ASTM D2863-23

Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index)

SIGNIFICANCE AND USE
5.1 This test method provides for the measuring of the minimum concentration of oxygen in a flowing mixture of oxygen and nitrogen that will just support flaming combustion of plastics. Correlation with burning characteristics under actual use conditions is not implied.  
5.2 In this test method, the specimens are subjected to one or more specific sets of laboratory test conditions. If different test conditions are substituted or the end-use conditions are changed, it is not always possible by or from this test to predict changes in the fire-test-response characteristics measured. Therefore, the results are valid only for the fire-test-exposure conditions described in this test method.
SCOPE
1.1 This fire-test-response standard describes a procedure for measuring the minimum concentration of oxygen, expressed as percent volume, that will just support flaming combustion in a flowing mixture of oxygen and nitrogen.  
1.2 This test method provides three testing procedures. Procedure A involves top surface ignition, Procedure B involves propagating ignition, and Procedure C is a short procedure involving the comparison with a specified minimum value of the oxygen index.  
1.3 Test specimens used for this test method are prepared into one of six types of specimens (see Table 1).    
1.4 This test method provides for testing materials that are structurally self-supporting in the form of vertical bars or sheet up to 10.5-mm thick. Such materials are solid, laminated or cellular materials characterized by an apparent density greater than 15 kg/m3.  
1.5 This test method also provides for testing flexible sheet or film materials, while supported vertically.  
1.6 This test method is also suitable, in some cases, for cellular materials having an apparent density of less than 15 kg/m3.
Note 1: Although this test method has been found applicable for testing some other materials, the precision of the test method has not been determined for these materials, or for specimen geometries and test conditions outside those recommended herein.  
1.7 This test method measures and describes the response of materials, products, or assemblies to heat and flame under controlled conditions, but does not by itself incorporate all factors required for fire hazard or fire risk assessment of the materials, products, or assemblies under actual fire conditions.  
1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.9 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 hazards statement are given in Section 10.  
1.10 Fire testing is inherently hazardous. Adequate safeguards for personnel and property shall be employed in conducting these tests.
Note 2: This test method and ISO 4589-2 are technically equivalent when using the gas measurement and control device described in 6.3.1, with direct oxygen concentration measurement.  
1.11 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.

General Information

• Status: Published
• Publication Date: 30-Sep-2023
• ICS: 83.080.01 - Plastics in general
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.30 - Thermal Properties

Relations

• Replaces: ASTM D2863-19 - Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index)
• Effective Date: 01-Oct-2023
• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM E176-24 - Standard Terminology of Fire Standards
• Effective Date: 01-Jan-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM D883-22 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2022
• Refers: ASTM E456-13a(2022) - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E176-21ae1 - Standard Terminology of Fire Standards
• Effective Date: 01-Dec-2021
• Referred By: ASTM G94-22 - Standard Guide for Evaluating Metals for Oxygen Service
• Effective Date: 01-Oct-2023
• Referred By: ASTM F1870-22 - Standard Guide for Selection of Fire Test Methods for the Assessment of Upholstered Furnishings in Detention and Correctional Facilities
• Effective Date: 01-Oct-2023
• Referred By: ASTM G127-15(2023) - Standard Guide for the Selection of Cleaning Agents for Oxygen-Enriched Systems
• Effective Date: 01-Oct-2023
• Referred By: ASTM G114-21 - Standard Practices for Evaluating the Age Resistance of Polymeric Materials Used in Oxygen Service
• Effective Date: 01-Oct-2023
• Referred By: ASTM D6817/D6817M-17(2021) - Standard Specification for Rigid Cellular Polystyrene Geofoam
• Effective Date: 01-Oct-2023
• Referred By: ASTM D8501-23 - Standard Classification System for and Basis for Specification for Unfilled Poly(Ether Ketone Ketone) (PEKK) Materials for Molding, Extrusion, Composites, Powder Coating and Additive Manufacturing
• Effective Date: 01-Oct-2023
• Referred By: ASTM D3013-13(2021) - Standard Specification for Epoxy Molding Compounds
• Effective Date: 01-Oct-2023

Overview

ASTM D2863-23, titled Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index), is a widely recognized standard published by ASTM International. This method establishes a laboratory procedure for determining the minimum oxygen concentration-known as the oxygen index-that just supports flaming combustion of plastic materials in a controlled oxygen/nitrogen atmosphere. This procedure is primarily used for solid, laminated, or cellular plastics, as well as flexible films and sheets, to evaluate their tendency to sustain combustive reactions.

The primary objective of ASTM D2863-23 is to provide a repeatable and reliable measure of the flammability of plastics under controlled test conditions. While not intended to replicate real-world fire scenarios or serve as a definitive fire hazard assessment, the oxygen index value is a critical property for quality control, product development, and regulatory compliance in industries utilizing plastic materials.

Key Topics

• Oxygen Index Measurement
  The core of the method is the determination of the minimum percentage of oxygen necessary in a flowing oxygen-nitrogen mixture to just sustain a candle-like combustion of plastics.

• Test Procedures
  The standard defines three procedures:

  • Procedure A: Top surface ignition of the specimen.
  • Procedure B: Propagating ignition down the sides of the specimen.
  • Procedure C: Short protocol for comparison with a specified minimum oxygen index value.

• Specimen Types and Preparation
  Suitable for:

  • Structurally self-supporting materials (solid, laminated, or cellular with density >15 kg/m³ and up to 10.5 mm thick)
  • Flexible sheets or films, which are tested while supported vertically
  • Select cellular materials with densities <15 kg/m³ Six different specimen forms accommodate the wide range of plastics in the market.

• Controlled Laboratory Testing
  Testing is performed in a transparent chimney with precise gas flow rates and temperature control. Oxygen concentration is adjusted until the material can just sustain flaming combustion. The response is meticulously observed and criteria are applied to determine the oxygen index.

• Limitations

  • The results are valid only for the specific laboratory conditions described in the standard.
  • Not all fire hazard factors present in real use conditions are considered in this test.
  • Safety outcomes may differ under actual fire exposure.

Applications

• Material Selection and Product Development
  Oxygen index testing is used by engineers and product designers to compare the flammability of different plastic materials, guiding choices for safer products.

• Regulatory Compliance and Quality Assurance
  Many industries, including construction, transportation, and electronics, use this standard as part of their fire safety and quality control programs to ensure materials meet prescribed oxygen index thresholds.

• Comparative Testing
  The standard enables manufacturers to benchmark materials against industry norms, client requirements, or regulatory specifications.

• Research and Development
  R&D laboratories use oxygen index values to quantify improvements in flame resistance brought by additives or changes in polymer formulation.

