February  2003  No. 280

Odor Measurement

At the Symposium on Air Quality Measurement Methods (San Francisco, November 2002) Charles McGinley of St. Croix Sensory, Inc., Lake Elmo, MN, talked about standardized odor measurement practices for air quality testing. McGinley said that community odors remain at the top of air pollution complaints to regulators and government bodies around the U.S. and internationally. Odor is measurable using objective, quantitative, standardized scientific methods in odor-testing laboratories. Point, area and volume emission sources can be sampled and tested for odor parameters such as odor concentration, intensity, persistence and descriptors.

Odor can also be measured and quantified directly in the ambient air using one of two standard practices by trained inspectors. The first method uses a standard odor intensity referencing scale made up of the standard odorant, n-butanol, to quantify odor intensity. The second method utilizes a field olfactometer, which dynamically dilutes the ambient air with carbon-filtered air in distinct dilution ratios. See the article on St. Croix Sensory's "New Olfactometer, the Nasal Ranger®" in the October 2002 newsletter (page 7).

McGinley described both U.S. and European odor measurement standard test methods. The Netherlands has played a very prominent role in advancing odor measurement standards. The results of a Dutch Inter-Laboratory study conducted from 1990-1992 led to the final Dutch standard released in 1995 and set the foundation for the development of a new European odor testing standard. A working group was formed within the Comité Européen de Normalisation (CEN) to develop a unified olfactometry standard. The first complete draft of the European standard was also released in 1995. In 1996, 19 laboratories from five countries participated in an Inter-laboratory Comparison of Olfactometry study.

The CEN olfactometry standard was released to the public at the end of 1999 as Proposed CEN standard 13725 (prEN 13725) "Air Quality–Determination of Odor Concentration by Dynamic Olfactometry." The final revision was sent to the CEN in 2001 for approval. Final approval will obligate all countries of the European Union to adopt the standard and withdraw any conflicting or redundant national standards. The new European standard has been adopted in Australia, New Zealand and much of the Pacific Rim. Therefore, EN 13725 will become the de facto International Standard for odor testing, according to McGinley.

In the U.S., the proliferation of large scale animal confinement facilities (i.e., feedlots) as well as the general trend of urban sprawl moving people closer to odorous industrial, wastewater treatment and agricultural facilities has created a resurgence in funding for odor related research. In 1995 the A&WMA's Odor Committee formed a subcommittee that developed "Guidelines for Odor Sampling and Measurement by Dynamic Olfactometry” that were submitted for review in August 2002 to the ASTM International Sensory Committee. In October 2002, the committee initiated a comprehensive review of ASTM E679-91 (the existing ASTM odor testing standard) and elements of the AWMA guidelines and the EN 13725 Standard. The objective of the ASTM review is to achieve the repeatability, reproducibility and accuracy in odor testing that was achieved by EN 13725. For McGinley's complete presentation, see the February Fact Finder for MO 030228.

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