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ASTM E1491-97(2002)

(Test Method)

Standard Test Method for Minimum Autoignition Temperature of Dust Clouds

Standard Test Method for Minimum Autoignition Temperature of Dust Clouds

SCOPE
1.1 This test method determines the minimum temperature at which a given dust cloud will autoignite when exposed to air heated in a furnace at local atmospheric pressure.
1.2 Data obtained from this test method provide a relative measure of dust cloud autoignition temperatures.
1.3 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 which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use.
1.4  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.

General Information

Status
Historical
Publication Date
09-Sep-1997
ICS
13.230 - Explosion protection
Technical Committee
E27 - Hazard Potential of Chemicals
Drafting Committee
E27.05 - Explosibility and Ignitability of Dust Clouds
Current Stage
Ref Project

Relations

Replaces
ASTM E1491-97 - Standard Test Method for Minimum Autoignition Temperature of Dust Clouds
Effective Date
10-Sep-1997
Replaced By
ASTM E1491-06 - Standard Test Method for Minimum Autoignition Temperature of Dust Clouds
Effective Date
01-Oct-2006
Referred By
ASTM E2021-15(2023) - Standard Test Method for Hot-Surface Ignition Temperature of Dust Layers
Effective Date
10-Sep-1997
Referred By
ASTM E1445-08(2015) - Standard Terminology Relating to Hazard Potential of Chemicals
Effective Date
10-Sep-1997

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ASTM E1491-97(2002) - Standard Test Method for Minimum Autoignition Temperature of Dust CloudsASTM E1491-97(2002) - Standard Test Method for Minimum Autoignition Temperature of Dust Clouds
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ASTM E1491-97(2002) - Standard Test Method for Minimum Autoignition Temperature of Dust Clouds
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E 1491 – 97 (Reapproved 2002)
Standard Test Method for
1
Minimum Autoignition Temperature of Dust Clouds
This standard is issued under the fixed designation E 1491; 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.
INTRODUCTION
This test method covers the determination of the minimum temperature at which a dust cloud will
autoignite.The dust cloud is exposed to air heated to various temperatures in a furnace. Ignition of the
cloud is indicated by visual observation of the flame. The chemical nature of the dust as well as its
concentration, particle size, moisture, and surface area affects the results.
1. Scope E 659 Test Method for Autoignition Temperature of Liquid
3
Chemicals
1.1 This test method covers the minimum temperature at
E 1226 Test Method for Pressure and Rate of Pressure Rise
which a given dust cloud will autoignite when exposed to air
3
for Combustible Dusts
heated in a furnace at local atmospheric pressure.
1.2 Data obtained from this test method provide a relative
3. Terminology
measure of dust cloud autoignition temperatures.
3.1 Definitions of Terms Specific to This Standard:
1.3 Thistestmethodshouldbeusedtomeasureanddescribe
3.1.1 dust concentration—the mass of dust divided by the
the properties of materials, products, or assemblies in response
internal volume of the test chamber.
to heat and flame under controlled laboratory conditions and
3.1.2 minimum autoignition temperature (MAIT)—themini-
shouldnotbeusedtodescribeorappraisethefirehazardorfire
mum temperature at which a dust cloud will self ignite under
risk of materials, products, or assemblies under actual fire
the specified conditions of test.
conditions.However,resultsofthistestmethodmaybeusedas
elements of a fire risk assessment which takes into account all
4. Summary of Test Method
of the factors which are pertinent to an assessment of the fire
4.1 The temperature of the furnace or oven is set at a
hazard of a particular end use.
predetermined value.
1.4 This standard does not purport to address all of the
4.2 Dust is blown into the heated furnace, which is at
safety concerns, if any, associated with its use. It is the
ambient pressure.
responsibility of the user of this standard to establish appro-
4.3 Ignitionisdeterminedbyvisualobservationoftheflame
priate safety and health practices and determine the applica-
exiting the furnace.
bility of regulatory limitations prior to use.
5. Significance and Use
2. Referenced Documents
5.1 This test method provides a procedure for performing
2.1 ASTM Standards:
laboratory tests to determine the minimum autoignition tem-
D 3173 Test Method for Moisture in theAnalysis Sample of
perature (MAIT) of a dust cloud.
2
Coal and Coke
5.2 The test data developed from this test method can be
D 3175 Test Method for Volatile Matter in the Analysis
used to limit the temperature to which a dust cloud is exposed
2
Sample of Coal and Coke
so as to prevent ignition of the cloud. Because of the short
duration of the test, the data obtained are most applicable to
1
This test method is under the jurisdiction ofASTM Committee E27 on Hazard industrialequipmentwheredustispresentasacloudforashort
Potential of Chemicalsand is the direct responsibility of Subcommittee E27.05on
time. Because of the small scale of the test and the possible
Explosibility and Ignitability of Dust Clouds.
Current edition approved Sept. 10, 1997. Published November 1997. Originally
published as E 1491 – 91. Last previous editiion E 1491 – 92.
2 3
Annual Book of ASTM Standards, Vol 05.05. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