Related Standards

• ISO 4589-2 - Plastics-Determination of Flammability by Oxygen Index-Part 2: Ambient Temperatures (ASTM D2863-23 is technically equivalent when specific apparatus is used)
• ASTM D618 - Practice for Conditioning Plastics for Testing
• ASTM D883 - Terminology Relating to Plastics
• ASTM D1622 - Test Method for Apparent Density of Rigid Cellular Plastics
• ASTM E176 - Terminology of Fire Standards

Practical Value

ASTM D2863-23 is crucial for anyone needing reliable, standardized data on the flammability of plastics. By measuring the minimum oxygen concentration required to support combustion, this method offers a consistent benchmark for fire safety in plastics. It supports product innovation, regulatory approval, and continuous improvement in the use of plastics across various industries, all while promoting improved fire safety and quality assurance practices.

Keywords: ASTM D2863-23, oxygen index, plastics flammability, minimum oxygen concentration, candle-like combustion, standardized test method, fire safety, quality control, laboratory testing, regulatory compliance.

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: D2863 − 23
Standard Test Method for
Measuring the Minimum Oxygen Concentration to Support
Candle-Like Combustion of Plastics (Oxygen Index)
This standard is issued under the fixed designation D2863; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 1.9 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This fire-test-response standard describes a procedure
responsibility of the user of this standard to establish appro-
for measuring the minimum concentration of oxygen, ex-
priate safety, health, and environmental practices and deter-
pressed as percent volume, that will just support flaming
mine the applicability of regulatory limitations prior to use.
combustion in a flowing mixture of oxygen and nitrogen.
Specific hazards statement are given in Section 10.
1.2 This test method provides three testing procedures.
1.10 Fire testing is inherently hazardous. Adequate safe-
Procedure A involves top surface ignition, Procedure B in-
guards for personnel and property shall be employed in
volves propagating ignition, and Procedure C is a short
conducting these tests.
procedure involving the comparison with a specified minimum
NOTE 2—This test method and ISO 4589-2 are technically equivalent
value of the oxygen index.
when using the gas measurement and control device described in 6.3.1,
with direct oxygen concentration measurement.
1.3 Test specimens used for this test method are prepared
1.11 This international standard was developed in accor-
into one of six types of specimens (see Table 1).
dance with internationally recognized principles on standard-
1.4 This test method provides for testing materials that are
ization established in the Decision on Principles for the
structurally self-supporting in the form of vertical bars or sheet
Development of International Standards, Guides and Recom-
up to 10.5-mm thick. Such materials are solid, laminated or
mendations issued by the World Trade Organization Technical
cellular materials characterized by an apparent density greater
Barriers to Trade (TBT) Committee.
than 15 kg/m .
2. Referenced Documents
1.5 This test method also provides for testing flexible sheet
or film materials, while supported vertically.
2.1 ASTM Standards:
D618 Practice for Conditioning Plastics for Testing
1.6 This test method is also suitable, in some cases, for
D883 Terminology Relating to Plastics
cellular materials having an apparent density of less than 15
D1071 Test Methods for Volumetric Measurement of Gas-
kg/m .
eous Fuel Samples
NOTE 1—Although this test method has been found applicable for
testing some other materials, the precision of the test method has not been D1622 Test Method for Apparent Density of Rigid Cellular
determined for these materials, or for specimen geometries and test
Plastics
conditions outside those recommended herein.
D4802 Specification for Poly(Methyl Methacrylate) Acrylic
1.7 This test method measures and describes the response of
Plastic Sheet
materials, products, or assemblies to heat and flame under
D4968 Practice for Annual Review of Test Methods and
controlled conditions, but does not by itself incorporate all
Specifications for Plastics
factors required for fire hazard or fire risk assessment of the
E176 Terminology of Fire Standards
materials, products, or assemblies under actual fire conditions.
E177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
1.8 The values stated in SI units are to be regarded as
E456 Terminology Relating to Quality and Statistics
standard. No other units of measurement are included in this
E691 Practice for Conducting an Interlaboratory Study to
standard.
Determine the Precision of a Test Method
This test method is under the jurisdiction of ASTM Committee D20 on Plastics
and is the direct responsibility of Subcommittee D20.30 on Thermal Properties. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2023. Published October 2023. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1970. Last previous edition approved in 2019 as D2863 - 19. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D2863-23. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2863 − 23
TABLE 1 Test Specimen Dimensions
transparent chimney. The upper end of the specimen is ignited
Dimensions and the subsequent burning behavior of the specimen is
Test
Specimen Material Form
Length, Width, Thickness, observed to compare the period for which burning continues,
A
Type
mm mm mm
or the length of specimen burnt, with specified limits for each
I 80 to 150 10 ± 0.5 4 ± 0.25 for molding materials
burning. By testing a series of specimens in different oxygen
II 80 to 150 10 ± 0.5 10 ± 0.5 for cellular materials
B concentrations, the minimum oxygen concentration is deter-
III 80 to 150 10 ± 0.5 # 10.5 for sheet materials
IV 70 to 150 6.5 ± 0.5 3 ± 0.25 alternative size for mined.
self-supporting molding
4.2 Three procedures are included in this test method. In
or sheet materials
B
V 140 ± 5 52 ± 0.5 #10.5 for flexible film or sheet
Procedure A, a complete assessment of the oxygen index is
B, C
VI 140 to 200 20 0.02 to for thin film; limited to film
conducted using top surface ignition. In Procedure B, a
0.10 that can be rolled by the
complete assessment of the oxygen index is conducted using
wire specified in 6.7
A
propagating ignition. Procedure C provides a comparison with
Test specimens of Types I, II, III, and IV are suitable for materials that are
self-supporting at these dimensions. Test specimens of Form V and VI are suitable
a specified minimum value of oxygen index and can be
for materials that require support during testing. Test specimens of Form VI are
conducted using top surface ignition or propagating ignition.
