ASTM E544-18

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E544 − 10 E544 − 18
Standard PracticesPractice for
Referencing Suprathreshold Odor Intensity
This standard is issued under the fixed designation E544; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 These practices areThis practice is designed to outline a preferred means for referencing the odor intensities of a material
in the suprathreshold region.
1.2 The general objective is to reference the odor intensity rather than other odor properties of a sample.
1.3 These practices areThis practice is designed to reference the odor intensity on the ASTM Odor Intensity Referencing Scale
of any odorous material. This is done by a comparison of the odor intensity of the sample to the odor intensities of a series of
concentrations of thea reference odorant, which isfor example, 1-butanol (n-butanol).
1.4 The method by which the reference odorant vapors are to be presented for evaluation by the panelistsassessors is specified.
The manner by which the test sample is presented will depend on the nature of the sample, and is not defined herein.
1.5 Test sample presentation should be consistent with good standard practice (1, 2) and should be explicitly documented in
the test report.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. See Annex A1 for specific safety data.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1292 Test Method for Odor in Water
3. Terminology
3.1 ASTM odor intensity referencing scale—series of 1-butanol dilutions used to establish which concentration exhibits an odor
intensity matching that of the sample.
3.2 concentration—series of concentrations of 1-butanol in odorless air, nitrogen, or the water diluent, made to specific
reference dilutions which serve as the reference scale, volume basis, of 1-butanol diluted air or in water. In the latter case, the
temperature of the solution during the test should be reported.
3.2 dynamic scale—reference scale in which vapor dilutions are prepared by continuous mixing of vapors of 1-butanol with an
odorless gas, such as air, to yield constant dilutions of vapor in the gas. An example is presentation through an olfactometer.
3.4 panelists—individuals who compare the odor intensity of the sample to the reference scale. These individuals should be able
to do this with a consistency described in 5.5.
These practices areThis practice is under the jurisdiction of ASTM Committee E18 on Sensory Evaluation and are the direct responsibility of Subcommittee E18.04 on
Fundamentals of Sensory.
Current edition approved Nov. 1, 2010Oct. 1, 2018. Published December 2010October 2018. Originally approved in 1975. Last previous edition approved in 20042010
as E544 – 99 (2004).E544 – 10. DOI: 10.1520/E0544-10.10.1520/E0544-18.
The boldface numbers in parentheses refer to the list of references at the end of these recommended practices.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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3.5 perceived (sensory) odor intensity—intensity of an odor sensation which is independent of the knowledge of the odorant
concentration.
3.6 sample—material in any form exhibiting an odor that needs to be measured.
3.3 static scale—reference scale in which dilutions of 1-butanol in water are prepared in flasks or other suitable containers and
presented for odor intensity comparison from the flasks.comparison.
3.8 suprathreshold odor intensity—perceived (sensory) intensity of the odor in that intensity region in which the odor is clearly
experienced.
4. Summary of Practice
4.1 The reference odorant used to generate an odor intensity scale is 1-butanol (n-butanol). The reasons for its selection are
summarized in Appendix X1. A geometric progression scale with a ratio of 2 is recommended, that is, a scale in which each
reference dilution differs in its 1-butanol concentration from the preceding dilution by a factor of 2.
4.2 Two procedures, A and B, are described in these recommended practices. They differ in the method by which the diluted
1-butanol vapors are prepared.In this method, a series of known concentrations of 1-butanol is used.
NOTE 1—The relationships between the odor intensity of 1-butanol concentrations in air and in water have not been evaluated. Translation of Procedure
B data to the numerical values of Procedure A is not possible at this time.
4.2.1 In Procedure A, hereafter referred to as the dynamic scale method, a dynamic-dilution apparatus is used. This is equipped
with a series of sniffing ports from which constant concentrations of 1-butanol emerge at constant volumetric flow rates in air.
4.2.2 In Procedure B, hereafter referred to as the static-scale method, a series of Erlenmeyer flasks containing known
concentrations of 1-butanol in water is used.
4.3 The odor of the sample is matched, ignoring differences in odor quality, against the odor intensity reference scale of
1-butanol by a panel yielding at least eight independent judgments. Panelists panel. Assessors report that point in the reference
scale which, in their opinion, matches the odor intensity of the unknown.
