Limiting Oxygen Index (LOI) Test

The limiting oxygen index (LOI) is a measure of the lowest percentage of oxygen in the oxygen/nitrogen mixture required to support the combustion of plastics. The limiting oxygen index (LOI) test is a widely used research and quality control tool to detect the relative flammability of polymeric materials.

The standards based on the limiting oxygen index (LOI) tests are:

• ISO 4589-2 Plastics - Determination of combustion behavior with oxygen index - Part 2: Ambient temperature testing
• ASTM D2863-19 Standard test method for measuring the minimum oxygen concentration to promote wax burning of plastics (oxygen index)

The ISO 4589-2 standard defines test methods for determining the minimum volume fraction of oxygen in mixture with nitrogen that will support combustion of small vertical test specimens under specified test conditions. Results are defined as oxygen index (OI) values. This standard contains methods for testing self-supporting materials in the form of vertical bars or sheets up to 10,5 mm thick. These methods are suitable for solid, layered or cellular materials characterized by an apparent density of 100 kg/m3 or more. The methods can also be applied to some cellular materials that have a less apparent density.

ASTM D2863-19 is a fire-test-response standard that includes three test methods for measuring the minimum oxygen concentration, expressed as a percentage by volume, that would support flaming combustion in a flowing mixture of oxygen and nitrogen:

• Procedure A includes surface ignition.
• Procedure B includes propagated ignition.
• Procedure C involves comparing with a certain minimum value of the oxygen index.

This test method allows testing structurally self-supporting materials in the form of vertical bars or sheets up to 10.5 mm thick. Such materials are solid, laminated or cellular materials characterized by an apparent density greater than 15 kg/m3. This test method also allows testing flexible sheet or film materials while being supported vertically. This test method is also suitable, in some cases, for cellular materials with an apparent density of less than 15 kg/m3.

Our organization also provides limiting oxygen index (LOI) testing services with its trained and expert staff and advanced technological equipment, among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors.