ASTM D6273-20

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
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: D6273 − 14 D6273 − 20
Standard Test MethodsMethod for
Natural Gas Odor Intensity
This standard is issued under the fixed designation D6273; 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 TheseThis test methods covermethod covers the procedures for determining the threshold detection level, readily detectable
level, and odor intensity of natural gas through the use of using instruments that dilute and mix the sampled natural gas with air.
The mixed gas stream is then sniffed by the operator for the purpose of determining the threshold detection level or the readily
detection level, or both, any of these parameters for odorant in thea natural gas stream.
1.2 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.
1.3 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:
D4150 Terminology Relating to Gaseous Fuels
D5287 Practice for Automatic Sampling of Gaseous Fuels
E253 Terminology Relating to Sensory Evaluation of Materials and Products
2.2 Other StandardsStandard:
49 CFR Part 192.625 Odorization of gasGas
3. Terminology
3.1 Definitions:
3.1.1 odorant, n—sulfur-bearing compound that gives natural gas a distinctive odor. For the purpose of these test methods, natural
gas odorants may be compounds that are present at the wellhead or commercial mixtures that are added to the gas stream, or both.
3.1.2 olfactory fatigue, n—desensitization of the sense of smell through either prolonged exposure or repeated exposure over a
short period of time to an odor, a mixture of odors, or series of odors.
3.1.3 sniff, vi—smell or snuff with short, audible inhalations.
TheseThis test methods aremethod is under the jurisdiction of ASTM Committee D03 on Gaseous Fuels and is the direct responsibility of Subcommittee D03.05 on
Determination of Special Constituents of Gaseous Fuels.
Current edition approved Jan. 1, 2014Nov. 1, 2020. Published February 2014November 2020. Originally approved in 1998. Last previous edition approved in 20082014
as D6273 – 08.D6273 – 14. DOI: 10.1520/D6273-14.10.1520/D6273-20.
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.
Available from Standardization Documents Order Desk, DODSSP, Bldg. 4, Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http://www.dodssp.daps.mil.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6273 − 20
3.1 For definitions of general terms used in D03 Gaseous Fuels standards, refer to Terminology D4150.
3.2 For definitions of common usage sensory evaluation of materials and products, refer to Terminology E253.
3.3 Definitions of Terms Specific to This Standard:
3.3.1 high pressure, n—for the purpose of thesethis test methods,method, high pressure refers to natural gas pressure greater than
the maximum inlet pressure specified by the manufacturer of the gas dilution apparatus.
3.3.2 intensity, n—the magnitude of odor perceived by the operator.
3.3.3 low pressure, n—for the purpose of thesethis test methods,method, low pressure refers to natural gas pressure less than or
equal to the maximum inlet pressure specified by the manufacturer of the gas dilution apparatus.
3.3.4 olfactory fatigue, n—desensitization of the sense of smell through either prolonged exposure or repeated exposure over a
short period of time to an odor, a mixture of odors, or a series of odors.
3.3.5 operator(s), n—the person(s) performing the testing described in these test methods. Because of the nature of the testing
described herein, the operator shall be qualified to perform this work (see this test method.5.2).
3.3.6 readily detectable level, n—the concentration of natural gas and odorant mixture in air at which the operator is able to detect
and identify natural gas odor.
3.3.7 sniff, v—smell or snuff with short, audible inhalations.
3.3.8 threshold detection level, n—the concentration of natural gas and odorant mixture in air at which the operator is barely able
to detect an odor.
3.3 For definitions of terms related to natural gas that are used in these test methods, refer to Practice D5287.
3.4 For definitions of terms related to olfactory testing that are used in these test methods, refer to Terminology E253.