4.4 The independent judgments of the panelistsassessors are averaged geometrically (see 7.46.3) with respect to the 1-butanol
concentrations of the indicated matching points. Results are reported as an odor intensity, in parts per million, of 1-butanol in air
(Procedure A)(dynamic method) or water (Procedure B)(static method) on the ASTM Odor Intensity Referencing Scale. When
water is used as a diluent, the temperature of the reference scale solutions during the test must be reported.
4.5 The odor intensity equivalent values which are obtained may then be used to compare the relative intensities of sample
groups. These values are reference values and are not related to the odor intensities by a simple proportionality coefficient (see
8.2Appendix X2).
5. Procedure A—Dynamic-Scale Method
5.1 Reagents:
5.1.1 1-butanol (n-butanol), the reference odorant, with required purity 99+ mol % by gas chromatography. Also shall be
chromatography and free of strong odorous impurities.
5.1.2 Diluent—Diluent: Nonodorous room or cylinder air.
5.1.2.1 For a “Static Method”, utilizing solutions in a suitable container, 1-butanol is prepared in an aqueous solution using
odor-free water.
NOTE 1—If diluent other than water is used, equivalent ppm (vol/vol) values will not exhibit matching odor intensities because of differences in
molecular weights, densities, and the activity coefficients of 1-butanol in different solvents. Use of other solvents is therefore not recommended.
5.1.2.2 For a “Dynamic Method”, utilizing an olfactometer, nonodorous room air, carbon filtered air, or cylinder air are
necessary.
5.2 Preparation of Static Scale:
5.2.1 Prepare solutions of 1-butanol in water, using pipets and volumetric flasks, following usual laboratory procedures for
solution preparation.
5.2.2 Procedure—Place the reference sniffing solutions into a suitable glass flask or jar. The volume of solution should be
selected to not fill more than ⁄4 of the sniffing container headspace. Between sniffing, cover the top of each container in order to
assure equilibration between the solution and the air head-space above it. The container should be gently swirled by each assessor
prior to each sniffing in order to assure equilibrium.
5.2.3 The temperature of the reference solutions during the test should be ambient and kept constant during the test.
5.2.4 The odor threshold of 1-butanol in water is 2.5 ppm at 21°C (3). The useful concentration range for the static scale is above
this value but does not extend to the solubility limit of 7.08 % of 30°C (70 800 ppm) (4). At concentrations close to the solubility
limit, excess 1-butanol may separate from the solution with temperature change. If this occurs the odor becomes equivalent to that
of pure 1-butanol.
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5.2.5 Considerable latitude as to the selection of concentrations is allowed. To go from the saturation point to the threshold
requires 16 steps, assuming that each succeeding mix is one half of the preceding concentration (70 800; 35 400; 17 000; 8850
ppm; etc.). Solutions stronger than 20 000 ppm of 1-butanol exhibit an odor that is too intense for most comparisons.
5.2.6 The most useful concentration range is approximately between 10 and 20 000 ppm, and may be covered by twelve flasks
containing 10 ppm in flask No. 1, 20 ppm in flask No. 2, etc. These flasks constitute the static scale.
5.2.7 The scale points are arranged systematically, in the order of increasing concentrations, and are numbered in ascending
integers, from 1 for the lowest concentration of 1-butanol.
5.3 Preparation of Dynamic Scale:
5.3.1 Prepare the 1-butanol airflow mixtures in an olfactometer apparatus as follows: Pass air over an expanded surface of
1-butanol in order to produce a saturated vapor at a known ambient temperature. Temperatures should be ambient in order to avoid
condensation in the airflow lines. Air becomes saturated (98+ %) at flow rates up to 60 mL/min when passed over a surface of
1-butanol that is 120 mm long by 10 mm wide in a 13-mm inside diameter glass tube which is held in a horizontal position.
Saturated vapor prepared by bubbling air through 1-butanol is less desirable since the bubbles burst at the surface and produce
droplets. In such methods of vapor generation, glass wool filter, operating at the same temperature as the 1-butanol liquid sample,
must be used to remove the droplets. Obtain concentrations of vapor below saturation by diluting the saturated vapor with
additional volumes of air.utilizing a known concentration of butanol from a prepared gas cylinder or by a headspace over liquid
butanol.
5.2.2 If air, such as pumped ambient air which contains water vapor is used, replace the 1-butanol in the saturation tube every
2 to 3 h; otherwise it will become diluted by the absorption of water which will lower the vapor pressure of 1-butanol, and will
result in a lower odorant concentration at the sniffing ports.
