ASTM E502-21a

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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: E502 − 21 E502 − 21a
Standard Test Method for
Selection and Use of ASTM Standards for the Determination
of Flash Point of Chemicals by Closed Cup Methods
This standard is issued under the fixed designation E502; 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 This test method covers the determination of the flash point of liquid and solid chemical compounds flashing from below −10
to 370°C (16 to 700°F). The procedures and apparatus in Test Methods D56, D93, D3278, D3828, and D3941 are to be used.
Modification to these procedures are specified for tests on solids and viscous liquids. The significance of the results obtained is
discussed along with possible sources of error and factors that might cause interference.
1.2 Suggestions for adapting this procedure to mixtures of chemicals are included (see Appendix X2).
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 or assemblies under actual fire conditions. However, results of this test method may be used as elements of a fire risk
assessment that take 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. The values given in parentheses after SI units are provided for
information only and are not considered standard.
1.5 Warning—Mercury has been designated by the United States Environmental Protection Agency (EPA) and many state
agencies as a hazardous material that can cause central nervous system, kidney, and liver damage. Mercury, or its vapor, may be
hazardous to health and corrosive to materials. Caution should be taken when handling mercury and mercury containing products.
See the applicable product Material Safety Data Sheet (MSDS) for details and EPA’s website — http://www.epa.gov/mercury/
faq.htm — for additional information. Users should be aware that selling mercury or mercury-containing products, or both, into
your state may be prohibited by state law.
1.6 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. See also Section 8.
1.7 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.
This test method is under jurisdiction of ASTM Committee E27 on Hazard Potential of Chemicals and is the direct responsibility of Subcommittee E27.04 on
Flammability and Ignitability of Chemicals.
Current edition approved Feb. 15, 2021June 1, 2021. Published March 2021July 2021. Originally approved in 1984. Last previous edition approved in 20132021 as
E502 – 07 (2013).E502 – 21. DOI: 10.1520/E0502-21.10.1520/E0502-21A.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E502 − 21a
2. Referenced Documents
2.1 ASTM Standards:
D56 Test Method for Flash Point by Tag Closed Cup Tester
D92 Test Method for Flash and Fire Points by Cleveland Open Cup Tester
D93 Test Methods for Flash Point by Pensky-Martens Closed Cup Tester
D270 Methods of Sampling Petroleum and Petroleum Products (Withdrawn 1984)
D1310 Test Method for Flash Point and Fire Point of Liquids by Tag Open-Cup Apparatus
D3278 Test Methods for Flash Point of Liquids by Small Scale Closed-Cup Apparatus
D3828 Test Methods for Flash Point by Small Scale Closed Cup Tester
D3934 Test Method for Flash/No Flash Test—Equilibrium Method by a Closed-Cup Apparatus
D3941 Test Method for Flash Point by the Equilibrium Method With a Closed-Cup Apparatus
E681 Test Method for Concentration Limits of Flammability of Chemicals (Vapors and Gases)
E1232 Test Method for Temperature Limit of Flammability of Chemicals
3. Terminology
3.1 Definitions:
3.1.1 flash point, n—in flash point test methods, the lowest temperature of the test specimen, adjusted to account for variations in
atmospheric pressure from 101.3 kPa, at which application of an ignition source causes the vapors of the test sample to ignite under
specified conditions of test.
4. Summary of Test Method
4.1 The specimen is placed in a closed cup and, in the small scale method, equilibrated at a test temperature; in the Pensky-Martens
method, heated at a controlled rate with stirring; and in the tag method, also heated at a controlled rate but without stirring. A small
flame is directed into the vapor space of each cup at specified intervals, with simultaneous interruption of stirring in the
Pensky-Martens method, to determine whether a flash occurs or not. In Test Method D3941, the specimen is heated at a slower
rate than in the other controlled heating methods, maintaining a small temperature differential between bath and specimen.
5. Significance and Use
5.1 The flash point measures the response of the sample to heat and flame under controlled laboratory conditions. It is only one
of a number of properties that must be considered in assessing the overall flammability hazard of a material.
5.2 As a result of physical factors inherent in the apparatus and procedure, the closed cup flash point does not necessarily represent
the minimum temperature at which a material can evolve flammable vapors, and the absence of a flash point does not guarantee
nonflammability (see Appendix X1 and Appendix X2).
5.3 Flash point is used in shipping and safety regulations to define flammable and combustible materials. Test Methods D56, D93,
and D3278 are specified as test methods for determining the flash point of these materials.
