ASTM E659-78(2000)
(Test Method)Standard Test Method for Autoignition Temperature of Liquid Chemicals
Standard Test Method for Autoignition Temperature of Liquid Chemicals
SCOPE
1.1 This test method covers the determination of hot- and cool-flame autoignition temperatures of a liquid chemical in air at atmospheric pressure in a uniformly heated vessel.
Note 1--Within certain limitations, this test method can also be used to determine the autoignition temperature of solid chemicals which readily melt and vaporize at temperatures below the test temperature.
1.2 This standard 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 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 .
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Designation:E659–78(Reapproved2000)
Standard Test Method for
Autoignition Temperature of Liquid Chemicals
This standard is issued under the fixed designation E 659; 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 is one of several methods developed by ASTM Committee E-27 for determining
the hazards of chemicals. It is designed to be used in conjunction with other tests to characterize the
hazard potential of the chemical under test.
1. Scope 3.2 autoignition, n—the ignition of a material commonly in
air as the result of heat liberation due to an exothermic
1.1 This test method covers the determination of hot- and
oxidation reaction in the absence of an external ignition source
cool-flameautoignitiontemperaturesofaliquidchemicalinair
such as a spark or flame.
at atmospheric pressure in a uniformly heated vessel.
3.3 autoignition temperature, n—the minimum temperature
NOTE 1—Withincertainlimitations,thistestmethodcanalsobeusedto
at which autoignition occurs under the specified conditions of
determine the autoignition temperature of solid chemicals which readily
test.
melt and vaporize at temperatures below the test temperature.
3.3.1 Autoignition temperature is also referred to as spon-
1.2 This standard should be used to measure and describe
taneous ignition temperature, self-ignition temperature, autog-
the properties of materials, products, or assemblies in response
enous ignition temperature, and by the acronymsAIT and SIT.
to heat and flame under controlled laboratory conditions and
Asdeterminedbythismethod,AITisthelowesttemperatureat
should not be used to describe or appraise the fire hazard or
which the substance will produce hot-flame ignition in air at
fire risk of materials, products, or assemblies under actual fire
atmospheric pressure without the aid of an external energy
conditions. However, results of this test may be used as
source such as spark or flame. It is the lowest temperature to
elements of a fire risk assessment which takes into account all
which a combustible mixture must be raised, so that the rate of
of the factors which are pertinent to an assessment of the fire
heat evolved by the exothermic oxidation reaction will over-
hazard of a particular end use.
balance the rate at which heat is lost to the surroundings and
cause ignition.
2. Referenced Documents
3.4 cool-flame, n—a faint, pale blue luminescence or flame
2.1 ASTM Standards:
occurring below the autoignition temperature (AIT).
D 2883 Test Method for Reaction Threshold Temperature
NOTE 2—Cool-flames occur in rich vapor-air mixtures of most hydro-
of Liquid and Solid Materials
carbons and oxygenated hydrocarbons. They are the first part of the
multistage ignition process.
3. Terminology
3.5 ignition delay time, n—the time lapse between applica-
3.1 Definitions:
tion of heat to a material and its ignition. It is the time in
3.1.1 ignition, n— the initiation of combustion.
seconds between insertion of the sample into the flask and
3.1.2 Ignition, which is subjective, is defined for this
ignition. It is maximum at the minimum autoignition tempera-
method as the appearance of a flame accompanied by a sharp
ture and also referred to as ignition lag.
rise in the temperature of the gas mixture.The determination is
made in total darkness because some flames, such as cool-
4. Summary of Test Method
flames, are observed with difficulty.
4.1 A small, metered sample of the product to be tested is
inserted into a uniformly heated 500-ml glass flask containing
air at a predetermined temperature. The contents of the flask
This test method is under the jurisdiction ofASTM Committee E27 on Hazard
are observed in a dark room for 10 min following insertion of
Potential of Chemicals,and is the direct responsibility of Subcommittee E27.04 on
the sample, or until autoignition occurs. Autoignition is evi-
Flammability and Ignitability of Liquid Chemicals.
denced by the sudden appearance of a flame inside the flask
Current edition approved Aug. 25, 1978. Published November 1978.
