confirm these parameters as part of a comprehensive QA/QC program. This statistical information provides a user of odor testing results greater understanding of the meaning and application of these results.