---------------------- Page: 1 ----------------------
E 1491 – 97 (2002)
variation of the MAIT value with scale, the data obtained by 9. Sampling
this test method may not be directly applicable to all industrial
9.1 It is not practical to specify a single method of sampling
conditions.
dust for test purposes because the character of the material and
5.3 The MAIT data can also be used in conjunction with
its available form affect selection of the sampling procedure.
minimum spark ignition data to evaluate the hazards of
Generally accepted sampling procedures should be used as
5
grinding and impact sparks in the presence of dust clouds (1
described in STP 447A.
4
and 2).
9.2 Tests may be run on an as-received sample. However,
5.4 The test values obtained are specific to the sample
due to the possible accumulation of fines at some location in a
tested, the method used, and the test equipm
...

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5.1 This test method is applicable to dusts and powders, and provides a procedure for performing laboratory tests to evaluate hot-surface ignition temperatures of dust layers.  
5.2 The test data can be of value in determining safe operating conditions in industrial plants, mines, manufacturing processes, and locations of material usage and storage.  
5.3 Due to variation of ignition temperature with layer thickness, the test data at one thickness may not be applicable to all industrial situations (see Appendix X1). Tests at various layer thicknesses may provide a means for extrapolation to thicker layers, as listed in the following for pulverized Pittsburgh bituminous coal dust (2). Mathematical modeling of layer ignition at various layer thicknesses is described in Ref. (3).
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5.5 This test method for dust layers generally will give a lower ignition temperature than Test Method E1491, which is for dust clouds. The layer ignition temperature is determined while monitoring for periods of minutes to hours, while the dust cloud is only exposed to the furnace for a period of seconds.
Note 1: Much of the literature data for layer ignition is actually from a basket in a heated furnace (4), known as the modified Godbert-Greenwald furnace test. Other data are from nonstandardized hot plates (5-9).  
5.6 Additional information on the significance and use of this test method may be found in Ref. (10).
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1.1 This test method covers a laboratory procedure to determine the hot-surface ignition temperature of dust layers, that is, measuring the minimum temperature at which a dust layer will self-heat. The test consists of a dust layer heated on a hot plate.2,3  
1.2 Data obtained from this test method provide a relative measure of the hot-surface ignition temperature of a dust layer.  
1.3 This test method should be used to measure and describe the properties of materials in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard or fire hazard 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 that are pertinent to an assessment of the fire hazard risk of a particular end use product.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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1.6 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.

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ASTM E1515-14(2022)(Test Method)
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5.2 The MEC as measured by this test method provides a relative measure of the concentration of a dust cloud necessary for an explosion.  
5.3 Since the MEC as measured by this test method may vary with the uniformity of the dust dispersion, energy of the ignitor, and propagation criteria, the MEC should be considered a relative rather than absolute measurement.  
5.4 If too weak an ignition source is used, the measured MEC would be higher than the “true” value. This is an ignitability limit rather than a flammability limit, and the test could be described as “underdriven.” Ideally, the ignition energy is increased until the measured MEC is independent of ignition energy. However, at some point the ignition energy may become too strong for the size of the test chamber, and the system becomes “overdriven.” When the ignitor flame becomes too large relative to the chamber volume, a test could appear to result in an explosion, while it is actually just dust burning in the ignitor flame with no real propagation beyond the ignitor.  
5.5 The recommended ignition source for measuring the MEC of dusts in 20-L chambers is a 2500 or 5000 J pyrotechnic ignitor.4 Measuring the MEC at both ignition energies will provide information on the possible overdriving of the system.5 To evaluate the effect of possible overdriving in a 20-L chamber, comparison tests may also be made in a larger chamber, such as a 1 m3-chamber.  
5.6 If a dust ignites with a 5000 J ignitor but not with a 2500 J ignitor in a 20-L chamber, this may be an overdriven system.5 In this case, it is recommended that the dust be tested with a 10 000 J ignitor in a larger chamber, such as a 1 m3-chamber, to determine if it is actually explosible.  
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1.1 This test method covers the determination of the minimum concentration of a dust-air mixture that will propagate a deflagration in a near-spherical closed vessel of 20 L or greater volume.
Note 1: The minimum explosible concentration (MEC) is also referred to as the lower explosibility limit (LEL) or lean flammability limit (LFL).  
1.2 Data obtained from this test method provide a relative measure of the deflagration characteristics of dust clouds.  
1.3 This test method should be used to measure and describe the properties of materials 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 may be used as elements of a fire risk assessment that takes into account all of the factors that are pertinent to an assessment of the fire hazard of a particular end use.  
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1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  Specific precautionary statements are given in Section 8.  
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Standard Test Method for Explosibility of Dust Clouds