5.4 If the process or handling conditions dictate the usage of a flammable material at temperatures ranging upward from 5 to 10°C
below the closed-cup flash point, then a flammable vapor might be present above the liquid. In such cases, it may be more
appropriate to use the temperature limit of flammability (as determined by Test Method E1232) instead of flash point.
5.5 Small scale For single component samples, small-scale methods involving equilibrium procedures and only one flame pass per
specimen are preferred.
5.6 For mixtures containing small concentrations of volatile components, special procedures are needed to minimize the loss of
volatiles, with consequent elevation of the flash point, while the sample is being heated. (See X2.5.)
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.
The last approved version of this historical standard is referenced on www.astm.org.
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5.7 In cases where errors caused by loss of volatiles, downwards flame direction and quenching are unacceptable, the “lower
temperature limit of flammability” can be determined instead using Test Method E1232. The temperature limit of flammability test
chamber is sufficiently large to overcome flame quenching effects in most cases of practical importance, thus, usually indicating
the presence of vapor-phase flammability if it does exist.
6. Interferences
6.1 Incorrect flash points can be obtained when testing chemicals corrosive to the materials of construction of the cup. (For
example, certain amines and acid chlorides react with the standard aluminum small scale cup causing erroneously low flash points,
perhaps due to hydrogen formation.) Cups employing alternative materials of construction, electroplating or plastic coating can
provide corrosion resistance. Results in non-standard cups, particularly in non-equilibrium tests, may differ slightly from those
obtained in this test method.
7. Apparatus
7.1 Tag Closed-Cup Tester, including thermometers, shall be as shown in Test Methods D56 and D3941.
7.2 Penksy-Martens Closed-Cup Tester, including thermometers, shall be as shown in Test Methods D93.
7.3 Small Scale Closed Tester, including thermometers, shall be as shown in Test Methods D3278 or D3828.
NOTE 1—Some automatic flash point testers may save testing time and permit the use of small samples. If automatic testers are used, the user must be
certain that all instructions for calibration and operation are followed to ensure that the results are equivalent to those obtained on the ASTM standard
equipment. For regulation purposes or in cases of dispute, the flash point as determined on the manual tester shall be the accepted value.
NOTE 2—ASTM thermometers 33C or 33F may be used in the tag tester instead of those specified in Test Method D56 when conducting tests at
temperatures below −10°C (14°F). Slight stem corrections may be necessary and care should be taken to avoid freezing the mercury in the thermometer
by cooling below −40°C (−40°F).
7.4 Shield, as described in Test Method D3941 or D1310.
8. Hazards
8.1 Toxicity of Chemical and Combustion Products:
8.1.1 Isolate or control operations on toxic or corrosive materials to prevent exposure to any personnel.
8.1.2 Since flash point tests are conducted in still air, the use of forced circulation for removal of toxic or nuisance fumes or
combustion products is restricted. However, a laboratory fume hood equipped with an exhaust damper that can be completely
closed provides an ideal location for maintaining draft-free conditions and provides the ability to readily exhaust dangerous vapors
and combustion products when necessary.
8.1.3 Use respiratory and splash protective devices as appropriate with toxic or corrosive materials. In most cases, approved
cartridge respirators are adequate respiratory protection for the concentrations normally encountered in flash-point testing. Certain
toxic or unusual materials, however, may require an air-supplied respirator and extreme cases may require complete protective
coverage such as an air-supplied plastic suit. (Two examples of the latter type of material are dimethyl sulfate and pure
mercaptans.) Tests on these highly toxic or obnoxious materials may also be conducted in completely isolated, closed systems, such
as glove boxes. In this case, procedures should ensure an uncontaminated air system in the box, and should prevent a buildup of
vapors from the material under test.
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8.2 Dry Ice Use:
8.2.1 Exercise care in the use of dry ice for sample and apparatus cooling. Avoid contact with dry ice to prevent frostbite. Glass
bottles or vials of chemicals should not be placed directly in dry ice or dry ice baths because of the possibility of breakage due
to thermal shock.
8.3 Tests of Explosives and Propellants:
8.3.1 Flash tests should not be conducted on potential or known explosive or propellant materials without complete prior
knowledge that burning will not result in propagation to an explosive decomposition. Properly barricaded or remotely operated
automatic testers should be used if precise flash points are needed.
8.4 Pyrophoric Materials:
8.4.1 Flash point apparatus is not applicable for the evaluation of pyrophoric materials and should not be used for this purpose.