suitable for film materials that can be rolled into a self-supporting specimen by the
procedure in 7.4.
5. Significance and Use
B
Compare results obtained using Type III, V, and VI test specimens only to those
obtained using specimens of the same form and thickness. It is assumed that the
5.1 This test method provides for the measuring of the
amount of variation in thickness for such materials will be controlled by other
minimum concentration of oxygen in a flowing mixture of
standards.
C
The test specimen of Type VI is suitable for thin film that is self-supporting when
oxygen and nitrogen that will just support flaming combustion
it is rolled (see 7.4). Dimensions in the table are of the specimen size from which
of plastics. Correlation with burning characteristics under
the rolled form is made. If the film is very thin, it is possible that proper results will
actual use conditions is not implied.
only be obtained if two or more layers are combined in the preparation of the roll
to obtain proper results.
5.2 In this test method, the specimens are subjected to one
or more specific sets of laboratory test conditions. If different
test conditions are substituted or the end-use conditions are
E2935 Practice for Evaluating Equivalence of Two Testing
changed, it is not always possible by or from this test to predict
Processes
changes in the fire-test-response characteristics measured.
2.2 ISO Standards:
Therefore, the results are valid only for the fire-test-exposure
ISO 4589-2 Plastics—Determination of Flammability by
conditions described in this test method.
Oxygen Index—Part 2, Ambient Temperatures
ISO 7823-1 Poly(Methylmethacrylate) Sheets—Types, Di- 6. Apparatus
mensions and Characteristics—Part 1—Cast Sheets
6.1 Test Chimney. The test chimney consists of a heat-
ISO 13943 Fire Safety—Vocabulary
resistant glass tube of 75 to 100-mm inside diameter and 450
to 500-mm height. The opening at the top of the chimney shall
3. Terminology
be restricted to provide an outlet of 40 6 2-mm diameter, either
3.1 Definitions—For definitions of terms relating to plastics,
by providing an overhead cap or by designing the glass
the definitions in this test method are in accordance with
chimney appropriately. The bottom of the chimney, or the base
Terminology D883. For terms relating to fire, the definitions in
to which the tube is attached, shall contain noncombustible
this test method are in accordance with Terminology E176 and
material to evenly mix and distribute the gas mixture entering
ISO 13943. In case of conflict, the definitions given in
at this base. Glass beads 3 to 5 mm in diameter in a bed 80 to
Terminology E176 shall prevail. For terms relating to precision
100-mm deep have been found suitable. The chimney shall be
and bias and associated issues, the terms used in this test
mounted securely on the base to prevent air leaks. One
method are in accordance with the definitions in Terminology
example of a design is shown in Fig. 1.
E456.
NOTE 3—It is helpful to place a wire screen above the noncombustible
3.2 Definitions of Terms Specific to This Standard:
material to catch falling fragments and to aid in keeping the base of the
3.2.1 ignition—the initiation of combustion. column clean.
3.2.2 oxygen index (OI)—the minimum concentration of 6.2 Specimen Holders
oxygen, expressed as volume percent, in a mixture of oxygen 6.2.1 Specimen Holder for Self-Supporting Specimens—
and nitrogen that will just support flaming combustion of a Any small holding device that will support the specimen at its
material initially at 23 6 2°C under the conditions of this test base and hold it vertically in the center of the chimney is an
method. acceptable specimen holder. A typical arrangement (see Fig. 1)
consists of a laboratory thermometer clamp inserted into the
4. Summary of Test Method
end of a glass tube held in place by glass beads or otherwise
4.1 A small test specimen is supported vertically in a firmly supported.
6.2.2 Specimen Holder for Specimens of Flexible Sheet or
mixture of oxygen and nitrogen flowing upwards through a
Film Materials that Require Support—A specimen holder for
flexible film or sheet materials that require support shall be able
Available from International Organization for Standardization (ISO), ISO
to support the specimen by both vertical edges in a frame
Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
Geneva, Switzerland, http://www.iso.org. equivalent to that illustrated by Fig. 2, with reference marks at
D2863 − 23
1. Burning Specimen 6. Glass Beads in a Bed 11. Pressure Gauge
2. Clamp with Rod Support 7. Brass Base 12. Precision Pressure Regulator
3. Igniter 8. Tee 13. Filter
4. Wire Screen 9. Cut-Off Valve 14. Needle Valve
5. Ring Stand 10. Orifice in Holder 15. Rotameter
FIG. 1 Typical Equipment Layout
20 and 100 mm below the top of the frame. The profile of the mixture with a precision of 60.1 %, by volume, of the gas
holder and its support shall be smooth to minimize induction of mixture, when the gas velocity through the chimney is 40 6 2
turbulence in the rising flow of gas. mm/s at 23 6 2°C.
6.2.3 Thin Film Rolling Tool—In order to prepare self-
6.3.1 The system for direct gas measurement and control
supporting specimens from thin films (see 7.4), use a 2 6
involves needle valves on individual and mixed gas supply
0.1-mm stainless steel rod with a 0.3 6 0.05-mm slit at one
lines, a paramagnetic oxygen analyzer that continuously
end, equivalent to that illustrated in Fig. 3. The actual specimen
samples the mixed gas, and a flow meter to indicate when the
holder shall be the one in 6.2.1.
gas flow through the chimney is within the required limits.
6.3 Gas Measurement and Control Devices. Gas measure- 6.3.2 An alternate system for gas measurement is described
ment and control devices shall be suitable for measuring the in Annex A4. The system used for indirect gas measurement
concentration of oxygen in the gas mixture entering the (Annex A4) requires calibration after assembly to ensure that
chimney with an accuracy of 60.5 %, by volume, of the gas the compounded errors of the component parts do not exceed
mixture and for adjusting the concentration of oxygen in the the requirements of 6.3.
D2863 − 23
FIG. 2 Frame Design
6 2°C. If this involves an internal probe, its position and
profile shall be designed to minimize induction of turbulence
within the chimney.
6.4 Flame Igniter. The flame igniter shall comprise a tube,
with an inside diameter of 2 6 1 mm, that can be inserted into
the chimney to apply the test flame.
6.4.1 The fuel supply shall be adjusted so that the flame
height is 16 6 4 mm (measured from the bottom of the flame
to the top of the flame) when the flame igniter tube is vertical
within the chimney and the flame is burning within the
