ASTM G72/G72M-24

Standard Test Method for Autogenous Ignition Temperature of Liquids and Solids in a High-Pressure Oxygen-Enriched Environment

SIGNIFICANCE AND USE
4.1 Most organic liquids and solids will ignite in a pressurized oxidizing gas atmosphere if heated to a sufficiently high temperature and pressure. This procedure provides a numerical value for the temperature at the onset of ignition under carefully controlled conditions. Means for extrapolation from this idealized situation to the description, appraisal, or regulation of fire and explosion hazards in specific field situations, are not established. Ranking of the ignition temperatures of several materials in the standard apparatus is generally in conformity with field experience.  
4.2 The temperature at which material will ignite spontaneously (AIT) will vary greatly with the geometry of the test system and the rate of heating. To achieve good interlaboratory agreement of ignition temperatures, it is necessary to use equipment of approximately the dimensions described in the test method. It is also necessary to follow the described procedure as closely as possible.  
4.3 The decomposition and oxidation of some fully fluorinated materials releases so little energy that there is no clear-cut indication of ignition. Nor will there be a clear indication of ignition if a sample volatilizes, distilling to another part of the reaction vessel, before reaching ignition temperature.
SCOPE
1.1 This test method covers the determination of the temperature at which liquids and solids will spontaneously ignite. These materials must ignite without application of spark or flame in a high-pressure oxygen-enriched environment.  
1.2 This test method is intended for use at pressures of 2.1 MPa to 20.7 MPa [300 psi to 3000 psi]. The pressure used in the description of the method is 10.3 MPa [1500 psi], and is intended for applicability to high pressure conditions. The test method, as described, is for liquids or solids with ignition temperature in the range from 60 °C to 500 °C [140 °F to 932 °F].
Note 1: Test Method G72/G72M normally utilizes samples of approximately 0.20 ± 0.03-g mass, a starting pressure of 10.3 MPa [1500 psi] and a temperature ramp rate of 5 °C/min. However, Autogenous Ignition Temperatures (AIT) can also be obtained under other test conditions. Testing experience has shown that AIT testing of volatile liquids can be influenced by the sample pre-conditioning and the sample mass. This will be addressed in the standard as Special Case 1 in subsection 8.2.2. Testing experience has also shown that AIT testing of solid or non-volatile liquid materials at low pressures (that is, 8.2.3. Since the AIT of a material is dependent on the sample mass/configuration and test conditions, any departure from the standard conditions normally used for Test Method G72/G72M testing should be clearly indicated in the test report.  
1.3 This test method is for high-pressure pure oxygen. The test method may be used in atmospheres from 0.5 % to 100 % oxygen.  
1.4 An apparatus suitable for these requirements is described. This test method could be applied to higher pressures and materials of higher ignition temperature. If more severe requirements or other oxidizers than those described are desired, care must be taken in selecting an alternative safe apparatus capable of withstanding the conditions.  
1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
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.  
1.7 This international standard was developed in accordance with internationally recognize...

General Information

• Status: Published
• Publication Date: 31-Dec-2023
• ICS: 13.220.40 - Ignitability and burning behaviour of materials and products
• ICS: 13.230 - Explosion protection
• Technical Committee: G04 - Compatibility and Sensitivity of Materials in Oxygen Enriched Atmospheres
• Drafting Committee: G04.01 - Test Methods

Relations

• Replaces: ASTM G72/G72M-15 - Standard Test Method for Autogenous Ignition Temperature of Liquids and Solids in a High-Pressure Oxygen-Enriched Environment
• Effective Date: 01-Jan-2024

Overview

ASTM G72/G72M-24 is the internationally recognized standard test method for determining the autogenous ignition temperature (AIT) of liquids and solids in a high-pressure oxygen-enriched environment. This standard specifies procedures for identifying the minimum temperature at which materials spontaneously ignite under elevated pressures of oxygen, without the need for an external spark or flame. By providing consistent conditions and test configurations, ASTM G72/G72M-24 supports reliable laboratory determination of ignition temperatures, contributing to safety assessments where oxidizer-rich conditions may occur.

