What is the oxygen index test?

What is the oxygen index test?

Oxygen concentration values are known as the Oxygen Index (OI) or, historically, the Limiting Oxygen Index (LOI). The oxygen concentration is measured using a paramagnetic oxygen analyzer and is controlled by varying the relative flow of oxygen and nitrogen through a vertical glass column. Specimens are supported vertically inside the glass column, and an ignition source is then placed in contact with the top edge of the specimen and withdrawn.

If “ignition” occurs, as defined differently by the standard for varying types of materials, then the oxygen concentration in the column is reduced for the next specimen. If the ignition is unsuccessful, the oxygen concentration is increased for the next specimen. This systematic approach continues until the lowest oxygen concentration is determined that will support the combustion of the material.

The lower the Limiting Oxygen Index, the greater the propensity of that material to ignite and burn. For example, materials with established Oxygen Indices lower than 20.9% will continue to burn in normal atmospheric air, after an ignition source has been removed.

Definition of oxygen index:

When a mixture of oxygen and nitrogen at 23°C±2°C is introduced, the minimum oxygen concentration that just maintains the combustion of the material is expressed in volume fraction.

EN ISO 4589-2 test principle:

Fix a sample vertically in a transparent combustion tube with upwardly flowing oxygen and nitrogen mixed gas, ignite the top of the sample, observe the combustion characteristics of the sample, and compare the continuous burning time or length of the sample with the given criterion , Estimate the minimum oxygen concentration through a series of samples at different oxygen concentrations.

EN ISO 4589-2 oxygen index test data requirements:

Different risk levels have different requirements for oxygen index test data

EN ISO 4589-2 oxygen index test sample size requirements:

150mm*6.5mm*3mm

Or 140mm*52mm* thickness