ASTM E681-98
(Test Method)Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapors and Gases)
Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapors and Gases)
SCOPE
1.1 This test method covers the determination of the lower and upper concentration limits of flammability of chemicals having sufficient vapor pressure to form flammable mixtures in air at atmospheric pressure at the test temperature. This test method may be used to determine these limits in the presence of inert dilution gases. No oxidant stronger than air should be used.
Note 1—The lower flammability limit and upper flammability limit are also referred to as the lower explosive limit (LEL) and the upper explosive limit (UEL), respectively.
1.2 This test method is based on electrical ignition and visual observations of flame propagation. Users may experience problems if the flames are difficult to observe (for example, irregular propagation or insufficient luminescence in the visible spectrum), if the test material requires large ignition energy, or if the material has large quenching distances.
1.3 provides a modified test method for materials (such as certain amines, halogenated materials, and the like) with large quenching distances which may be difficult to ignite.
1.4 In other situations where strong ignition sources (such as direct flame ignition) is considered credible, the use of a test method employing higher energy ignition source in a sufficiently large pressure chamber (analogous, for example, to the methods in Test Method E 2079 for measuring limiting oxygen concentration) may be more appropriate. In this case, expert advice may be necessary.
1.5 The flammability limits depend on the test temperature and pressure. This test method is limited to an initial pressure of the local ambient or less, with a practical lower pressure limit of approximately 13 kPa (100 mm Hg). The maximum practical operating temperature of this equipment is approximately 150°C (302°F).
1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are provided for information only.
1.7 This test method should be used to measure and describe the properties of materials, products, or assemblies in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard or fire risk of materials, products, or assemblies under actual fire conditions. However, results of this test method may be used as elements of a fire risk assessment that takes into account all of the factors pertinent to an assessment of the fire hazard of a particular end use.
1.8 This standard may involve hazardous materials, operations, and equipment. 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 and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 8.
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Designation: E 681 – 98
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
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 2. Referenced Documents
1.1 This test method covers the determination of the lower 2.1 ASTM Standards:
and upper concentration limits of flammability of chemicals E 171 Specification for Standard Atmospheres for Condi-
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having sufficient vapor pressure to form flammable mixtures in tioning and Testing Flexible Barrier Materials
air at one atmosphere pressure at the test temperature. This test E 582 Test Method for Minimum Ignition Energy and
method may be used to determine these limits in the presence Quenching Distance in Gaseous Mixtures
of inert dilution gases. No oxidant stronger than air should be E 1445 Terminology Relating to Hazardous Potential of
used. Care must be used when working with compounds Chemicals
containing oxygen. For chemicals that may be difficult to ignite E 1515 Test Method for Minimum Explosible Concentra-
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such as certain amines, halogenated materials, etc., refer to tion of Combustible Dusts
Annex A1.
3. Terminology
NOTE 1—The lower flammability limit and upper flammability limit are
3.1 Definitions:
also referred to as the lower explosive limit (LEL) and the upper explosive
3.1.1 lower limit of flammability or lower flammable limit
limit (UEL), respectively.
(LFL)—the minimum concentration of a combustible sub-
1.2 This test method is limited to an initial pressure of 101
stance that is capable of propagating a flame in a homogeneous
kPa (1 atm) or less, with a practical lower pressure limit of
mixture of the combustible and a gaseous oxidizer under the
approximately 13.3 kPa (100 mm Hg). The maximum practical
specified conditions of test.
operating temperature of this equipment is approximately
3.1.2 propagation of flame—as used in this test method, the
150°C (302°F).
upward and outward movement of the flame front from the
1.3 The values stated in SI units are to be regarded as the
ignition source to the vessel walls or at least to within 13 mm
standard. The values given in parentheses are provided for
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( ⁄2 in.) of the wall, which is determined by visual observation.
information only.
By outward, it is meant a flame front that has a horizontal
1.4 This test method should be used to measure and describe
component to the movement away from the ignition source.
the properties of materials, products, or assemblies in response
3.1.3 upper limit of flammability or upper flammable limit
to heat and flame under controlled laboratory conditions and
(UFL)—the maximum concentration of a combustible sub-
should not be used to describe or appraise the fire hazard or fire
stance that is capable of propagating a flame in a homogeneous
risk of materials, products, or assemblies under actual fire
mixture of the combustible and a gaseous oxidizer under the
conditions. However, results of this test method may be used as
specified conditions of test.
elements of a fire risk assessment that takes into account all of
the factors pertinent to an assessment of the fire hazard of a
4. Summary of Test Method
particular end use.
4.1 A uniform mixture of a gas or vapor with air is ignited
1.5 This standard may involve hazardous materials, opera-
in a closed vessel, and the upward and outward propagation of
tions, and equipment. This standard does not purport to
the flame away from the ignition source is noted by visual
address all of the safety concerns, if any, associated with its
observation. The concentration of the flammable component is
use. It is the responsibility of the user of this standard to
varied between trials until the composition that will just sustain
establish appropriate safety and health practices and deter-
propagation of the flame is determined.
mine the applicability of regulatory limitations prior to use.
Specific precautionary statements are given in Section 8
5. Significance and Use
5.1 The LFL and UFL of gases and vapors define the range
1 of flammable concentrations in air.
This test method is under the jurisdiction of ASTM Committee E-27 on Hazard
Potential of Chemicals and is the direct responsibility of Subcommittee E27.04 on
Flammability and Ignitability of Chemicals.
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Current edition approved April 10, 1998. Published December 1998. Originally Annual Book of ASTM Standards, Vol 15.09.
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published as E
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