Key Topics

• Autogenous Ignition Temperature (AIT) Testing: Measures the lowest temperature at which a material will ignite spontaneously in a high-pressure oxygen environment.
• Applicability in Oxygen-Enriched Environments: Relevant for materials subject to pressures from 2.1 MPa to 20.7 MPa (300 psi to 3,000 psi) and oxygen concentrations from 0.5% up to 100%.
• Controlled Test Conditions: Standardized equipment, pressure, sample geometry, and heating rates are essential for reproducibility and comparability between laboratories.
• Sample Types: Test method applies to both organic liquids and solids, especially those with ignition temperatures between 60°C and 500°C (140°F to 932°F).
• Special Considerations: AIT measurements may be influenced by sample mass, configuration, heating rate, and system geometry, making adherence to standard procedure critical.
• Safety Precautions: Emphasizes equipment preparation, cleaning, and safe oxygen handling due to the high reactivity and risk of fire or explosion in oxygen-rich atmospheres.

Applications

ASTM G72/G72M-24 is utilized across multiple industries where high-pressure oxygen service and materials compatibility are concerns. Typical applications include:

• Oxygen System Design and Selection: Critical for selecting safe materials and equipment for use in aerospace, medical, chemical, and industrial gas sectors.
• Fire and Explosion Hazard Assessment: Used to evaluate the flammability risks of polymers, lubricants, and other organic materials in high-pressure environments.
• Regulatory Compliance and Safety: Supports manufacturers and facility operators in meeting safety regulations related to the storage, handling, and transport of oxygen and oxygen-enriched mixtures.
• Material Ranking: Provides a standardized basis for comparing the ignition characteristics of different materials, supporting informed decisions on material usage.

Related Standards

ASTM G72/G72M-24 references and works in conjunction with several other recognized standards and guidelines, including:

• ASTM D1193: Specification for Reagent Water
• ASTM E177: Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• ASTM G93: Guide for Cleanliness Levels and Cleaning Methods for Materials and Equipment Used in Oxygen-Enriched Environments
• CGA G-4 and G-4.1: Compressed Gas Association guidelines for oxygen use and safety
• Federal Specification BB-O-925: Standards for technical grade oxygen (gas and liquid)
• ASTM MNL 36: Manual for Safe Use of Oxygen and Oxygen Systems

Practical Value

Implementing ASTM G72/G72M-24 enables organizations to assess and mitigate flammability hazards under realistic, worst-case exposure scenarios in oxygen-rich and high-pressure service. The robust, repeatable methodology aids in:

• Material Qualification: Ensuring only validated materials are introduced into oxygen systems.
• Incident Prevention: Reducing the risk of catastrophic ignition events in critical infrastructure.
• Data Consistency: Facilitating the exchange of reliable safety data between manufacturers, regulators, and end users.
• Process Safety Management: Strengthening compliance with industry best practices and governmental regulations.

This standard is essential for professionals involved in the specification, safety evaluation, or operation of systems containing pressurized oxygen or oxygen-enriched atmospheres.

Standards Content (Sample)

