ASTM D2863 : 08

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

Standard Details

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 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazards statement are given in Section 10.

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.

TABLE 1 Test Specimen Dimensions

Test Specimen Type^A		Dimensions			Material Form
Test Specimen Type^A		Length, mm	Width, mm	Thickness, mm	Material Form
	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
	III^B	80 to 150	10 ± 0.5	≤ 10.5	for sheet materials
	IV^C	70 to 150	6.5 ± 0.5	3 ± 0.25	alternative size for self-supporting molding or sheet materials
	V^B	140 ± 5	52 ± 0.5	≤10.5	for flexible film or sheet
	VI^B^D	140 to 200	20	0.02 to 0.10	for thin film; limited to film 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 StandardDetails.

^C The Type IV (ASTM) specimen will eventually be discontinued in favor of the Type 1 (ISO) specimen.

^D 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.