Standardized Odor Measurement Practices for Air …

1 Standardized Odor MeasurementPractices for Air Quality TestingAuthored by:Charles M. McGinley, Croix Sensory, atAir and Waste Management AssociationSymposium on Air Quality MeasurementMethods and Technology - 2002 San Francisco, CA13-15 November, 2002St. Croix Sensory Inc. / McGinley Associates, Lake Elmo Ave. N., Box 313 Lake Elmo, MN 55042 +651-439-0177, 2002 1 2002 St. Croix Sensory, Odor Measurement Practices forAir Quality TestingCharles M. McGinley, Sensory, Inc., 3549 Lake Elmo Ave. N., PO Box 313 Lake Elmo, MN 55042 Tel: 651-439-0177 ext. 18, E-mail: air holds a mixture of odorous chemicals from everyday activities of industrialand commercial enterprises. From state to state and in communities across the UnitedStates odor issues are addressed by a variety of odor ordinances, regulations and air quality is compromised with odors, effective study, investigation, andenforcement requires that odors be measured using Standardized methods that aredependable, reproducible, objective, and , area and volume emission sources can be sampled and tested for odor parametersusing standard Practices published by the American Society of Testing and Materials(ASTM E679 and E544) and by the European Union (European Normalization Standard,EN 13725).

2 The most common odor parameter determined during odor testing is odorconcentration (odor strength). This determination is made using an instrument called an olfactometer. In the United States the standard followed for olfactometry is ASTMS tandard of Practice E679-91, Determination of Odor and Taste Threshold by a Forced-Choice Ascending Concentration Series Method of Limits. In 2002 this ASTM standardis under review to incorporate latest recommendations from the AWMA EE-6 OdorCommittee and elements from prEN 13725 Air Quality Determination of OdourConcentration by Dynamic Olfactometry . The 18 countries in the European Union arebound by the CEN/CENELEC International Regulations to implement this EuropeanStandard. The new European standard has been adopted in Australia, New Zealand, andmuch of the Pacific Rim. Therefore, EN 13725 will become the de facto InternationalStandard for odor/odour can also be measured and quantified directly in the ambient air using one of twostandard Practices .

3 ASTM E544-99, Standard Practice for Referencing SuprathresholdOdor Intensity , is used to measure and quantify ambient odor intensity using an OdorIntensity Referencing Scale (OIRS). An air pollution inspector, plant operator, orcommunity odor monitor can observe the ambient odor and compare it to the OIRS (aseries of concentrations of a reference odorant, n-butanol).A second standard method for measuring and quantifying odor in the ambient air utilizesa field olfactometer. The Standardized method ( Public Health Service Project GrantA-58-541) uses a portable odor detecting and measuring device known as a fieldolfactometer ( scentometer). The field olfactometer dynamically dilutes the ambientair with carbon-filtered air in distinct dilution ratios known as Dilution to Threshold dilution factors (D/T s), 2, 4, 7, 15, 2002 St. Croix Sensory, odors remain at the top of air pollution complaints to regulators andgovernment bodies around the and internationally.

4 Ambient air holds a mixture ofodorous chemicals from everyday activities of industrial and commercial state to state and in communities across the United States odor issues are addressedby a variety of odor ordinances, regulations and policies. When odors compromise airquality effective investigation and enforcement requires that odors be measured usingstandardized methods that are dependable, reproducible, objective, and quantification of odors is typically required for the following purposes:1. Monitoring for compliance Determination of compliance for permit Determination of baseline status for expansion Determination of specific odor sources during complaint Monitoring operations for management performance Comparison of operating Practices when evaluating Monitoring specific events or episodes for defensible, credible Comparison of odor mitigation measures during tests and Determination of an odor control system s performance for warranty Verification of estimated odor impacts from dispersion is measurable using objective, quantitative, Standardized scientific methods in odor-testing laboratories.

5 Point, area and volume emission sources can be sampled and testedfor odor parameters such as odor concentration, intensity, persistence, and can also be measured and quantified directly in the ambient air using one of twostandard Practices by trained inspectors. The first method uses a standard odor intensityreferencing scale (OIRS) made up of the standard odorant, n-butanol, to quantify odorintensity. The second method utilizes a field olfactometer, which dynamically dilutes theambient air with carbon-filtered air in distinct dilution ratios known as Dilution-to-Threshold dilution factors (D/T s).POINT, AREA & VOLUME ODOR SOURCE MEASUREMENTAn odorous air sample can be collected from a point emission source and from surfaceand volume emission sources. Whole-air samples for laboratory odor testing aretypically collected in 10-liter Tedlar gas sample bags for transport to the the early years of odor testing a syringe dilution technique measured odors in thelaboratory from samples collected at the odor source1.