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.
Designation: G72/G72M − 24
Standard Test Method for
Autogenous Ignition Temperature of Liquids and Solids in a
High-Pressure Oxygen-Enriched Environment
This standard is issued under the fixed designation G72/G72M; 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 1.5 The values stated in either SI units or inch-pound units
are to be regarded separately as standard. The values stated in
1.1 This test method covers the determination of the tem-
each system may not be exact equivalents; therefore, each
perature at which liquids and solids will spontaneously ignite.
system shall be used independently of the other. Combining
These materials must ignite without application of spark or
values from the two systems may result in non-conformance
flame in a high-pressure oxygen-enriched environment.
with the standard.
1.2 This test method is intended for use at pressures of
1.6 This standard does not purport to address all of the
2.1 MPa to 20.7 MPa [300 psi to 3000 psi]. The pressure used
safety concerns, if any, associated with its use. It is the
in the description of the method is 10.3 MPa [1500 psi], and is
responsibility of the user of this standard to establish appro-
intended for applicability to high pressure conditions. The test
priate safety, health, and environmental practices and deter-
method, as described, is for liquids or solids with ignition
mine the applicability of regulatory limitations prior to use.
temperature in the range from 60 °C to 500 °C [140 °F to
1.7 This international standard was developed in accor-
932 °F].
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
NOTE 1—Test Method G72/G72M normally utilizes samples of ap-
proximately 0.20 6 0.03-g mass, a starting pressure of 10.3 MPa
Development of International Standards, Guides and Recom-
[1500 psi] and a temperature ramp rate of 5 °C ⁄min. However, Autog-
mendations issued by the World Trade Organization Technical
enous Ignition Temperatures (AIT) can also be obtained under other test
Barriers to Trade (TBT) Committee.
conditions. Testing experience has shown that AIT testing of volatile
liquids can be influenced by the sample pre-conditioning and the sample
2. Referenced Documents
mass. This will be addressed in the standard as Special Case 1 in
subsection 8.2.2. Testing experience has also shown that AIT testing of
2.1 ASTM Standards:
solid or non-volatile liquid materials at low pressures (that is, < 2.1 MPa)
D1193 Specification for Reagent Water
can be significantly influenced by the sample mass and the temperature
E177 Practice for Use of the Terms Precision and Bias in
ramp rate. This will be addressed in the standard as Special Case 2, in
ASTM Test Methods
subsection 8.2.3. Since the AIT of a material is dependent on the sample
mass/configuration and test conditions, any departure from the standard E691 Practice for Conducting an Interlaboratory Study to
conditions normally used for Test Method G72/G72M testing should be
Determine the Precision of a Test Method
clearly indicated in the test report.
G93 Guide for Cleanliness Levels and Cleaning Methods for
1.3 This test method is for high-pressure pure oxygen. The
Materials and Equipment Used in Oxygen-Enriched En-
test method may be used in atmospheres from 0.5 % to 100 %
vironments
oxygen.
2.2 Federal Specification:
BB-O-925 Oxygen, Technical, Gas and Liquid
1.4 An apparatus suitable for these requirements is de-
2.3 Other Documents:
scribed. This test method could be applied to higher pressures
MNL 36 Safe Use of Oxygen and Oxygen Systems: Guide-
and materials of higher ignition temperature. If more severe
lines for Oxygen System Design, Materials, Selection,
requirements or other oxidizers than those described are
Operations, Storage, and Transportation
desired, care must be taken in selecting an alternative safe
apparatus capable of withstanding the conditions.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
This test method is under the jurisdiction of ASTM Committee G04 on the ASTM website.
Compatibility and Sensitivity of Materials in Oxygen Enriched Atmospheres and is Available from U.S. Government Printing Office Superintendent of Documents,
