ISO 4589-2: Burning behavior by oxygen index

The ISO 4589-2 oxygen index test is used to evaluate the fire behavior of certain railway materials according to the EN 45545-2 standard. It is required to meet requirements R22, R23, and R24, which apply to products such as insulators, seals, pipes, and hoses.

The oxygen index (OI) is the minimum volume-based percentage of oxygen in an oxygen-nitrogen mixture required to support the combustion of the sample under specified conditions. For a material to meet EN 45545-2 requirements, the OI must be at least 28% (hazard classes HL1 and HL2) or at least 32% (HL3).

Testing is performed on 20 replicate samples, with the required specimen size depending on the material:

• 80−150 mm x 10 mm x 4 mm for mould-made materials, such as plastics

• 80−150 mm x 10 mm x 10 mm for porous materials, such as foams

• 140 mm x 52 mm x d, where d < 10.5 mm, for flexible films, sheets, and fabrics