9. Preparation of Sample
9.1 Obtain samples representative of the batch under test. Methods D270 can be used as a reference on sampling techniques. With
mixtures and with samples containing impurities, take care to avoid the loss of volatile components during sampling and handling
for testing. When heating viscous or solid materials for ease of pouring, samples must be held at temperatures below, or as close
as possible to, those specified in the various test methods. Discard samples from leaking or contaminated containers. Samples that
are hygroscopic should not be exposed to moisture or moist air.
9.2 Samples should not be stored in plastic (polyethylene, polypropylene, etc.) bottles, since volatile materials may diffuse through
the walls of the bottle.
10. Preparation of Apparatus
10.1 Support the appropriate flash-point tester on a level, steady work surface in a draft-free location. If a draft-free location is
not available, use a shield surrounding the tester on three sides. The shield should be approximately 460 mm (18 in.) wide and
610 mm (24 in.) high.
NOTE 3—An area capable of being partially darkened is advantageous since it aids in the detection of the relatively nonluminous flames sometimes
encountered in flash-point testing.
NOTE 4—Test Method D1310 gives a design for a draft shield suitable for standard flash-point testers.
11. Calibration
11.1 Check the condition and operation of the tag, Pensky-Martens, and small-scale testers as specified in Test Methods D56, D93,
D3278, or D3828, respectively.
12. Procedure
12.1 Follow the procedures outlined in Test Methods D56 or D3941 (tag closed cup), D3278 or D3828 (small-scale closed cup),
and D93 (Pensky-Martens closed cup), as is necessary. Certain explanatory notes and procedure modifications not contained in the
individual methods are given below. Occasionally, particularly near the temperature of the actual flash point, the application of the
test flame will cause a halo or test flame enlargement that should be ignored. In some cases this test flame enlargement will not
lead to a flash point on an increase in temperature.
−6 2 −6 2
12.2 For liquids with a viscosity less than 5.8 × 10 m /s (5.8 cSt) at 38°C (100°F), or 9.5 × 10 m /s (9.5 cSt) at 25°C (77°F),
observe the following:
−6 2 −6 2
NOTE 5—The first viscosity threshold point is stated either as “5.8 × 10 m /s (5.8 cSt) at 100°F (38°C)”, or as “5.5 × 10 m /s (5.5 cSt) at 40°C (104°F),
E502 − 21a
in different flash point test standards. The choice is indicative of only the unit system preferred by individual test standards. In practice the two forms
are considered equivalent.
12.2.1 If the flash point is below 93°C (200°F), use the small-scale (Test Method D3278 or D3828) or tag (Test Method D56)
apparatus and procedures.
12.2.2 If the flash point is 93°C (200°F) or above, use the small-scale (Test Method D3828) or Pensky-Martens (Test Methods
D93) apparatus and procedures.
NOTE 6—The electric heaters on some tag testers may be of insufficient capacity to maintain the specified heating rates when operating in the upper ranges
of this test method. Heat input can be increased slightly by using a variable transformer to increase the voltage slightly on the heaters. Insulation can be
applied to the exterior of the bath to reduce heat losses.
NOTE 7—With low temperature operation in the small scale methods, equilibrium may be difficult to maintain due to heating by natural convection. It,
therefore, will be necessary to cool the cup and sample below the anticipated flash point before specimen introduction (see Test Methods D3278).
NOTE 8—In the tag method (Test Method D56), natural warming rates sometimes exceed 1°C (2°F)/min. These rates can be reduced by insulating the
outside of the bath container. A laboratory refrigerated circulator may be used. One advantage of this system is that circulation of the refrigerant bath
with the system gradually warming up can serve as a control on heating rate.
NOTE 9—With low-temperature operation in the tag and small scale methods, difficulties can be created by the formation of frost on the surface of the
tester. If precise flash points are needed in the temperature range where frost conditions are encountered, tests can be conducted in a dry box or a room
of very low humidity. When ice formation on the lid and cover parts cannot be avoided, the results will be unreliable. Sticking of the slide due to ice
formation can be minimized by carefully lubricating the slide with a high vacuum silicone lubricant. Portions of the cover and slide in the vicinity of
the pilot flame and openings should be wiped free of frost just prior to the initial flame insertion at 5°C (10°F) below the flash point.
−6 2 −6 2
12.3 For liquids with a viscosity equal to or greater than 5.8 × 10 m /s (5.8 cSt) at 38°C (10
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