chimney atmosphere (see Fig. 4).
6.4.2 The flame fuel shall be one of the following: methane,
or natural gas of at least 97 % purity, or propane of at least
98 % purity. The flame fuel shall have no premixed air.
6.5 Timing Device. A timing device shall be provided,
which is capable of measuring periods up to 5 min with an
accuracy of 60.5 s.
6.6 Fume Extraction System. A fume extraction system shall
be provided with sufficient ventilation or exhaust to remove
fumes or soot expelled from the chimney without disrupting
FIG. 3 Rod with a Slit
the gas-flow rate or temperatures in the chimney.
NOTE 4—If soot-generating materials are being tested, it is likely that
6.3.3 Means shall be provided for checking or ensuring that
the glass chimney, gas inlets, and inlet screen will require cleaning
the temperature of the gas mixture entering the chimney is 23 between tests to maintain good visibility and to function properly.
D2863 − 23
FIG. 4 Oxygen Index Apparatus Schematic Showing Igniter Flame Detail
6.7 Gas Supplies. The gas supplied to the test apparatus 7.1.3 Record the position and orientation of the test speci-
shall consist of pressurized sources of oxygen or nitrogen, or mens with respect to any asymmetry in the sample material
both, not less than 98 % pure or clean dry air, or both, (see Note 6).
(containing 20.9 % oxygen), as appropriate.
NOTE 6—Oxygen index results are likely to be significantly affected by
6.7.1 The gas mixture entering the chimney shall have a
differences in burning behavior, due to material inhomogeneity (for
moisture content of <0.1 %, unless the results have been shown
example, different levels of shrinkage when heated for specimens cut in
to be insensitive to higher moisture levels in the gas mixture. different directions from asymmetrically-oriented thermoplastics film).
The gas supply system shall incorporate a drying device, or
7.1.4 The test specimens shall conform to the dimensions
provision for monitoring or sampling the gas supply for
and geometry listed in Table 1. If non-standard size specimens
moisture content, unless the moisture content of the gas
are used, a difference in oxygen index is likely to result.
supplies is known to be acceptable.
7.1.5 It is likely that, for materials where the oxygen index
NOTE 5—It must be noted that bottled oxygen or nitrogen will not
is known to within 62 % by volume, 15 test specimens will be
always contain <0.1 % of water; moisture contents of 0.003 to 0.01 % are
sufficient. However, for materials of unknown oxygen index, or
typical for commercial supplies as filled bottles >98 % pure, but as such
which exhibit erratic burning characteristics, between 15 and
bottled gases are depressured to below about 1 MPa, the moisture content
30 test specimens are likely to be required.
of the gas drawn off has been found to rise above 0.1 %.
7.2 Self-Supporting Specimens (Specimen Types I, II, III,
7. Test Specimens
and IV)
7.1 General: 7.2.1 The specimens shall be prepared in accordance with
7.1.1 The specimens shall be die-punched, cut by hand 7.1.
using a razor blade or other sharp tool, or cut by an automatic
7.3 Specimens of Flexible Sheet or Film Materials that
machine. Alternatively, specimens shall be prepared directly by
Require Support (Specimen Type IV)
injection molding.
7.3.1 The specimens shall be prepared in accordance with
7.1.2 Ensure that the surfaces of the specimens are clean and
7.1 and they shall be supported by both vertical edges in a
free from flaws that could affect burning behavior, for example,
frame equivalent to that illustrated by Fig. 2 (see 6.2.2).
peripheral molding flash or burrs from machining. The edges
of the specimens shall be smooth and free from fuzz or burrs 7.4 Self-Supporting Specimens Rolled from Thin Films
of material left from machining or molding. (Specimen Type VI)
D2863 − 23
7.4.1 For preparation of Type VI specimens, use the rolling 8. Conditioning
tool described in 6.2.3.
8.1 Unless otherwise specified, each test specimen shall be
7.4.2 Specimen films shall be prepared in accordance with
conditioned for at least 40 h at 23 6 2°C and 50 6 5 % relative
7.1.
humidity (RH) immediately prior to use in accordance with
7.4.3 Insert one corner of the film into the slit of the thin Practice D618.
film rolling tool and then wind the film around the rod in a
8.2 Maintain the ambient conditions for the test apparatus at
spiral of 45°, as shown in Fig. 3. Ensure that the 45° angle is
23 6 5°C. Keep the test specimens in an enclosure at 23 6 2°C
maintained during the winding process so that the film reaches
and 50 6 5 % RH and take the test specimens out of the
exactly to the end of the tool, to produce a test piece of the
enclosure just before testing (so that testing is conducted within
correct length. After the winding is finished, tape the last end
30 minutes of the test specimen removal from the conditioning
of the roll while the material is still on the stainless steel rod to
environment).
prevent loosening. Then pull the rod out of the rolled film.
7.4.4 Cut off the rolled film at a distance of 20 mm from the 9. Calibration of Apparatus
top end. See Fig. 5.
9.1 Calibration for systems with direct oxygen gas concen-
7.5 Specimen Marking tration measurement. Calibrate the system for direct oxygen
gas concentration measurement with a paramagnetic oxygen
7.5.1 For monitoring the distance over which burning
analyzer, used for the measurements in 6.3.1, by the following:
occurs, mark the specimen with transverse lines at one or more
(a) turning the nitrogen flow on and closing the oxygen flow
levels which are dependent upon the specimen form and the
and confirming that the oxygen concentration on the display
ignition procedure to be used. Structurally self-supporting
reads 0.0 %, and (b) turning the oxygen flow on and closing the
specimens shall be marked on at least two adjacent faces. If
nitrogen flow and confirming that the oxygen concentration on
wet inks are used, ensure that the marks are dry before the
the display reads the same value as the concentration of oxygen
specimen is ignited.
in the supply gas (see 6.7).
7.5.2 If test specimens of Type I, II, III, IV, or VI are to be
9.2 Calibration for systems using indirect gas measurement
tested in accordance with Procedure A, they shall be marked 50
in accordance with Annex A4. Calibrate the flow-measuring
mm from the end to be ignited. If specimens of Type I, II, III,
system used for the indirect measurements of oxygen concen-
IV, and VI are to be tested in accordance with Procedure B,
tration and flow rate with the instrumentation in 6.3.2 using a
they shall be marked at 10 mm and at 60 mm from the end to
water-sealed rotating drum meter (wet test meter) in accor-
be ignited.
dance with Test Method D1071 or by equivalent calibration