5.3.2 An adequate concentration range for most applications is between 5 will depend on olfactometer design, for example,
presentation air flow rate. For most applications a range between 200 ppb and 2000 ppm of 1-butanol in air. Above 2000 ppm, the
odor intensity is too strong for accurate judgment. Below 5 ppm, the odor is too close to the threshold limit for panelists to make
accurate judgments.air is most useful.
5.2.4 The temperature of 1-butanol in the saturation tube should be noted at the start and kept constant during the test. It should
be within the range of comfortable room temperatures.
5.2.5 The rate of dynamic delivery of air carrying diluted 1-butanol vapor from sniffing ports should be 160 6 20 mL/min from
a port with a cross-section of 400 to 500 mm , resulting in a nominal linear flow rate of 300 mm/min. A rate that is too slow allows
the stimulus to be diluted with increasing amounts of room air. A rate that is too fast creates a mechanical sensation in the nose
which complicates the odor intensity judgment.
5.2.6 An example of a dynamic dilution apparatus, called a dynamic olfactometer, is diagrammed in Fig. X1.1 and its operation
is explained, in Appendix X4.
5.4 Reference Concentrations:
5.4.1 This practice is intended to establish, on a continuous ppm 1-butanol scale, that ppm value concentration which best
corresponds in its odor intensity to the odor intensity of the sample. Since such a continuous scale is technically difficult, the one
designed a common olfactometer design consists of a series of discrete concentration points at sniffing ports continuously
delivering known concentrations of 1-butanol vapor in air.
5.4.2 A geometric progression scale of concentrations is used, in which each reference port differs in its 1-butanol concentration
from the preceding port by a factor of 2. It would have been desirable to select and always use the same ppm values for the same
ports, however, this would require very complex flow adjustment systems. Although the ppm values delivered by the scale ports
change with temperature, they remain in the same ratio to each other, and thus still permit the intensity equivalence point to be
easily found.
5.4.3 The scale points are arranged systematically, in the order of increasing concentrations, and are numbered in ascending
integers, from 1 for the lowest concentration of 1-butanol.
5.3.4 The matching points normally used are the scale points, or positions between the scale points, but can also be those points
beyond either end of the scale.
5.5 Test Room—The test room must be well-ventilated, essentially odor-free, and comfortable. In order to avoid bias, waiting
panelistsassessors should not observe or learn the judgments of the panelistassessor currently matching the odor intensity of the
sample to the scale (1, 2, 5, 6).
5.6 Odor Panel:
5.6.1 Number—The number of panelistsassessors should be eight or more, sufficient to permit elementaryproper statistical tests
on their judgments. A smaller number of panelistsminimum panel of six assessors is recommended. A small number of assessors
may be used with replicate judgments to increase the total to eight or more. number of responses. It is important when obtaining
replicate data that all bias is removed. Precautions such as separate sessions and recoding are recommended (1).
5.6.2 Selection—SpecialExtensive training is not needed but precautions must be taken in the selection of the panelistsassessors
(37, 8). An individual with insufficient sensitivity to detect the odor of 10 ppm of 1-butanol in airwater should not be a panelist.an
assessor. Also, some individuals have been observed to experience difficulty in matching odor intensities. Prospective
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panelistsassessors can be screened by having them repeatedly match the odor intensity of a known concentration of 1-butanol vapor
to the 1-butanol reference scale. Those whose standard deviation in repeated testing exceeds 1.5 scale steps should not be used in
the panel. Periodic retesting of panelists may be assessors is advisable.
5.7 Judgment Procedure:
5.7.1 PanelistsAssessors are instructed on the nature of the 1-butanol odor intensity reference scale. They are told that the ports
reference points are numbered beginning with No. 1, which represents the weakest odor and that the odors increase systematically
in intensity with increasing port identification numbers.
5.7.2 PanelistsAssessors are instructed to smell the unknown sample and then to smell the scale, beginning with its weakest
end,one or two references on the scale as they feel necessary. They should begin with weakest references, and match the unknown
to the scale, ignoring differences in the odor quality. They are permitted to check and recheck the unknown against the scale any
number of times and should not be hurried or biased by others in any manner.
5.7.3 Assessors should be instructed to take small, controlled sniffs of the test samples and the references. It is important for
assessors to be consistent in their sniffing technique when evaluating the samples and also sniffing the references for comparison.
5.7.4 PanelistsAssessors are advised that they may report one of the scale points as the best match, or elsethey may report that
the best match occurs between two adjacent points, for example, the unknown is stronger than scale point No. 7, but weaker than
scale point No. 8.