SIGNIFICANCE AND USE
5.1 This test method provides a procedure for performing laboratory tests to evaluate deflagration parameters of dusts.  
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Note 5: Ref (2) concluded that dusts with KSt values below 45 bar m/s when measured in a 20-L chamber with a 10 000-J ignitor, may not be explosible when tested in a 1-m3 chamber with a 10 000-J ignitor. Ref (2) and unpublished testing has also shown that in some cases the KSt values measured in the 20-L chamber can be lower than those measured in the 1-m3 chamber. Refs (1) and (3) found that for some dusts, it was necessary to use lower ignition energy in the 20-L chamber in order to match MEC or MIC test data in a 1-m3 chamber. If a dust has measurable (nonzero) Pmax and KSt values with a 5000 or 10 000-J ignitor when tested in a 20-L chamber but no measurable Pmax and ...
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1.1 Purpose. The purpose of this test method is to provide standard test methods for characterizing the “explosibility” of dust clouds in two ways, first by determining if a dust is “explosible,” meaning a cloud of dust dispersed in air is capable of propagating a deflagration, which could cause a flash fire or explosion; or, if explosible, determining the degree of “explosibility,” meaning the potential explosion hazard of a dust cloud as characterized by the dust explosibility parameters, maximum explosion pressure, Pmax; maximum rate of pressure rise, (dP/dt)max; and explosibility index, KSt.  
1.2 Limitations. Results obtained by the application of the methods of this standard pertain only to certain combustion characteristics of dispersed dust clouds. No inference should be drawn from such results relating to the combustion characteristics of dusts in other forms or conditions (for example, ignition temperature or spark ignition energy of dust clouds, ignition properties of dust layers on hot surfaces, ignition of bulk dust in heated environments, etc.)  
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1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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1.1 This test method is designed to determine the limiting oxygen concentration of a combustible dust dispersed in a mixture of air with an inert/nonflammable gas in a near-spherical closed vessel of 20 L or greater volume.  
1.2 Data obtained from this method provide a relative measure of the deflagration characteristics of dust clouds.  
1.3 This test method should be used to measure and describe the properties of materials 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 may be used as elements of a fire risk assessment that takes into account all of the factors that are pertinent to an assessment of the fire hazard of a particular end use.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 8.  
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Standard Test Method for Minimum Autoignition Temperature of Dust Clouds

SIGNIFICANCE AND USE
5.1 This test method provides a procedure for performing laboratory tests to determine the minimum autoignition temperature (MAIT) of a dust cloud.  
5.2 The test data developed from this test method can be used to limit the temperature to which a dust cloud is exposed so as to prevent ignition of the cloud. Because of the short duration of the test, the data obtained are most applicable to industrial equipment where dust is present as a cloud for a short time. Because of the small scale of the test and the possible variation of the MAIT value with scale, the data obtained by this test method may not be directly applicable to all industrial conditions.  
5.3 The MAIT data can also be used in conjunction with minimum spark ignition data to evaluate the hazards of grinding and impact sparks in the presence of dust clouds (1 and 2).3  
5.4 The test values obtained are specific to the sample tested, the method used, and the test equipment utilized. The test values are not to be considered intrinsic material constants, but may be used as a relative measure of the temperature at which a dust cloud self ignites.  
5.5 The test data are for cloud ignition. Dust in the form of a layer may ignite at significantly lower temperatures than the same dust in the form of a cloud (3). For liquid chemicals, see Test Method E659.
SCOPE
1.1 This test method covers the minimum temperature at which a given dust cloud will autoignite when exposed to air heated in a furnace at local atmospheric pressure.  
1.2 Data obtained from this test method provide a relative measure of dust cloud autoignition temperatures.  
1.3 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 which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 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.

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SIGNIFICANCE AND USE
5.1 This test method provides a procedure for performing laboratory tests to determine the minimum ignition energy of a dust cloud.
Note 1: For gases and vapors, see Test Method E582.  
5.2 The data developed by this test method may be used to assess the spark ignitibility of a dust cloud. Additional guidance on the significance of minimum ignition energy is in X1.1.  
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1.6 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.