7.5.3 The reference marks for testing specimens of Type V
devices. The maximum interval between recalibration shall be
are carried by the supporting frame (see Fig. 2), but thermally
six months.
stable materials shall additionally be marked at 20 mm and at
9.3 A cast PMMA specimen shall be used as a verification
100 mm from the end to be ignited, for convenience.
material at least once a month. See Annex A1 for calibration
7.6 For cellular materials, the density shall be determined in
method.
accordance with Test Method D1622.
NOTE 7—It is possible that the oxygen index samples of cellular
10. Hazards
materials that contain volatile flammable blowing agents that diffuse from
the sample will change with time. 10.1 The exhaust system must be so designed and operated
that the laboratory environment is protected from smoke and
gases or vapors. The operator shall be instructed on ways to
minimize exposure to combustion products by following sound
safety and industrial hygiene practices. For example, ensure
that the exhaust system is working properly and wear appro-
priate clothing including gloves, safety glasses, breathing
apparatus (when hazardous fumes are expected).
10.2 During this test, high temperatures are generated that
are capable of igniting some clothing following even brief
exposures. Precautions shall be taken to avoid ignitions of this
type.
11. Symbols and Criteria for This Test Method
11.1 Test Method Criteria:
11.1.1 The criteria for oxygen index measurements are
described in Table 2.
11.1.2 The extent of burning in this test method is consid-
FIG. 5 Rolled Film ered to have been exceeded when any part of the visibly
D2863 − 23
A
TABLE 2 Criteria for Oxygen Index Measurements
11.2.8 σ*—standard deviation of the oxygen concentration.
Alternative Criteria
11.2.9 d—interval between oxygen concentration levels in
Period of
Test Specimen
percent volume.
Ignition Procedure Burning
B
Type (See Table 1) Extent of Burning
After
11.2.10 k—a factor to be determined from Table 3.
Ignition(s)
11.2.11 n—number of measurements of oxygen concentra-
I, II, III, IV, and VI A 180 50 mm below the top
(top surface ignition) of the specimen
tion.
I, II, III, IV, and VI B 180 50 mm below the
(propagating ignition) upper reference
12. Test Procedure
mark
V propagating ignition 180 80 mm below the
NOTE 8—Some materials exhibit a non-flaming type of combustion (for
upper reference
example, glowing combustion) instead of, or at a lower oxygen concen-
mark (on the frame)
tration than that required for, flaming combustion. When testing such
A
The criteria in this table do not necessarily produce equivalent oxygen index
materials, it is necessary to identify the type of combustion for which the
results for specimens of differing shape or tested using different ignition conditions
oxygen index is required or measured.
or procedures.
B
The extent of burning is exceeded when any part of the visibly burning portion of
12.1 Procedure A
a specimen, including burning drips descending the vertical faces, passes the level
12.1.1 Select an initial concentration of oxygen to be used.
indicated in the column.
Whenever possible, base the initial concentration on experi-
ence of results for similar materials. Alternatively, try to ignite
a test specimen in air, and note the burning behavior. If the
burning portion of a specimen, including burning drips de-
specimen burns rapidly, select an initial concentration of about
scending the vertical faces, passes the level indicated in the
18 % oxygen; if the test specimen burns gently or unsteadily,
column.
select an initial oxygen concentration of about 21 %; if the
11.1.3 The criteria in Table 2 do not necessarily produce
specimen does not continue to burn in air, select an initial
equivalent oxygen index results for specimens of differing
concentration of at least 25 %, depending upon the difficulty of
shape or tested using different ignition conditions or proce-
ignition or the period of burning before extinguishing in air.
dures.
12.1.2 Record the oxygen concentration used as the volume
11.2 Method Symbols:
percent measured by an oxygen paramagnetic analyzer (if
11.2.1 C —oxygen concentration in percent volume.
o
present) or as the volume percent calculated in accordance with
11.2.2 C —final value of oxygen concentration in percent
F
the equations given in Annex A2 (if the system described in
volume.
6.3.2 is used).
11.2.3 C —each of the oxygen concentration percentages
i
12.1.3 Ensure that the test chimney is vertical (see Fig. 1).
used during measurement of the last six responses in the N
T
Verify that the temperature at the lower end of the chimney is
series.
at least 23 6 2°C.
11.2.4 O—neither the period or extent of burning exceeds
the relevant limit specified in Table 2. 12.1.4 Mount a specimen vertically in the center of the
11.2.5 X—the period or extent of burning exceeds the chimney so that the top of the specimen is at least 100 mm
relevant limit specified in Table 2. below the open top of the chimney and the lowest exposed part
11.2.6 N —series of “X” or “O” results. of the specimen is at least 100 mm above the top of the gas
L
11.2.7 N —series of “X” or “O” results plus five distribution device at the base of the chimney (see Fig. 1 or Fig.
T
(N = N + 5). 2, as appropriate, for guidance).
T L
TABLE 3 Determination of k
1 2 3 4 5 6
Values of k for which the first N determinations are:
Responses for the Last Five L Responses for the Last Five
A
Measurements Measurements
(a) O OO OOO OOOO
XOOOO −0.55 −0.55 −0.55 −0.55 OXXXX
XOOOX −1.25 −1.25 −1.25 −1.25 OXXXO
XOOXO 0.37 0.38 0.38 0.38 OXXOX
XOOXX −0.17 −0.14 −0.14 −0.14 OXXOO
XOXOO 0.02 0.04 0.04 0.04 OXOXX
XOXOX −0.50 −0.46 −0.45 −0.45 OXOXO
XOXXO 1.17 1.24 1.25 1.25 OXOOX
XOXXX 0.61 0.73 0.76 0.76 OXOOO
XXOOO −0.30 −0.27 −0.26 −0.26 OOXXX
XXOOX −0.83 −0.76 −0.75 −0.75 OOXXO
XXOXO 0.83 0.94 0.95 0.95 OOXOX
XXOXX 0.30 0.46 0.50 0.50 OOXOO
XXXOO 0.50 0.65 0.68 0.68 OOOXX
XXXOX −0.04 0.19 0.24 0.25 OOOXO
XXXXO 1.60 1.92 2.00 2.01 OOOOX
XXXXX 0.89 1.33 1.47 1.50 OOOOO
A
Values of k for which the first N determinations are (b) X, XX, XXX, and XXXX are as given in Table 3 opposite the appropriate response in Column 6, but with the sign
L
of k reversed, that is: OI = C − kd (see 13.1).
F
D2863 − 23
12.1.5 Set the gas mixing and flow controls so that an 12.1.9.7 Allow the chimney to regain a temperature of 23 6
oxygen/nitrogen mixture at 23 6 2°C, containing the desired 2°C, or replace it with another so conditioned.
concentration of oxygen, is flowing through the chimney at a
12.1.9.8 Install the next specimen.
rate 40 6 2 mm/s. Let the gas flow purge the chimney for at
NOTE 9—For screening purposes, it is acceptable to invert sufficiently
least 30 s prior to ignition of each specimen, and maintain
...