6 That standard was ASTM D1391, Standard Test Method for Measurement of Odor in Atmospheres (dilution method) . The syringe dilution technique used a series of dilutions known as "dilution ratios". In3 2002 St. Croix Sensory, , ASTM E679-79, Standard Practice for Determination of Odor and TasteThresholds by a Forced-Choice Ascending Concentration Series Method of Limits waspublished2. The current edition of this odor-testing standard was approved on August 15,1991, and published in October 1991, as ASTM E679-91. This standard defines amethod of dynamically diluting the odor sample with an instrument called practicing ASTM E679-91 during an odor test, the odor panelist (assessor) sniffs adilute sample of the odor as it is discharged from the olfactometer as one of three samplepresentations (one presentation with the dilute odor and two with odor free air).

7 Theassessor sniffs all three of the presentations and must select the one of the three that isdifferent from the other two, even if they must guess. This statistical approach is called triangular forced-choice. The assessor declares to the test administrator if the selectionis a guess , a detection (the selection is different from the other two), or a recognition (the selection smells like something) as defined by ASTM assessor is then presented with the next set of three presentation choices, one ofwhich contains the diluted odor sample. However, this next set of three samples presentsthe odor at a higher concentration ( two times higher). The assessor continues toadditional levels of higher concentration (lower dilution) presentations following the triangular forced-choice procedure and the required designation of guess , detect , or recognition.

8 This statistical approach of increasing levels of sample presentation iscalled ascending concentration series. European Odor Testing StandardIn the 1980 s countries in Europe began developing standards of olfactometry. Some ofthese standards developed and published include:FranceAFNOR X-43-101, Method of the Measurement of the Odor of a GaseousEffluent, Bureau de Normalisation, Paris, France (drafted in 1981 & revised in 1986)GermanyVDI 3881, Parts 1-4, Richtlinien, Olfactometry, Odour ThresholdDetermination, Fundamentals. Verein Deutsche Ingenieure Verlag, Dusseldorf, Germany(drafted in 1980 & revised in 1989)NetherlandsNVN 2820, Provisional Standard: Air Quality. Sensory OdourMeasurement using an Olfactometer. Netherlands Normalization Institute, TheNetherlands (drafted in 1987 & issued in 1995)Various inter-laboratory studies as well as collaborative projects involving multiple odortesting laboratories in the 80 s showed that laboratory results still differed significantlyeven with these standards in development of a draft odor-testing standard in the Netherlands led to an Inter-Laboratory Comparison study organized in 19894.

9 N-butanol and hydrogen sulfide were4 2002 St. Croix Sensory, as standard odorants for the study. Through 1990 to 1992 the results of this DutchInter-Laboratory study led to the development of strict assessor performance the first year, the inter-laboratory repeatability was in the range of factors from3 to 20. An analysis of the data from this first year showed the majority of variabilitywas between assessors. Individual assessors were repeatable within a factor 3 to 5. Theresearchers found that the only way to meet agreed upon repeatability criteria was tocontrol the instrument sensor, the human assessors, by selecting assessors who were allsimilar in were set for assessor performance to the standard odorant n-butanol. Onlyassessors who met predetermined repeatability and accuracy criteria were allowed tocontinue as assessors. Over the next two years, these new criteria were implementedwithin each of the labs involved in the work of this inter-laboratory study led to the final Dutch standard released in 1995and set the foundation for the development of the new European odor testing working group was formed within the Committee European de Normalisation (CEN)Technical Committee 264 Air Quality to develop a unified olfactometry working group saw a need to help industry and regulators develop a consistent basisfor monitoring and testing odors, and, thus help determine the potential for odor was to be accomplished by developing a method that:1.

10 Improved consistency within each laboratory (repeatability);2. Achieved comparable results among laboratories (reproducibility); and3. Connect the results to a traceable reference material, n-butanol (accuracy)In order to achieve these goals, the committee focused on the following issues: samplingprocedures, sample containers, olfactometer construction and operation, the olfactometerand assessor interface, the odor testing room, methods of data processing, and assessorselection, training, and performanceThe first complete draft of the European olfactometry standard was released in in the spring and summer of 1996, nineteen laboratories from five countriesparticipated in an Inter-laboratory Comparison of Olfactometry (IOC) study. Thepurpose of this study was to validate the requirements, methods, and procedures outlinedin the draft. The conclusions of this study were5:1.