the direct responsibility of Subcommittee G04.01 on Test Methods. 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
Current edition approved Jan. 1, 2024. Published February 2024. Originally www.access.gpo.gov.
approved in 1982. Last previous edition approved in 2015 as G72/G72M – 15. DOI: ASTM Manual Series, Available from ASTM International, 100 Barr Harbor
10.1520/G0072_G0072M-24. Drive, W. Conshohocken, PA 19428.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G72/G72M − 24
Compressed Gas Association Booklets G-1 and G-4.1 tion of fire and explosion hazards in specific field situations,
are not established. Ranking of the ignition temperatures of
3. Summary of Test Method
several materials in the standard apparatus is generally in
conformity with field experience.
3.1 This autogenous ignition temperature test method is
designed to expose solid or liquid sample material to increasing
4.2 The temperature at which material will ignite spontane-
temperature in a high-pressure reaction vessel. The reaction
ously (AIT) will vary greatly with the geometry of the test
vessel (bomb), including a sample holding assembly, is pres-
system and the rate of heating. To achieve good interlaboratory
surized with the oxygen-enriched environment. The bomb is
agreement of ignition temperatures, it is necessary to use
heated in an electric furnace at a predetermined rate. The
equipment of approximately the dimensions described in the
temperature of the sample-holding assembly is monitored as a
test method. It is also necessary to follow the described
function of time by means of a thermocouple and recording
procedure as closely as possible.
potentiometer.
4.3 The decomposition and oxidation of some fully fluori-
3.2 The minimum temperature required to cause the sample
nated materials releases so little energy that there is no
to ignite spontaneously is determined at any selected system
clear-cut indication of ignition. Nor will there be a clear
pressure. The point at which spontaneous ignition occurs is
indication of ignition if a sample volatilizes, distilling to
denoted by a sudden rise in temperature and the destruction of
another part of the reaction vessel, before reaching ignition
the sample. The amount of rise in temperature is related to the
temperature.
sample size. A sample size is selected to prevent damage to the
equipment caused by exceeding safe system pressure or
5. Apparatus
temperature limits because of the temperature rise.
5.1 Suitable components shall be assembled so that the
3.3 The system is pressurized to the desired test pressure at
specified reaction vessel (bomb), including sample-holding
the start of the test. During the test as the temperature is
assembly, can be charged with oxygen and heated. The
increased, the pressure increases. No effort is made to control
assembly shall provide a means of recording time and tem-
the pressure during the test. It is monitored only so that the
perature at which ignition occurs. A suitable assembly is
pressure does not exceed a safe limit for the test equipment.
illustrated in Fig. 1.
4. Significance and Use
5.2 Cylinder Oxygen, conforming to Federal Specification
BB-O-925, Type I or oxygen of 99.5 % minimum purity.
4.1 Most organic liquids and solids will ignite in a pressur-
Oxygen of higher purity may be used if desired.
ized oxidizing gas atmosphere if heated to a sufficiently high
temperature and pressure. This procedure provides a numerical
5.3 Line Filter, sintered tin-bronze, 5-μm porosity, maxi-
value for the temperature at the onset of ignition under
mum pressure 206.8 MPa [30 000 psi], for 6.35-mm [ ⁄4-in.]
carefully controlled conditions. Means for extrapolation from
high-pressure tubing with a 3.18-mm [ ⁄8-in.] port.
this idealized situation to the description, appraisal, or regula-
5 Catalog No. 49-14405 available from Superpressure, Inc., Silver Spring, Md.
Available from Compressed Gas Association (CGA), 4221 Walney Rd., 5th
20910 or equivalent has been found satisfactory.
Floor, Chantilly, VA 20151-2923, http://www.cganet.com.
FIG. 1 AIT Equipment Assembly
G72/G72M − 24
FIG. 2 Sample Holding Assembly