5.7.5 PanelistsAssessors should be advised that the odor may also be weaker than the weakest point of the scale, or stronger
than the strongest point of the scale.
5.7.6 When histhe judgment is within scale limits, the panelistassessor should make sure that the selected position is a good
match, that is, that the next lower concentration of 1-butanol indeed smells weaker than the unknown, and that the next higher
concentration indeed smells stronger.
5.7.7 PanelistsAssessors report the matching point in terms of the port identification number. When the best match is a position
between the scale points, such as between port Nos. 7 and 8, the half-number, 7.5, is may be used.
5.7.8 During repeated smelling of one or more samples or 1-butanol scale points, olfactory adaptation (fatigue) occurs,can
occur, rendering the sense of smell less sensitive. However, the relative position of the unknown with respect to the scale is not
unduly influenced unless the rates of adaptation to 1-butanol and to the sample are very different. The adaptation rate to 1-butanol
has been reported to be average when compared to other odorants sensitive (49). Therefore, the complication that may result from
differences in the adaptation rate to the unknown and to 1-butanol is minimized by selecting 1-butanol as the reference odorant.
5.7.9 Because of the olfactory adaptation discussed inthis olfactory adaptation, an assessor 5.6.7, a panelist may find that after
judging at higher odor intensity points on the scale, hethey may have difficulty in detecting odor at the lowest points of the scale.
A rest of 2 to 5 min will usually correct this effect.
5.7.10 PanelistsAssessors may differ in the amount of time required to render a judgment. The panelistassessor should be
allowed to proceed at a rate comfortable to him. rate. As many as six test stimuli can be handled by a panel of nine up to ten in
a 1-h1-hour session.
6. Procedure B—Static-Scale Method
6.1 The reference odorant is 1-butanol, (see 5.1.1). The diluent is distilled water that is odor-free.
NOTE 2—If diluent other than water is used, equivalent ppm (vol/vol) values will not exhibit matching odor intensities because of differences in
molecular weights, densities, and the activity coefficients of 1-butanol in different solvents. Use of other solvents is therefore not recommended.
6.2 Follow the procedures outlined in Section 5, except for 5.2.
6.3 Preparation of Static Scale:
6.3.1 Prepare solutions of 1-butanol in water, using pipets and volumetric flasks, following the usual laboratory procedures for
solution preparation.
6.3.2 Procedure—Place the reference sniffing solutions into standard 500-mL wide-mouth, conical Erlenmeyer flasks (see Test
Method D1292). The volume of solution should be 200 mL and should be replaced by new solutions after a maximum period of
2 h. Between sniffings, cover the top of each flask with aluminum foil in order to assure equilibration between the solution and
the air head-space above it. The flasks should be gently shaken by each panelist prior to each sniffing in order to assure equilibrium.
6.3.3 The temperature of the reference solutions during the test should be ambient, and should be noted and kept constant during
the test.
6.3.4 The odor threshold of 1-butanol in water is 2.5 ppm at 21°C (5). The useful concentration range for the static scale is above
this value but does not extend to the solubility limit of 7.08 % of 30°C (70 800 ppm) (6). At concentrations close to the solubility
limit, excess 1-butanol may separate from the solution with temperature change. If this occurs the odor becomes equivalent to that
of pure 1-butanol.
6.3.5 Considerable latitude as to the selection of concentrations is allowed. To go from the saturation point to the threshold
requires 16 flasks, assuming that each succeeding mix is one half of the preceding concentration (70 800, 35 400, 17 000, 8 850
ppm, etc.). Solutions stronger than 20 000 ppm of 1-butanol exhibit an odor that is too intense for most comparisons.
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6.3.6 The most useful concentration range is approximately between 10 and 20 000 ppm, and may be covered by twelve flasks
containing 10 ppm in flask No. 1, 20 ppm in flask No. 2, etc. These flasks constitute the static scale. The unknown sample is
matched to the static scale in the same manner as in the dynamic method (see 5.6).
6. Calculation
7.1 Procedure A—Table 1 lists 1-butanol concentrations, in parts per million, by volume, in vapor at equilibrium with pure,
liquid 1-butanol at different temperatures. Use this table to calculate the concentrations of 1-butanol in air (Procedure A).
