ASTM E681-01

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Designation: E 681 – 01
Standard Test Method for
Concentration Limits of Flammability of Chemicals (Vapors
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and Gases)
This standard is issued under the fixed designation E 681; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 1.7 This test method should be used to measure and describe
the properties of materials, products, or assemblies in response
1.1 This test method covers the determination of the lower
to heat and flame under controlled laboratory conditions and
and upper concentration limits of flammability of chemicals
should not be used to describe or appraise the fire hazard or fire
having sufficient vapor pressure to form flammable mixtures in
risk of materials, products, or assemblies under actual fire
air at atmospheric pressure at the test temperature. This test
conditions. However, results of this test method may be used as
method may be used to determine these limits in the presence
elements of a fire risk assessment that takes into account all of
of inert dilution gases. No oxidant stronger than air should be
the factors pertinent to an assessment of the fire hazard of a
used.
particular end use.
NOTE 1—The lower flammability limit and upper flammability limit are
1.8 This standard may involve hazardous materials, opera-
also referred to as the lower explosive limit (LEL) and the upper explosive
tions, and equipment. This standard does not purport to
limit (UEL), respectively.
address all of the safety concerns, if any, associated with its
1.2 This test method is based on electrical ignition and
use. It is the responsibility of the user of this standard to
visual observations of flame propagation. Users may experi-
establish appropriate safety and health practices and deter-
ence problems if the flames are difficult to observe (for
mine the applicability of regulatory limitations prior to use.
example, irregular propagation or insufficient luminescence in
Specific precautionary statements are given in Section 8
the visible spectrum), if the test material requires large ignition
energy, or if the material has large quenching distances. 2. Referenced Documents
1.3 Annex A1 provides a modified test method for materials
2.1 ASTM Standards:
(such as certain amines, halogenated materials, and the like)
E 171 Specification for Standard Atmospheres for Condi-
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with large quenching distances which may be difficult to ignite.
tioning and Testing Flexible Barrier Materials
1.4 In other situations where strong ignition sources (such
E 582 Test Method for Minimum Ignition Energy and
as direct flame ignition) is considered credible, the use of a test
Quenching Distance in Gaseous Mixtures
method employing higher energy ignition source in a suffi-
E 1445 Terminology Relating to Hazardous Potential of
ciently large pressure chamber (analogous, for example, to the
Chemicals
methods in Test Method E 2079 for measuring limiting oxygen
E 1515 Test Method for Minimum Explosible Concentra-
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concentration) may be more appropriate. In this case, expert
tion of Combustible Dusts
advice may be necessary.
E 2079 Test Methods for Limiting Oxygen (Oxidant) Con-
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1.5 The flammability limits depend on the test temperature
centration in Gases and Vapors
and pressure. This test method is limited to an initial pressure
2.2 NFPA Standard:
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of the local ambient or less, with a practical lower pressure
NFPA 69 Standard on Explosion Prevention Systems
limit of approximately 13 kPa (100 mm Hg). The maximum
3. Terminology
practical operating temperature of this equipment is approxi-
mately 150°C (302°F).
3.1 Definitions:
1.6 The values stated in SI units are to be regarded as the
3.1.1 lower limit of flammability or lower flammable limit
standard. The values given in parentheses are provided for
(LFL)—the minimum concentration of a combustible sub-
information only.
stance that is capable of propagating a flame in a homogeneous
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This test method is under the jurisdiction of ASTM Committee E27 on Hazard
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Annual Book of ASTM Standards, Vol 15.09.
Potential of Chemicals and is the direct responsibility of Subcommittee E27.04 on
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Flammability and Ignitability of Chemicals. Annual Book of ASTM Standards, Vol 14.02.
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Current edition approved Oct. 10, 2001. Published February 2002. Originally Available from National Fire Protection Association, Batterymarch Park,
published as E 681 – 79. Last previous edition E 681 – 98. Quincy, MA 02269.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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E681–01
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