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: D2863 − 19 D2863 − 23
Standard Test Method for
Measuring the Minimum Oxygen Concentration to Support
Candle-Like Combustion of Plastics (Oxygen Index)
This standard is issued under the fixed designation D2863; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This fire-test-response standard describes a procedure for measuring the minimum concentration of oxygen, expressed as
percent volume, that will just support flaming combustion in a flowing mixture of oxygen and nitrogen.
1.2 This test method provides three testing procedures. Procedure A involves top surface ignition, Procedure B involves
propagating ignition, and Procedure C is a short procedure involving the comparison with a specified minimum value of the oxygen
index.
1.3 Test specimens used for this test method are prepared into one of six types of specimens (see Table 1).
1.4 This test method provides for testing materials that are structurally self-supporting in the form of vertical bars or sheet up to
10.5-mm thick. Such materials are solid, laminated or cellular materials characterized by an apparent density greater than 15 kg/m .
1.5 This test method also provides for testing flexible sheet or film materials, while supported vertically.
1.6 This test method is also suitable, in some cases, for cellular materials having an apparent density of less than 15 kg/m .
NOTE 1—Although this test method has been found applicable for testing some other materials, the precision of the test method has not been determined
for these materials, or for specimen geometries and test conditions outside those recommended herein.
1.7 This test method measures and describes the response of materials, products, or assemblies to heat and flame under controlled
conditions, but does not by itself incorporate all factors required for fire hazard or fire risk assessment of the materials, products,
or assemblies under actual fire conditions.
1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.9 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 hazards statement are given in Section 10.
1.10 Fire testing is inherently hazardous. Adequate safeguards for personnel and property shall be employed in conducting these
tests.
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.30 on Thermal Properties.
Current edition approved Oct. 1, 2019Oct. 1, 2023. Published October 2019October 2023. Originally approved in 1970. Last previous edition approved in 20172019 as
D2863 - 17a.D2863 - 19. DOI: 10.1520/D2863-19.10.1520/D2863-23.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2863 − 23
TABLE 1 Test Specimen Dimensions
Dimensions
Test
Specimen Material Form
Length, Width, Thickness,
A
Type
mm mm mm
I 80 to 150 10 ± 0.5 4 ± 0.25 for molding materials
II 80 to 150 10 ± 0.5 10 ± 0.5 for cellular materials
B
III 80 to 150 10 ± 0.5 # 10.5 for sheet materials
IV 70 to 150 6.5 ± 0.5 3 ± 0.25 alternative size for
self-supporting molding
or sheet materials
B
V 140 ± 5 52 ± 0.5 #10.5 for flexible film or sheet
B, C
VI 140 to 200 20 0.02 to for thin film; limited to film
0.10 that can be rolled by the
wire specified in 6.7
A
Test specimens of Types I, II, III, and IV are suitable for materials that are
self-supporting at these dimensions. Test specimens of Form V and VI are suitable
for materials that require support during testing. Test specimens of Form VI are
suitable for film materials that can be rolled into a self-supporting specimen by the
procedure in 7.4.
B
Compare results obtained using Type III, V, and VI test specimens only to those
obtained using specimens of the same form and thickness. It is assumed that the
amount of variation in thickness for such materials will be controlled by other
standards.
C
The test specimen of Type VI is suitable for thin film that is self-supporting when
it is rolled (see 7.4). Dimensions in the table are of the specimen size from which
the rolled form is made. If the film is very thin, it is possible that proper results will
only be obtained if two or more layers are combined in the preparation of the roll
to obtain proper results.
NOTE 2—This test method and ISO 4589-2 are technically equivalent when using the gas measurement and control device described in 6.3.1, with direct
oxygen concentration measurement.
1.11 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.
2. Referenced Documents
2.1 ASTM Standards:
D618 Practice for Conditioning Plastics for Testing
D883 Terminology Relating to Plastics
D1071 Test Methods for Volumetric Measurement of Gaseous Fuel Samples
D1622 Test Method for Apparent Density of Rigid Cellular Plastics
D4802 Specification for Poly(Methyl Methacrylate) Acrylic Plastic Sheet
D4968 Practice for Annual Review of Test Methods and Specifications for Plastics
E176 Terminology of Fire Standards
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E2935 Practice for Evaluating Equivalence of Two Testing Processes
2.2 ISO Standards:
ISO 4589-2 Plastics—Determination of Flammability by Oxygen Index—Part 2, Ambient Temperatures
ISO 7823-1 Poly(Methylmethacrylate) Sheets—Types, Dimensions and Characteristics—Part 1—Cast Sheets
ISO 13943 Fire Safety—Vocabulary
3. Terminology
3.1 Definitions—For definitions of terms relating to plastics, the definitions in this test method are in accordance with Terminology
D883. For terms relating to fire, the definitions in this test method are in accordance with Terminology E176 and ISO 13943. In
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 International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, http://www.iso.org.
D2863 − 23
case of conflict, the definitions given in Terminology E176 shall prevail. For terms relating to precision and bias and associated
issues, the terms used in this test method are in accordance with the definitions in Terminology E456.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 ignition—the initiation of combustion.
3.2.2 oxygen index (OI)—the minimum concentration of oxygen, expressed as volume percent, in a mixture of oxygen and
nitrogen that will just support flaming combustion of a material initially at 23 6 2°C under the conditions of this test method.
4. Summary of Test Method
4.1 A small test specimen is supported vertically in a mixture of oxygen and nitrogen flowing upwards through a transparent
chimney. The upper end of the specimen is ignited and the subsequent burning behavior of the specimen is observed to compare
the period for which burning continues, or the length of specimen burnt, with specified limits for each burning. By testing a series
of specimens in different oxygen concentrations, the minimum oxygen concentration is determined.
4.2 Three procedures are included in this test method. In Procedure A, a complete assessment of the oxygen index is conducted
using top surface ignition. In Procedure B, a complete assessment of the oxygen index is conducted using propagating ignition.
Procedure C provides a comparison with a specified minimum value of oxygen index and can be conducted using top surface
ignition or propagating ignition.
5. Significance and Use
5.1 This test method provides for the measuring of the minimum concentration of oxygen in a flowing mixture of oxygen and
nitrogen that will just support flaming combustion of plastics. Correlation with burning characteristics under actual use conditions
is not implied.
5.2 In this test method, the specimens are subjected to one or more specific sets of laboratory test conditions. If different test
conditions are substituted or the end-use conditions are changed, it is not always possible by or from this test to predict changes
in the fire-test-response characteristics measured. Therefore, the results are valid only for the fire-test-exposure conditions
described in this test method.
6. Apparatus
6.1 Test Chimney. The test chimney consists of a heat-resistant glass tube of 75 to 100-mm inside diameter and 450 to 500-mm
height. The opening at the top of the chimney shall be restricted to provide an outlet of 40 6 2-mm diameter, either by providing
an overhead cap or by designing the glass chimney appropriately. The bottom of the chimney, or the base to which the tube is
attached, shall contain noncombustible material to evenly mix and distribute the gas mixture entering at this base. Glass beads 3
to 5 mm in diameter in a bed 80 to 100-mm deep have been found suitable. The chimney shall be mounted securely on the base