7.1.1 Example 1—Assume that the temperature of 1-butanol was 20.3°C and the following linear interpolation of ppm values
is used:
65131@~7000 2 6513!~0.3/1!# 5 6659 ppm (1)
If air saturated with 1-butanol vapor at 20.3°C is further diluted with additional air to obtain a lower concentration, the value
of 6659 ppm is divided by the corresponding dilution factors to obtain the values for 1-butanol vapor concentrations at the
respective scale points.
7.1.2 For instance, if a 74-mL/min flow of air saturated with 1-butanol vapor is mixed with a 310-mL/min flow of nonodorous
air, the resulting 1-butanol vapor concentration would be the following:
~6659! @74/~741310!# 5 1283 ppm by volume (2)
6.1 Procedure B—For the static-scale method, the The values of parts-per-million concentrations of 1-butanol in water solutions
or air are known from the method of preparation (see 6.3.15.2 and 5.3).
6.2 When a panelistan assessor indicates that a position between two scale points is the best match, the concentration value for
this position is calculated as the geometricalgeometric mean of the concentrations at the two adjoining scale points. This applies
to both procedures. For example, if the 1-butanol concentrations at points No. 7 and No. 8 are 685658 and 1280 ppm, then the
concentration that would correspond to the intermediate position of 7.5 is found by the following logarithmic computation:
log 658 1log 1280
~ ! ~ !
log ppm for position 7.5 5 5 2.96 (1)
~ !
Tables of antilogarithms give The antilogarithm gives 918 ppm as the estimate for the 1-butanol concentration at the scale
position 7.5.
6.3 Averaging Panelists’Assessors’ Data—A geometric average of a group of panelists’assessors’ judgments is computed and
converted into an ASTM Odor Intensity Referencing Scale value, in parts per million of 1-butanol,1-butanol in water, in a manner
illustrated by the following example:
6.3.1 The odor of 3 % vol/vol of anethole dissolved in propylene glycol and a test sample prepared in 125-mL Erlenmeyer flasks
was evaluated for its odor intensity in comparison to that of a dynamically prepared scale at sniffing ports such as those described
in prepared static scale. Appendix X4. Nine panelistsassessors participated.
Matching 1-Butanol Concentration Data
Sniffing
Panelist Port No. ppm (vol/vol) log (ppm)
Assessor Port No. ppm (vol/vol) log (ppm)
1 5 165 2.22
2 6.5 452 2.66
3 7 658 2.88
4 6.5 452 2.66
5 7.5 919 2.96
6 7.5 919 2.96
7 7.5 919 2.96
8 6.5 452 2.66
9 5.5 226 2.35
6.3.2 The mean log in parts per million was equal to 2.701.2.694. The antilogarithm of 2.7012.694 is 502494 ppm of
1-butanol. This would be the best mean for the odor intensity match for the anethole solution.test sample. This result should be
reported in accordance with Section 78.
6.4 Standard Deviation—It is desirable to quote,provide the standard deviation of the mean log (ppm) value (26), for the
method of calculation used when reporting the results. For the example given in 7.4.26.3.1, the standard deviation of the mean log
(ppm) of 2.7012.694 is 60.27.
7. Report
7.1 Procedure A—Report the When the diluent is water and the static-scale method is used, report the result as follows:
7.1.1 The odor intensity of the sample is equivalent to ;lm__ ppm of 1-butanol (air) on in water, __ °C, in the ASTM Odor
Intensity Referencing Scale for Procedure A.Scale.
7.2 Procedure B—When the diluent is water and the static-scale a dynamic scale method is used, report the resultresults as
follows:
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7.2.1 The odor intensity of the sample is equivalent to _____ ppm of 1-butanol in water, __ °C, in (air) on the ASTM Odor
Intensity Referencing Scale for Procedure B.Scale.
7.3 Report the standard deviation of the result (see 7.56.4), if it is calculated. Also report the number of panelists that
participated.assessors that participated and if evaluations were replicated.
7.4 Values that are reported in this manner permit the comparison of odor intensity measurements for the same material to be
conducted in different locations by different panels, the comparison of odor intensities for samples which are not available at the
same time, and the reconstruction of a reported odor intensity for an unknown material in other laboratories.