Annual Book of ASTM Standards, Vol 05.02. and by a sharp rise in the temperature of the gas mixture. The
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E659
lowest internal flask temperature (T) at which hot-flame 6. Apparatus
ignition occurs for a series of prescribed sample volumes is
6.1 Furnace—An electrically heated crucible furnace or
taken to be the hot-flame autoignition temperature (AIT) of the
fluidized sand bath of appropriate internal geometry and
chemical in air at atmospheric pressure. Ignition delay times
dimensions to contain the test flask and which will maintain a
(ignition time lags) are measured in order to determine the
uniform temperature within the flask shall be used. A furnace
ignition delay-ignition temperature relationship.
with a cylindrically shaped interior, 5 in. (12.7 cm) in inside
4.2 The temperatures at which cool-flame ignitions are
diameter, and 7 in. (17.8 cm) deep is minimal for this purpose.
observed or evidenced by small sharp rises of the gas mixture
It should be capable of attaining a temperature of 600°C or
temperature are also recorded along with the corresponding
higher.
ignition delay times. The lowest flask temperature at which
6.2 Temperature Controller—Atemperature control system,
cool-flame ignition occurs is taken to be the cool-flame
capable of controlling the temperature in the furnace to
autoignition temperature (CFT). Similarly, observations are
within6 1°C at temperatures up to 350°C, and to within 62°C
made of any nonluminous preflame reactions, as evidenced by
above 350°C, is required. Temperatures are monitored at the
a relatively gradual temperature rise which then falls off to the
bottom, side, and neck of the flask by means of three external
base temperature. The lowest flask temperature at which these
thermocouples. Heating adjustments are made when necessary
reactions are observed is the reaction threshold temperature
in order to maintain uniform temperature within the flask. If a
(RTT). controller is not available, temperature control may be
achieved by the use of suitable autotransformers or rheostats,
NOTE 3—The hot-flame autoignition, cool-flame autoignition, and re-
thermocouples, and a suitable potentiometer.
action threshold temperatures obtained by this test method approximate
6.3 Test Flask—The test flask shall be a commercial 500-ml
those temperatures obtained by Test Method D 2883 for hot-flame
borosilicate round-bottom, short-necked boiling flask.
reaction, cool-flame reaction, and reaction threshold, respectively.
6.3.1 The flask is closely wrapped in reflective metal foil,
5. Significance and Use
such as aluminum, to promote temperature uniformity, and is
suspended in the furnace so as to be completely enclosed with
5.1 Autoignition, by its very nature, is dependent on the
the top of the neck being inset below the top of the insulated
chemical and physical properties of the material and the
cover (see Fig. 1).
method and apparatus employed for its determination. The
6.3.2 The flask is suspended in the furnace or sand bath by
autoignition temperature by a given method does not necessar-
means of a thick insulating holder, the bottom of which is also
ily represent the minimum temperature at which a given
covered with reflective metal foil.
material will self-ignite in air.The volume of the vessel used is
6.4 Hypodermic Syringe—A 500 or 1000-µl hypodermic
particularly important since lower autoignition temperatures
syringe equipped with a 6-in., No. 26 or finer stainless steel
will be achieved in larger vessels. (See Appendix X2.) Vessel
needle, and calibrated in units of 10 µl should be used to inject
material can also be an important factor.
liquid samples into the heated flask. It is suggested that a
5.2 The temperatures determined by this test method are
needle with a right-angle bend be used so that the operator’s
those at which air oxidation leads to ignition. These tempera-
fingers can be kept away from the flask opening.
tures can be expected to vary with the test pressure and oxygen
6.5 Balance—A laboratory balance capable of weighing to
concentration.
the nearest 10 mg shall be used for preparing samples that are
5.3 Thistestmethodisnotdesignedforevaluatingmaterials
solid at room temperature. Sample weights will range from 10
which are capable of exothermic decomposition. For such
to 1000 mg.
materials, ignition is dependent upon the thermal and kinetic
6.6 Powder Funnel—A 60-mm filling funnel is used to aid
properties of the decomposition, the mass of the sample, and
the insertion of solid samples into the flask. It is suggested that
the heat transfer characteristics of the system.
a holder such as a small buret clamp be used so that the
5.4 This test method can be employed for solid chemicals
operator’s fingers can be kept away from the flask opening.
which melt and vaporize or which readily sublime at the test
6.7 Thermocouple—A fine Chromel-Alumel thermocouple
temperature. No condensed phase, liquid or solid, should be
(36 B and S gage) is used for measuring the gas temperature
present when ignition occurs.