5.4 Compressor Pumps, diaphragm-type, air-driven, [ ⁄4 in.] high-pressure, angle type with 48.3 MPa [7000 psi] at
10 000 psi output pressure. 22.2 °C [72 °F] rupture disks.
5.5 Valves, 6.35 mm [ ⁄4 in.] high-pressure, 206.8 MPa
5.10 Reaction Vessel (Bomb)—A suitable reaction vessel for
[30 000 psi] working pressure, nonrotating stem valves.
the test method is cylindrical, approximately 65 mm [2 ⁄16 in.]
1 in outside diameter and 298 mm [11 ⁄4 in.] long and weighs
5.6 Pressure Gage, 20.7 MPa [3000 psi], 216 mm [8 ⁄2 in.],
9.75 kg [21 ⁄2 lb]. The vessel is bored from a solid forging of
0.1 % F.S. Accuracy.
AISI 316SS [8 ⁄4 in.] depth, with a volume equal to approxi-
5.7 Connecting Tubing, Type 316 stainless steel, 6.35 mm
mately 110 mL. The maximum working pressure at 427 °C
[ ⁄4 in.] high-pressure tubing, 448.1 MPa [65 000 psi] pressure
[800 °F] is 82.7 MPa [12 000 psi].
rating at 37.8 °C [100 °F].
5.11 Thermocouple Assembly—A Chromel-Alumel thermo-
5.8 High-Pressure Tees, Type 316 stainless steel with gland
couple with suitable high-pressure fittings for the reaction
nuts and sleeves of Type 416 stainless steel, 6.35 mm [ ⁄4 in.]
vessel with a 203-mm [8-in.] thermocouple to extend into the
high-pressure. All connection fittings shall be of cold-drawn
reaction chamber.
Type 316 stainless steel, 413.7 MPa [60 000 psi] maximum
5.12 Heating Jacket—A 230-V, 1000-W single-phase heat-
pressure, tubing size 6.35 mm [ ⁄4 in.] high-pressure and
ing jacket designed to fit the reaction vessel should be used.
14.3-mm [ ⁄16-in.] insertion depth.
5.9 Pressure-Relief Blowout with Rupture Discs, pressure- 5.13 Recorder, 0 °C to 1000 °C [0 °F to 2000 °F]—A strip
relief blow-out assembly, Type 316 stainless steel, 6.35 mm chart recording pyrometer in the temperature range for the test
G72/G72M − 24
6.3 Deionized or Distilled Water, conforming to Specifica-
tion D1193, Type IV.
6.4 Oxygen, conforming to Federal Specification BB-0-925,
Type I or oxygen of 99.5 % purity. Oxygen of higher purity
may be used if desired.
7. Safety Precautions
7.1 Nitric Acid:
Warning! Harmful by inhalation, skin contact, and if swal-
lowed.
Although not combustible, is a powerful oxidizing agent,
which may cause combustible materials to ignite.
Wear appropriate NIOSH-approved respirator, chemical re-
sistant gloves (butyl rubber), safety goggles.
7.2 Sodium Hydroxide:
Warning! Harmful by inhalation, skin contact, and if swal-
lowed.
Use adequate ventilation.
Wear face shield, lab coat, rubber apron.
Store away from strong acids
7.3 Oxygen:
Warning! Oxygen vigorously accelerates combustion.
Keep oil and grease away. Do not use oil or grease on
regulators, gages, or control equipment.
FIG. 3 Inner Reaction Vessel Stopper
Use only with equipment conditioned for oxygen service by
carefully cleaning to remove oil, grease, and other combus-
tibles.
method should be used. The scale must be such that a sudden
Keep combustibles away from oxygen and eliminate ignition
change of 20 °C [36 °F] or more in temperature in the reaction
sources.
vessel is clearly indicated.
Keep surfaces clean to prevent ignition or explosion, or both,
5.14 Inner Reaction Vessel—A borosilicate glass test tube
on contact with oxygen.
15 mm by 125 mm.
Always use a pressure regulator. Release regulator tension
before opening cylinder valve.
5.15 Sample Holder—A borosilicate glass culture tube 10
by 75 mm. All equipment and containers used must be suitable and
recommended for oxygen service.
5.16 Wire Support, fashioned from 20 % Chromuim, 80 %
Never attempt to transfer oxygen from cylinder in which it is
Nickel, No. 21 AWG wire. Several turns of wire are wound on
received to any other cylinder. Do not mix gases in cylinders.
a mandrel of sufficient size so that the resulting spring-like
Do not drop cylinder. Make sure cylinder is secure at all
structure fits the inner reaction vessel snugly. A loop of wire is
times.
bent to hold the vessel at the proper height, positioning the
Keep cylinder closed when not in use.
thermocouple assembly in the mouth of the sample holder (Fig.
S
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
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: G72/G72M − 15 G72/G72M − 24