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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.

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SIGNIFICANCE AND USE
5.1 This test method is applicable to dusts and powders, and provides a procedure for performing laboratory tests to evaluate hot-surface ignition temperatures of dust layers.  
5.2 The test data can be of value in determining safe operating conditions in industrial plants, mines, manufacturing processes, and locations of material usage and storage.  
5.3 Due to variation of ignition temperature with layer thickness, the test data at one thickness may not be applicable to all industrial situations (see Appendix X1). Tests at various layer thicknesses may provide a means for extrapolation to thicker layers, as listed in the following for pulverized Pittsburgh bituminous coal dust (2). Mathematical modeling of layer ignition at various layer thicknesses is described in Ref. (3).
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Hot-Surface Ignition Temperature, °C  
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210  
5.4 This hot plate test method allows for loss of heat from the top surface of the dust layer, and therefore generally gives a higher ignition temperature for a material than Test Method E771, which is a more adiabatic system.  
5.5 This test method for dust layers generally will give a lower ignition temperature than Test Method E1491, which is for dust clouds. The layer ignition temperature is determined while monitoring for periods of minutes to hours, while the dust cloud is only exposed to the furnace for a period of seconds.
Note 1: Much of the literature data for layer ignition is actually from a basket in a heated furnace (4), known as the modified Godbert-Greenwald furnace test. Other data are from nonstandardized hot plates (5-9).  
5.6 Additional information on the significance and use of this test method may be found in Ref. (10).
SCOPE
1.1 This test method covers a laboratory procedure to determine the hot-surface ignition temperature of dust layers, that is, measuring the minimum temperature at which a dust layer will self-heat. The test consists of a dust layer heated on a hot plate.2,3  
1.2 Data obtained from this test method provide a relative measure of the hot-surface ignition temperature of a dust layer.  
1.3 This test method should be used to measure and describe the properties of materials in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard or fire hazard 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 that are pertinent to an assessment of the fire hazard risk of a particular end use product.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 8.  
1.6 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.

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ASTM
ASTM E1515-14(2022)(Test Method)
Standard Test Method for Minimum Explosible Concentration of Combustible Dusts

SIGNIFICANCE AND USE
5.1 This test method provides a procedure for performing laboratory tests to evaluate relative deflagration parameters of dusts.  
5.2 The MEC as measured by this test method provides a relative measure of the concentration of a dust cloud necessary for an explosion.  
5.3 Since the MEC as measured by this test method may vary with the uniformity of the dust dispersion, energy of the ignitor, and propagation criteria, the MEC should be considered a relative rather than absolute measurement.  
5.4 If too weak an ignition source is used, the measured MEC would be higher than the “true” value. This is an ignitability limit rather than a flammability limit, and the test could be described as “underdriven.” Ideally, the ignition energy is increased until the measured MEC is independent of ignition energy. However, at some point the ignition energy may become too strong for the size of the test chamber, and the system becomes “overdriven.” When the ignitor flame becomes too large relative to the chamber volume, a test could appear to result in an explosion, while it is actually just dust burning in the ignitor flame with no real propagation beyond the ignitor.  
5.5 The recommended ignition source for measuring the MEC of dusts in 20-L chambers is a 2500 or 5000 J pyrotechnic ignitor.4 Measuring the MEC at both ignition energies will provide information on the possible overdriving of the system.5 To evaluate the effect of possible overdriving in a 20-L chamber, comparison tests may also be made in a larger chamber, such as a 1 m3-chamber.  
5.6 If a dust ignites with a 5000 J ignitor but not with a 2500 J ignitor in a 20-L chamber, this may be an overdriven system.5 In this case, it is recommended that the dust be tested with a 10 000 J ignitor in a larger chamber, such as a 1 m3-chamber, to determine if it is actually explosible.  
5.7 The values obtained by this test method are specific to the sample tested (particularly the particle size distribution) and the met...
SCOPE
1.1 This test method covers the determination of the minimum concentration of a dust-air mixture that will propagate a deflagration in a near-spherical closed vessel of 20 L or greater volume.
Note 1: The minimum explosible concentration (MEC) is also referred to as the lower explosibility limit (LEL) or lean flammability limit (LFL).  
1.2 Data obtained from this test method provide a relative measure of the deflagration characteristics of dust clouds.  
1.3 This test method should be used to measure and describe the properties of materials 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 may be used as elements of a fire risk assessment that takes into account all of the factors that are pertinent to an assessment of the fire hazard of a particular end use.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  Specific precautionary statements are given in Section 8.  
1.6 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.

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