8. Keywords
8.1 n-butanol; supra threshold odor intensity
ANNEX
(Mandatory Information)
A1. SAFETY DATA FOR 1-BUTANOL
A1.1 General—1-butanol is a common chemical used as a solvent for fats, waxes, resins, gums, and varnishes. It is also used in
the manufacture of lacquers, detergents, and rayon; in special cleaning applications; and as a fuel. It is not a listed carcinogen and
it does not cause lasting damage in case of accidental moderate overexposure. If ingested it is metabolized in a manner analogous
to that of ethanol. It is however an irritant for eyes, skin, and the respiratory tract. Prolonged inhalation or ingestion causes
dizziness and narcosis. Accordingly, contact times and concentrations of exposure should under no circumstances exceed those
required for the application of the method. Exposure to concentrations in excess of the ACGIHNIOSH Ceiling Value should be
avoided or, if deemed necessary, should be kept to a few seconds per exposure. Assessors who experience symptoms of uneasiness
during the test should be allowed the choice of not completing it.
A1.2 OSHA Requirement—The Occupational Safety and Health AuthorityAdministration enforces a workplace TLV (Threshold
Limit Value) of 100 ppm (300 mg/m ). This refers to an 8-h time-rated average. time weighted average (TWA). To determine
compliance in a workroom situation, air sampling should be conducted around the user at intervals during the work period, and
the average exposure should be calculated.
A1.3 ACGIHNIOSH Recommendation—The American Conference of Governmental Industrial Hygienists, Inc., 6500 Glenway
Ave., Bldg. D-7, Cincinnati, OH 45211-4438, recommends a TLV-C (TLV-Ceiling) National Institute for Occupational Safety and
Health has a Recommended Exposure Limit (REL) Ceiling value of 50 ppm (152 mg/m ). The user should obtain the relevant
documentation in full. A TLV-CAn REL-C is a momentary value; in a workroom situation, it signals the need to begin air sampling
in order to monitor any exposure above this level.
A1.4 Realistic Assessment—Determine the number of seconds an assessor is exposed to each concentration, then calculate the 8-h
time-rated average. time-weighted average (TWA). Example: 1 min at 1000 ppm, 2 min at 500 ppm, 4 min at 250 ppm, total 1
× 1000 + 2 × 500 + 4 × 250 = 3000 ppm × min. or 3000/60 × 8 = 6.25 ppm over 8 h. An assessor performing 4 such assessments
within the same 8-h period is exposed to an 8-h time-rated average of 4 × 6.25 = 25 ppm.
A1.5 Laboratory personnel should be provided training related to exposure precautions and proper handling of n-butanol. Safety
Data Sheets (SDS) for n-butanol should be available at all times.
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APPENDIXES
(Nonmandatory Information)
X1. SELECTION OF 1-BUTANOL AS THE REFERENCE ODORANT
X1.1 1-Butanol was selected as the reference odorant because:
X1.1.1 It is a common chemical and is readily available in 99+ mol % purity.
X1.1.2 It is non-toxic, except in multigram doses.
X1.1.3 It has good stability in the presence of air and water.
X1.1.4 Its odor is somewhat unrelated, so that its odor quality can be more easily ignored when comparing with other odors which
may have different qualities.
X1.1.5 The majority of people do not object to sniffing it frequently when doing odor-intensity referencing.
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X1.1.6 Its perceived-odor intensity changes rapidly with concentration, for example, the slope of the logarithmic odor intensity
versus the concentration plot is steep (see X3.2). Therefore, such a scale will cover a broad range of sensory intensities with a
reasonable number of scale points. Also, a well-noticeable odor-intensity difference occurs between two adjoining concentration-
scale points that differ in 1-butanol vapor content in air or 1-butanol concentration in water by a factor of 2.
X1.1.7 Since its odor threshold is relatively high (2 to 6 ppm (vol/vol) in air flowing at 100 to 200 mL/min), in air, a continuous
discharge of its vapors into the test room air does not result in a noticeable odor level in a normally ventilated room.
X1.1.8 Its concentration in air, down to the odor threshold concentration level, can be monitored with hydrogen-flame ionization
detectors without the need for preconcentration.
X2. PSYCHOPHYSICAL (SENSORY) INTERPRETATIONS
X2.1 It has been established (710, 811, 912, 1013) that the expression of odor intensity in terms of multiples of odor-threshold
concentration of an odorous material does not by itself properly reflect the actual sensory intensity of the odor presented. Odor
intensities increase with concentration at different rates for different odorants.
X2.2 Although category scales of words or numbers are valid for the evaluation of odor intensities, the absence of standards for
defining categories such as “slight,”“ moderate,”“slight,” “moderate,” etc., generate difficulties when comparing odor intensity
values obtained by category scaling by different groups of panelists.assessors.
...