Standard Test Method for
Autogenous Ignition Temperature of Liquids and Solids in a
High-Pressure Oxygen-Enriched Environment
This standard is issued under the fixed designation G72/G72M; 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 temperature at which liquids and solids will spontaneously ignite. These
materials must ignite without application of spark or flame in a high-pressure oxygen-enriched environment.
1.2 This test method is intended for use at pressures of 2.1 to 20.7 MPa [300 to 3000 psi]. 2.1 MPa to 20.7 MPa [300 psi to
3000 psi]. The pressure used in the description of the method is 10.3 MPa [1500 psi], 10.3 MPa [1500 psi], and is intended for
applicability to high pressure conditions. The test method, as described, is for liquids or solids with ignition temperature in the
range from 6060 °C to 500 °C [140[140 °F to 932 °F].
NOTE 1—Test Method G72/G72M normally utilizes samples of approximately 0.20 +/-6 0.03-g mass, a starting pressure of 10.3 MPa 10.3 MPa
[1500 psi] and a temperature ramp rate of 5 °C ⁄min. However, Autogenous Ignition Temperatures (AIT) can also be obtained under other test conditions.
Testing experience has shown that AIT testing of volatile liquids can be influenced by the sample pre-conditioning and the sample mass. This will be
addressed in the standard as Special Case 1 in subsection 8.2.2. Testing experience has also shown that AIT testing of solid or non-volatile liquid materials
at low pressures (i.e., < 2.1 MPa) (that is, < 2.1 MPa) can be significantly influenced by the sample mass and the temperature ramp rate. This will be
addressed in the standard as Special Case 2, in subsection 8.2.3. Since the AIT of a material is dependent on the sample mass/configuration and test
conditions, any departure from the standard conditions normally used for Test Method G72/G72M testing should be clearly indicated in the test report.
1.3 This test method is for high-pressure pure oxygen. The test method may be used in atmospheres from 0.5 % to 100 % oxygen.
1.4 An apparatus suitable for these requirements is described. This test method could be applied to higher pressures and materials
of higher ignition temperature. If more severe requirements or other oxidizers than those described are desired, care must be taken
in selecting an alternative safe apparatus capable of withstanding the conditions.
1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
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 and healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
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 the jurisdiction of ASTM Committee G04 on Compatibility and Sensitivity of Materials in Oxygen Enriched Atmospheres and is the direct
responsibility of Subcommittee G04.01 on Test Methods.
Current edition approved Oct. 1, 2015Jan. 1, 2024. Published October 2015February 2024. Originally approved in 1982. Last previous edition approved in 20092015 as
G72/G72M – 09.G72/G72M – 15. DOI: 10.1520/G0072_G0072M-15.10.1520/G0072_G0072M-24.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G72/G72M − 24
2. Referenced Documents
2.1 ASTM Standards:
D1193 Specification for Reagent Water
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
G93 Guide for Cleanliness Levels and Cleaning Methods for Materials and Equipment Used in Oxygen-Enriched Environments
2.2 Federal Specification:
BB-O-925 Oxygen, Technical, Gas and Liquid
2.3 Other Documents:
MNL 36 Safe Use of Oxygen and Oxygen Systems: Guidelines for Oxygen System Design, Materials, Selection, Operations,
Storage, and Transportation
Compressed Gas Association Booklets G-1 and G-4.1
3. Summary of Test Method
3.1 This autogenous ignition temperature test method is designed to expose solid or liquid sample material to increasing
temperature in a high-pressure reaction vessel. The reaction vessel (bomb), including a sample holding assembly, is pressurized
with the oxygen-enriched environment. The bomb is heated in an electric furnace at a predetermined rate. The temperature of the
sample-holding assembly is monitored as a function of time by means of a thermocouple and recording potentiometer.
