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ASTM E 681 Document Information:
Title
Standard Test Method for Concentration Limits of Flammability of Chemicals (Vapors and Gases)
ASTM International
Publication Date:
Jun 1, 2004
Scope:
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 (LFL) and upper flammability
limit (UFL) are sometimes
referred to as the lower explosive limit (LEL) and the upper explosive
limit (UEL), respectively.
However, since the terms LEL and UEL are also used to denote
concentrations other than the limits
defined in this test method, one must examine the definitions closely
when LEL and UEL values are
reported or used.
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.
Annex A1 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.
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.
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).
The values stated in SI units are to be regarded as the standard. The
values given in parentheses
are provided for information only.
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.
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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