(T) inside the flask. Position the tip of the thermocouple at the
5.5 This test method is not designed to measure the autoi-
center of the flask.Thermocouples should be calibrated against
gnition temperature of materials which are solids or liquids at
standard temperatures or a standard thermocouple, and should
thetesttemperature(forexample,wood,paper,cotton,plastics,
be rechecked frequently. Iron-constantan thermocouples are to
and high-boiling point chemicals). Such materials will ther-
be avoided because they may promote catalytic oxidation on
mally degrade in the flask and the accumulated degradation
the iron-oxide surface. External flask temperatures are mea-
products may ignite.
sured with a No. 20 B and S gage or finer thermocouple
mounted at the top ( t ), middle (t ), and bottom (t)ofthe
5.6 This test method was developed primarily for liquid
1 2 3
flask.
chemicals but has been employed to test readily vaporized
solids. Responsibility for extension of this method to solids of 6.8 Recording Potentiometer—A fast response (1 s or less
unknown thermal stability, boiling point, or degradation char-
forfullscalepentravel)variablerangeandvariablechartspeed
acteristics rests with the operator. recording potentiometer shall be used for recording the signal
E659
FIG. 1 Autoignition Temperature Apparatus
from the internal gas thermocouple (T). An x - y recorder has of a holder for the powder funnel will remove the hands from
been found suitable for this purpose.
the immediate vicinity of the flask opening.
6.9 Timer—A stop watch or electric timer (preferably foot-
7.2 It is recommended that the apparatus be installed in a
switch operated) calibrated in 0.1 or 0.2-s units shall be used to
fume hood or be equipped with an exhaust duct to prevent
determine the time lag before ignition (time interval between
exposure to potentially toxic combustion and decomposition
theinstantofsampleinsertionandthatofignitionasevidenced
products.All tests with toxic chemicals should involve the use
by the appearance of the flame). If visual ignition is difficult to
of adequate exhaust ventilation.
observe, the temperature - time recorder trace may be used to
7.3 Determinations normally should not be made on poten-
estimate the time lag.
tial or known explosive or propellant materials. Where such
6.10 Mirror—A6-in. mirror or other suitable size, mounted
AIT information is required, the determinations should be
above the flask so that the observer may see into the flask
made remotely behind a barricade.
without having to be directly over it.
6.11 Hot-Air Gun—A suitable hot-air gun may be used to
8. Procedure
purge the product gases after a reaction is completed and
before the next test. A temperature-controlled, hot-air guncan
8.1 Temperature Control—After the internal flask tempera-
reduce testing time if used to aid in achieving the desired flash
ture (T) has reached the desired temperature, adjust the
temperature between trials and upon insertion of clean test
temperature controller to maintain this temperature within the
flasks.
designated limits and allow the system to equilibrate.
8.2 Lighting—The lighting before sample insertion should
7. Safety Considerations
be very subdued. Extinguish the lights as the sample is
7.1 No explosion hazard is encountered in conducting the
inserted. Cool-flame tests are generally conducted in total
determination as outlined in Section 7. However, flames are
darkness. Eyes should be totally dark-adapted for optimum
occasionally emitted well above the top of the flask. Thus, the
observation of cool flames.
operatorshouldalwaysuseamirrorforobservationoftheflask
interior.Theuseofaright-anglesyringeand,forsolids,theuse 8.3 Sample Addition:
E659
8.3.1 Liquids—Inject 100 µl of the sample to be tested into 8.5.4 Use a new flask for tests on each product. Should the
the flask with the hypodermic syringe and quickly withdraw flask become visibly coated with residue before the completion
of tests for a given product, conduct the final series of tests
the syringe. Extinguish the lights as the sample is injected.
with a new flask.
8.3.2 Solids—Inserta100-mgsamplebypouringitfromthe
8.6 Autoignition—Autoignition is usually evidenced in
weighingvesselthroughthepowderfunnelwhichisinsertedin
these tests by hot flames of various colors, usually yellow, red,
the neck of the flask. Quickly withdraw the powder funnel and
or blue, but sometimes by cool flames that appear as faint
extinguish the lights.
bluish glows which are visible only in total darkness. Nor-
8.4 Time Measurement—Start the timer as the sample is
mally,thehotflamesproducesharptemperaturerisesofatleast
inserted into the flask, and also mark this on the recorder trace.
a few hundred degrees or more, whereas, the cool flames are
In most cases, the recorder trace of the interior thermocouple
accompanied by rises of less than 100°C. Cool flames gener-
will indicate the time of sample injection as a cooling spike.
ally occur at lower flask temperatures than hot flames but may
formoveranintermediatetemperaturerange,sothatthelowest
8.5 Observations and Subsequent Trials— Observe the
temperature at which any ignition occurs should be recorded.
inside of the test flask in total darkness by means of the mirror
Below these ignition temperatu
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