3.2 The minimum temperature required to cause the sample to ignite spontaneously is determined at any selected system pressure.
The point at which spontaneous ignition occurs is denoted by a sudden rise in temperature and the destruction of the sample. The
amount of rise in temperature is related to the sample size. A sample size is selected to prevent damage to the equipment caused
by exceeding safe system pressure or temperature limits because of the temperature rise.
3.3 The system is pressurized to the desired test pressure at the start of the test. During the test as the temperature is increased,
the pressure increases. No effort is made to control the pressure during the test. It is monitored only so that the pressure does not
exceed a safe limit for the test equipment.
FIG. 1 AIT Equipment Assembly
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
www.access.gpo.gov.
ASTM Manual Series, Available from ASTM International, 100 Barr Harbor Drive, W. Conshohocken, PA 19428.
Available from Compressed Gas Association (CGA), 4221 Walney Rd., 5th Floor, Chantilly, VA 20151-2923, http://www.cganet.com.
G72/G72M − 24
4. Significance and Use
4.1 Most organic liquids and solids will ignite in a pressurized oxidizing gas atmosphere if heated to a sufficiently high
temperature and pressure. This procedure provides a numerical value for the temperature at the onset of ignition under carefully
controlled conditions. Means for extrapolation from this idealized situation to the description, appraisal, or regulation of fire and
explosion hazards in specific field situations, are not established. Ranking of the ignition temperatures of several materials in the
standard apparatus is generally in conformity with field experience.
4.2 The temperature at which material will ignite spontaneously (AIT) will vary greatly with the geometry of the test system and
the rate of heating. To achieve good interlaboratory agreement of ignition temperatures, it is necessary to use equipment of
approximately the dimensions described in the test method. It is also necessary to follow the described procedure as closely as
possible.
4.3 The decomposition and oxidation of some fully fluorinated materials releases so little energy that there is no clear-cut
indication of ignition. Nor will there be a clear indication of ignition if a sample volatilizes, distilling to another part of the reaction
vessel, before reaching ignition temperature.
5. Apparatus
5.1 Suitable components shall be assembled so that the specified reaction vessel (bomb), including sample-holding assembly, can
be charged with oxygen and heated. The assembly shall provide a means of recording time and temperature at which ignition
occurs. A suitable assembly is illustrated in Fig. 1.
5.2 Cylinder Oxygen, conforming to Federal Specification BB-O-925, Type I or oxygen of 99.5 % minimum purity. Oxygen of
higher purity may be used if desired.
5.3 Line Filter, sintered stainless steel, tin-bronze, 5-μm porosity, maximum pressure 206.8 MPa [30 000 206.8 MPa [30 000 psi],
1 1
for 6.35-mm [ ⁄4-in.] high-pressure tubing with a 3.18-mm [ ⁄8-in.] port.
5.4 Compressor Pumps, diaphragm-type, air-driven.air-driven, 10 000 psi output pressure.
5.5 Valves, 6.35 mm 6.35 mm [ ⁄4 in.], in.] high-pressure, 206.8 MPa [30 000 psi] working pressure, nonrotating stem valves.
5.6 Pressure Gage, 20.7 MPa [3000 psi], 216 mm [8 ⁄2 in.].in.], Heise 2 or equivalent has been found satisfactory.0.1 % F.S.
Accuracy.
5.7 Connecting Tubing, Type 316 stainless steel, 6.35 mm [ ⁄4 in.], in.] high-pressure tubing, 448.1 MPa [65 000 psi] [65 000 psi]
pressure rating at 37.8 °C [100 °F].
5.8 High-Pressure Tees, Type 316 stainless steel with gland nuts and sleeves of Type 416 stainless steel, 6.35 mm [ ⁄4 in.]
high-pressure. Superpressure, Inc., Catalog No. 45-14311.All connection fittings shall be of cold-drawn Type 316 stainless steel,
1 9
413.7 MPa [60 000 psi] maximum pressure, tubing size 6.35 mm [ ⁄4 in.] high-pressure and 14.3-mm [ ⁄16-in.] insertion depth.
5.9 Pressure-Relief Blowout with Rupture Discs, pressure-relief blow-out assembly, Type 316 stainless steel, 6.35 mm [ ⁄4 in.], in.]
