Here are more details on the specific test procedures for ASTM D2863 and ISO 4589-2:

1. ASTM D2863:

   - Sample Preparation: The sample, typically in the form of a bar or plaque, is conditioned to the desired temperature and humidity.

   - Test Setup: The sample is placed vertically in a combustion chamber, and the chamber is purged with a flow of oxygen-enriched gas.

   - Ignition: The sample is ignited at the bottom using a suitable ignition source, such as a flame or spark.

   - Oxygen Concentration Variation: The oxygen concentration within the chamber is gradually reduced by introducing a flow of nitrogen or other inert gas while maintaining a constant flow rate.

   - Observation: The progress of the combustion is observed, and the oxygen concentration at which the sample stops burning is recorded.

   - Calculation: The limiting oxygen index (LOI) is calculated as the percentage of oxygen concentration at extinction.

2. ISO 4589-2:

   - Sample Preparation: The sample is conditioned according to specified temperature and humidity conditions.

   - Test Setup: The sample is placed vertically in a combustion chamber, and the chamber is purged with a flow of oxygen-enriched gas.

   - Ignition: The sample is ignited at the top using a suitable ignition source, such as a flame or spark.

   - Oxygen Concentration Variation: The oxygen concentration within the chamber is gradually reduced by introducing a flow of nitrogen or other inert gas while maintaining a constant flow rate.

   - Observation: The progress of the combustion is observed, and the oxygen concentration at which the sample stops burning is recorded.

   - Calculation: The limiting oxygen index (LOI) is calculated as the percentage of oxygen concentration at extinction.

It's important to note that while the overall principles of the tests are similar, there might be some variations in the specific test parameters, such as sample dimensions, conditioning conditions, and ignition sources, between ASTM D2863 and ISO 4589-2. It is recommended to refer to the respective standards for precise and detailed test procedures.

Please keep in mind that my knowledge cutoff is in September 2021, and there might have been updates or revisions to these standards since then. It's always advisable to consult the latest versions of the standards for accurate and up-to-date information.