to prevent air leaks. One example of a design is shown in Fig. 1.
NOTE 3—It is helpful to place a wire screen above the noncombustible material to catch falling fragments and to aid in keeping the base of the column
clean.
6.2 Specimen Holders
6.2.1 Specimen Holder for Self-Supporting Specimens—Any small holding device that will support the specimen at its base and
hold it vertically in the center of the chimney is an acceptable specimen holder. A typical arrangement (see Fig. 1) consists of a
laboratory thermometer clamp inserted into the end of a glass tube held in place by glass beads or otherwise firmly supported.
6.2.2 Specimen Holder for Specimens of Flexible Sheet or Film Materials that Require Support—A specimen holder for flexible
film or sheet materials that require support shall be able to support the specimen by both vertical edges in a frame equivalent to
that illustrated by Fig. 2, with reference marks at 20 and 100 mm below the top of the frame. The profile of the holder and its
support shall be smooth to minimize induction of turbulence in the rising flow of gas.
D2863 − 23
1. Burning Specimen 6. Glass Beads in a Bed 11. Pressure Gauge
2. Clamp with Rod Support 7. Brass Base 12. Precision Pressure Regulator
3. Igniter 8. Tee 13. Filter
4. Wire Screen 9. Cut-Off Valve 14. Needle Valve
5. Ring Stand 10. Orifice in Holder 15. Rotameter
FIG. 1 Typical Equipment Layout
6.2.3 Thin Film Rolling Tool—In order to prepare self-supporting specimens from thin films (see 7.4), use a 2 6 0.1-mm stainless
steel rod with a 0.3 6 0.05-mm slit at one end, equivalent to that illustrated in Fig. 3. The actual specimen holder shall be the one
in 6.2.1.
6.3 Gas Measurement and Control Devices. Gas measurement and control devices shall be suitable for measuring the
concentration of oxygen in the gas mixture entering the chimney with an accuracy of 60.5 %, by volume, of the gas mixture and
for adjusting the concentration of oxygen in the mixture with a precision of 60.1 %, by volume, of the gas mixture, when the gas
velocity through the chimney is 40 6 2 mm/s at 23 6 2°C.
6.3.1 The system for direct gas measurement and control involves needle valves on individual and mixed gas supply lines, a
paramagnetic oxygen analyzer that continuously samples the mixed gas, and a flow meter to indicate when the gas flow through
the chimney is within the required limits. See Annex A4 for an alternate system for gas measurement.
D2863 − 23
FIG. 2 Frame Design
FIG. 3 Rod with a Slit
D2863 − 23
6.3.2 An alternate system for gas measurement is described in Annex A4. The system used for indirect gas measurement (Annex
A4) requires calibration after assembly to ensure that the compounded errors of the component parts do not exceed the
requirements of 6.3.
6.3.3 Means shall be provided for checking or ensuring that the temperature of the gas mixture entering the chimney is 23 6 2°C.
If this involves an internal probe, its position and profile shall be designed to minimize induction of turbulence within the chimney.
6.4 Flame Igniter. The flame igniter shall comprise a tube, with an inside diameter of 2 6 1 mm, that can be inserted into the
chimney to apply the test flame.
6.4.1 The fuel supply shall be adjusted so that the flame height is 16 6 4 mm (measured from the bottom of the flame to the top
of the flame) when the flame igniter tube is vertical within the chimney and the flame is burning within the chimney atmosphere
(see Fig. 4).
6.4.2 The flame fuel shall be one of the following: methane, or natural gas of at least 97 % purity, or propane of at least 98 %
purity. The flame fuel shall have no premixed air.
6.5 Timing Device. A timing device shall be provided, which is capable of measuring periods up to 5 min with an accuracy of 60.5
s.
6.6 Fume Extraction System. A fume extraction system shall be provided with sufficient ventilation or exhaust to remove fumes
or soot expelled from the chimney without disrupting the gas-flow rate or temperatures in the chimney.
NOTE 4—If soot-generating materials are being tested, it is likely that the glass chimney, gas inlets, and inlet screen will require cleaning between tests
to maintain good visibility and to function properly.
6.7 Gas Supplies. The gas supplied to the test apparatus shall consist of pressurized sources of oxygen or nitrogen, or both, not
less than 98 % pure or clean dry air, or both, (containing 20.9 % oxygen), as appropriate.
FIG. 4 Oxygen Index Apparatus Schematic Showing Igniter Flame Detail
D2863 − 23
6.7.1 The gas mixture entering the chimney shall have a moisture content of <0.1 %, unless the results have been shown to be
insensitive to higher moisture levels in the gas mixture. The gas supply system shall incorporate a drying device, or provision for
monitoring or sampling the gas supply for moisture content, unless the moisture content of the gas supplies is known to be
acceptable.
NOTE 5—It must be noted that bottled oxygen or nitrogen will not always contain <0.1 % of water; moisture contents of 0.003 to 0.01 % are typical for
commercial supplies as filled bottles >98 % pure, but as such bottled gases are depressured to below about 1 MPa, the moisture content of the gas drawn
off has been found to rise above 0.1 %.
7. Test Specimens
7.1 General:
7.1.1 The specimens shall be die-punched, cut by hand using a razor blade or other sharp tool, or cut by an automatic machine.
Alternatively, specimens shall be prepared directly by injection molding.
7.1.2 Ensure that the surfaces of the specimens are clean and free from flaws that could affect burning behavior, for example,
peripheral molding flash or burrs from machining. The edges of the specimens shall be smooth and free from fuzz or burrs of
material left from machining or molding.
7.1.3 Record the position and orientation of the test specimens with respect to any asymmetry in the sample material (see Note
6).
NOTE 6—Oxygen index results are likely to be significantly affected by differences in burning behavior, due to material inhomogeneity (for example,
different levels of shrinkage when heated for specimens cut in different directions from asymmetrically-oriented thermoplastics film).
7.1.4 The test specimens shall conform to the dimensions and geometry listed in Table 1. If non-standard size specimens are used,
a difference in oxygen index is likely to result.
7.1.5 It is likely that, for materials where the oxygen index is known to within 62 % by volume, 15 test specimens will be
sufficient. However, for materials of unknown oxygen index, or which exhibit erratic burning characteristics, between 15 and 30
test specimens are likely to be required.
7.2 Self-Supporting Specimens (Specimen Types I, II, III, and IV)
7.2.1 The specimens shall be prepared in accordance with 7.1.
7.3 Specimens of Flexible Sheet or Film Materials that Require Support (Specimen Type IV)
7.3.1 The specimens shall be prepared in accordance with 7.1 and they shall be supported by both vertical edges in a frame
equivalent to that illustrated by Fig. 2 (see 6.2.2).
7.4 Self-Supporting Specimens Rolled from Thin Films (Specimen Type VI)
7.4.1 For preparation of Type VI specimens, use the rolling tool described in 6.2.3.
7.4.2 Specimen films shall be prepared in accordance with 7.1.
7.4.3 Insert one corner of the film into the slit of the thin film rolling tool and then wind the film around the rod in a spiral of 45°,
as shown in Fig. 3. Ensure that the 45° angle is maintained during the winding process so that the film reaches exactly to the end
of the tool, to produce a test piece of the correct length. After the winding is finished, tape the last end of the roll while the material
is still on the stainless steel rod to prevent loosening. Then pull the rod out of the rolled film.
7.4.4 Cut off the rolled film at a distance of 20 mm from the top end. See Fig. 5.
7.5 Specimen Marking
D2863 − 23
FIG. 5 Rolled Film
7.5.1 For monitoring the distance over which burning occurs, mark the specimen with transverse lines at one or more levels which
are dependent upon the specimen form and the ignition procedure to be used. Structurally self-supporting specimens shall be
marked on at least two adjacent faces. If wet inks are used, ensure that the marks are dry before the specimen is ignited.
7.5.2 If test specimens of Type I, II, III, IV, or VI are to be tested in accordance with Procedure A, they shall be marked 50 mm
from the end to be ignited. If specimens of Type I, II, III, IV, and VI are to be tested in accordance with Procedure B, they shall
be marked at 10 mm and at 60 mm from the end to be ignited.
7.5.3 The reference marks for testing specimens of Type V are carried by the supporting frame (see Fig. 2), but thermally stable
materials shall additionally be marked at 20 mm and at 100 mm from the end to be ignited, for convenience.
7.6 For cellular materials, the density shall be determined in accordance with Test Method D1622.
NOTE 7—It is possible that the oxygen index samples of cellular materials that contain volatile flammable blowing agents that diffuse from the sample
will change with time.
8. Conditioning
8.1 Unless otherwise specified, each test specimen shall be conditioned for at least 40 h at 23 6 2°C and 50 6 5 % relative
humidity (RH) immediately prior to use in accordance with Practice D618.
8.2 Maintain the ambient conditions for the test apparatus at 23 6 5°C. Keep the test specimens in an enclosure at 23 6 2°C and
50 6 5 % RH and take the test specimens out of the enclosure just before testing (so that testing is conducted within 30 minutes
of the test specimen removal from the conditioning environment).
9. Calibration of Apparatus
9.1 Calibration for systems with direct oxygen gas concentration measurement. Calibrate the system for direct oxygen gas
concentration measurement with a paramagnetic oxygen analyzer, used for the measurements in 6.3.1, by the following: (a) turning
the nitrogen flow on and closing the oxygen flow and confirming that the oxygen concentration on the display reads 0.0 %, and
(b) turning the oxygen flow on and closing the nitrogen flow and confirming that the oxygen concentration on the display reads
the same value as the concentration of oxygen in the supply gas (see 6.7).
9.2 Calibration for systems using indirect gas measurement in accordance with Annex A4. Calibrate the flow-measuring system
used for the indirect measurements of oxygen concentration and flow rate with the instrumentation in 6.3.2 using a water-sealed
rotating drum meter (wet test meter) in accordance with Test Method D1071 or by equivalent calibration devices. The maximum
interval between recalibration shall be six months.
9.3 A cast PMMA specimen shall be used as a verification material at least once a month. See Annex A1 for calibration method.
D2863 − 23
10. Hazards
10.1 The exhaust system must be so designed and operated that the laboratory environment is protected from smoke and gases
or vapors. The operator shall be instructed on ways to minimize exposure to combustion products by following sound safety and
industrial hygiene practices. For example, ensure that the exhaust system is working properly and wear appropriate clothing
including gloves, safety glasses, breathing apparatus (when hazardous fumes are expected).
10.2 During this test, high temperatures are generated that are capable of igniting some clothing following even brief exposures.
Precautions shall be taken to avoid ignitions of this type.
11. Symbols and Criteria for This Test Method
11.1 Test Method Criteria:
11.1.1 The criteria for oxygen index measurements are described in Table 2.
11.1.2 The extent of burning in this test method is considered to have been exceeded when any part of the visibly burning portion
of a specimen, including burning drips descending the vertical faces, passes the level indicated in the column.
11.1.3 The criteria in Table 2 do not necessarily produce equivalent oxygen index results for specimens of differing shape or tested
using different ignition conditions or procedures.
11.2 Method Symbols:
11.2.1 C —oxygen concentration in percent volume.
o
11.2.2 C —final value of oxygen concentration in percent volume.
F
11.2.3 C —each of the oxygen concentration percentages used during measurement of the last six responses in the N series.
i T
11.2.4 O—neither the period or extent of burning exceeds the relevant limit specified in Table 2.
11.2.5 X—the period or extent of burning exceeds the relevant limit specified in Table 2.
11.2.6 N —series of “X” or “O” results.
L
11.2.7 N —series of “X” or “O” results plus five (N = N + 5).
T T L
11.2.8 σ*—standard deviation of the oxygen concentration.
A
TABLE 2 Criteria for Oxygen Index Measurements
Alternative Criteria
Period of
Test Specimen
Ignition Procedure Burning
B
Type (See Table 1) Extent of Burning
After
Ignition(s)
I, II, III, IV, and VI A 180 50 mm below the top
(top surface ignition) of the specimen
I, II, III, IV, and VI B 180 50 mm below the
(propagating ignition) upper reference
mark
V propagating ignition 180 80 mm below the
upper reference
mark (on the frame)
A
The criteria in this table do not necessarily produce equivalent oxygen index
results for specimens of differing shape or tested using different ignition conditions
or procedures.
B
The extent of burning is exceeded when any part of the visibly burning portion of
a specimen, including burning drips descending the vertical faces, passes the level
indicated in the column.
D2863 − 23
11.2.9 d—interval between oxygen concentration levels in percent volume.
11.2.10 k—a factor to be determined from Table 3.
11.2.11 n—number of measurements of oxygen concentration.
12. Test Procedure
NOTE 8—Some materials exhibit a non-flaming type of combustion (for example, glowing combustion) instead of, or at a lower oxygen concentration
than that required for, flaming combustion. When testing such materials, it is necessary to identify the type of combustion for which the oxygen index
is required or measured.
12.1 Procedure A
12.1.1 Select an initial concentration of oxygen to be used. Whenever possible, base the initial concentration on experience of
results for similar materials. Alternatively, try to ignite a test specimen in air, and note the burning behavior. If the specimen burns
rapidly, select an initial concentration of about 18 % oxygen; if the test specimen burns gently or unsteadily, select an initial oxygen
concentration of about 21 %; if the specimen does not continue to burn in air, select an initial concentration of at least 25 %,
depending upon the difficulty of ignition or the period of burning before extinguishing in air.
12.1.2 Record the oxygen concentration used as the volume percent measured by an oxygen paramagnetic analyzer (if present)
or as the volume percent calculated in accordance with the equations given in Annex A2 (if the system described in 6.3.2 is used).
12.1.3 Ensure that the test chimney is vertical (see Fig. 1). Verify that the temperature at the lower end of the chimney is at least
23 6 2°C.
12.1.4 Mount a specimen vertically in the center of the chimney so that the top of the specimen is at least 100 mm below the open
top of the chimney and the lowest exposed part of the specimen is at least 100 mm above the top of the gas distribution device
at the base of the chimney (see Fig. 1 or Fig. 2, as appropriate, for guidance).
12.1.5 Set the gas mixing and flow controls so that an oxygen/nitrogen mixture at 23 6 2°C, containing the desired concentration
of oxygen, is flowing through the chimney at a rate 40 6 2 mm/s. Let the gas flow purge the chimney for at least 30 s prior to
ignition of each specimen, and maintain the flow without change during ignition and combustion of each specimen.
12.1.6 For specimen Types I, II, III, IV, and VI, use top surface ignition, as described in 12.1.8.
12.1.7 For tests on materials that exhibit steady burning and spread of combustion in oxygen concentrations at, or close to, their
TABLE 3 Determination of k
1 2 3 4 5 6
Values of k for which the first N determinations are:
Responses for the Last Five L Responses for the Last Five
A
Measurements Measurements
(a) O OO OOO OOOO
XOOOO −0.55 −0.55 −0.55 −0.55 OXXXX
XOOOX −1.25 −1.25 −1.25 −1.25 OXXXO
XOOXO 0.37 0.38 0.38 0.38 OXXOX
XOOXX −0.17 −0.14 −0.14 −0.14 OXXOO
XOXOO 0.02 0.04 0.04 0.04 OXOXX
XOXOX −0.50 −0.46 −0.45 −0.45 OXOXO
XOXXO 1.17 1.24 1.25 1.25 OXOOX
XOXXX 0.61 0.73 0.76 0.76 OXOOO
XXOOO −0.30 −0.27 −0.26 −0.26 OOXXX
XXOOX −0.83 −0.76 −0.75 −0.75 OOXXO
XXOXO 0.83 0.94 0.95 0.95 OOXOX
XXOXX 0.30 0.46 0.50 0.50 OOXOO
XXXOO 0.50 0.65 0.68 0.68 OOOXX
XXXOX −0.04 0.19 0.24 0.25 OOOXO
XXXXO 1.60 1.92 2.00 2.01 OOOOX
XXXXX 0.89 1.33 1.47 1.50 OOOOO
A
Values of k for which the first N determinations are (b) X, XX, XXX, a
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