high-pressure, angle type with 48.3 MPa [7000 psi] at 22.2 °C [72 °F] rupture disks.
5.10 Reaction Vessel (Bomb)—A suitable reaction vessel for the test method is cylindrical, approximately 65 mm [2 ⁄16 in.] in
3 1
outside diameter and 298 mm [11 ⁄4 in.] long and weighs 9.75 kg [21 ⁄2 lb]. The vessel is bored from a solid forging of AISI 316SS
[8 ⁄4 in.] depth, with a volume equal to approximately 110 mL. The maximum working pressure at 427 °C [800 °F] is 82.7 MPa
[12 000 psi].
Catalog No. 49-14405 available from Superpressure, Inc., Silver Spring, Md. 20910 or equivalent has been found satisfactory.
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FIG. 2 Sample Holding Assembly
5.11 Thermocouple Assembly—A Chromel-Alumel thermocouple with suitable high-pressure fittings for the reaction vessel with
a 203-mm [8-in.] thermocouple to extend into the reaction chamber.
5.12 Heating Jacket—A 230-V, 1000-W single-phase heating jacket designed to fit the reaction vessel should be used.
5.13 Recorder, 00 °C to 1000 °C [0[0 °F to 2000 °F]—A strip chart recording pyrometer in the temperature range for the test
method should be used. The scale must be such that a sudden change of 20 °C [36 °F] or more in temperature in the reaction vessel
is clearly indicated.
5.14 Inner Reaction Vessel—A borosilicate glass test tube 15 by 125 mm.15 mm by 125 mm.
5.15 Sample Holder—A borosilicate glass culture tube 10 by 75 mm.
5.16 Wire Support, fashioned from Chromel A, 20 % Chromuim, 80 % Nickel, No. 21 AWG wire. Several turns of wire are wound
on a mandrel of sufficient size so that the resulting spring-like structure fits the inner reaction vessel snugly. A loop of wire is bent
to hold the vessel at the proper height, positioning the thermocouple assembly in the mouth of the sample holder (Fig. 2).
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FIG. 3 Inner Reaction Vessel Stopper
5.17 Support Bushing, fitting into the reaction vessel cover and supporting the entire sample-holding assembly.
5.18 Inner Reaction Vessel Stopper, fashioned from 12.5-mm borosilicate glass tubing to fit in the inner reaction vessel. It must
also conform to the dimensions in Fig. 3.
6. Materials
6.1 Nitric Acid—Consisting of 5 % by volume of Analytical Reagent grade nitric acid and deionized water.
6.2 Alkaline Cleaner—Consisting of a solution of 15 g of sodium hydroxide (NaOH), 15 g of trisodium phosphate (Na PO ), and
3 4
1 L of distilled or deionized water.
6.3 Deionized or Distilled Water, conforming to Specification D1193, Type IV.
6.4 Oxygen, conforming to Federal Specification BB-0-925, Type I or oxygen of 99.5 % purity. Oxygen of higher purity may be
used if desired.
7. Safety Precautions
7.1 Nitric Acid:
Warning! Harmful by inhalation, skin contact, and if swallowed.
Although not combustible, is a powerful oxidizing agent, which may cause combustible materials to ignite.
Wear appropriate NIOSH-approved respirator, chemical resistant gloves (Butyl(butyl rubber), safety goggles.
7.2 Sodium Hydroxide:
Warning! Harmful by inhalation, skin contact, and if swallowed.
Catalog No. 15-21AF1HM4-T available from High Pressure Equipment Co., 1222 Linden Ave., Erie, PA. 16505 or equivalent has been found satisfactory.
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Use adequate ventilation.
Wear face shield, lab coat, rubber apron.
Store away from strong acids
7.3 Oxygen:
Warning! Oxygen vigorously accelerates combustion.
Keep oil and grease away. Do not use oil or grease on regulators, gages, or control equipment.
Use only with equipment conditioned for oxygen service by carefully cleaning to remove oil, grease, and other combustibles.
Keep combustibles away from oxygen and eliminate ignition sources.
Keep surfaces clean to prevent ignition or explosion, or both, on contact with oxygen.
Always use a pressure regulator. Release regulator tension before opening cylinder valve.
All equipment and containers used must be suitable and recommended for oxygen service.
Never attempt to transfer oxygen from cylinder in which it is received to any other cylinder. Do not mix gases in cylinders.
Do not drop cylinder. Make
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