4. Significance and Use
4.1 Federal regulations (49 CFR Part 192.625) state: “A combustible gas in a distribution line must contain a natural odorant or
be odorized so that at a concentration in air of one-fifth of the lower explosive limit, the gas is readily detectable by a person with
a normal sense of smell.” These regulations state further that “To assure the proper concentration of odorant with this section, each
operator must conduct periodic sampling of combustible gases using an instrument capable of determining the percentage of gas
in air at which the odor becomes readily detectable.” Additionally, a number of states have enacted legislation that requires natural
gas to be odorized so that it is detectable at concentrations less than one fifth of the lower explosive limit. See Note 1. While
regulations do not specify the exact method for determining compliance, it has been documented that compliance testing must be
olfactory in nature.
NOTE 1—For example, Massachusetts Section 192.625 MFS Standards requires that “. a concentration of fifteen hundredths of one percent gas in the
air is readily perceptible to the normal or average olfactory senses of a person.”
4.2 TheseThis test methods covermethod covers procedures to measure the odor level of natural gas by way of olfactory
determination. No direct correlation may be ascertained between thesethis test methodsmethod and those methods available or
under development that quantitatively measure the concentration of sulfur compounds in natural gas.
4.3 TheseThis test methods outlinemethod outlines general procedures to measure the odor detection levels of natural gas. It is
American Gas Association Operating Section Technical Note CAS-2-1-95, “ Natural “Natural Gas Odorization: Compliance with Federal Regulations.”
D6273 − 20
the responsibility of persons using thesethis test methodsmethod to develop and maintain equipment and specific operating
procedures to ensure public safety and compliance with all appropriate regulations.
5. Interferences and Precautions
5.1 The location to be tested should be sheltered from wind and isolated from Wind can dilute the apparatus exhaust; therefore,
protect the testing equipment from wind when sniffing. If possible, avoid testing near sources of interfering ambient odors such
as those from certain industrial plants and landfills. landfills, garbage bins, etc. The equipment and sampling lines used in testing
shall be clean and free of odor.
5.2 Operators shall be trained to perform odor testing of natural gas and in the proper use and care of test instrumentation. It is
preferred that operators should be nonsmokers, or, if smokers, they shall not smoke for at least 30 min before performing the test.
Additionally, operators shall not chew tobacco or gum or eat food of pungent taste or odor for at least 30 min before performing
the test. Operators should have no cold, allergies, or other physical conditions that would affect their sense of smell.
5.3 Prolonged use of the sense of smell may result in olfactory fatigue. Sufficient time shall be allotted between tests to ensure
that the tester’s sense of smell is not adversely affected by the previous test.
6. Apparatus
6.1 Gas Dilution Apparatus—This apparatus shall consist of a gas inlet control valve, a gas/air mixing chamber, a sample port for
sniffing the gas/air mixture, and a method to determine the relative concentration of the gas/air mixture. All components that come
in contact with natural gas shall be inert to odorant compounds.
6.2 Natural Gas Pressure Regulator(s)—This item may be required to lower the gas pressure at the sampling location to a level
that is safe for the gas dilution apparatus as specified by the manufacturer. This regulator may need to be a heated regulator if an
extremely large pressure drop is required, for example, when compressed natural gas or gas at transmission line pressure is to be
tested. More than one regulator may be required to perform this function satisfactorily.
6.2.1 The gas dilution apparatus shall never be subjected to natural gas pressures greater than that specified by the manufacturer.
Excessive natural gas pressure may result in instrument failure and cause an excessive amount of gas to vent out of the instrument.
6.2.2 The regulator shall be a heated regulator when Odorant compounds have a preference for liquid hydrocarbons when present.
When compressed natural gas (CNG) is to be tested or when it is anticipated that liquid hydrocarbons may condense from the gas
stream as a result of Joule-Thompson Expansion. Odorant compounds have a preference for liquid hydrocarbons when
present.Expansion, the regulator shall either:
6.2.2.1 Be a heated regulator, or
6.2.2.2 Require multiple pressure reductions to maintain a gas phase.
6.3 Sample Line—The sample line shall be clean and consist of material that is inert to natural gas odorant compounds. Sample
lines shall be tested periodically by performing a blank determinat
...