Oxygen index

The oxygen index, also known as the Lowest Oxygen Index (LOI), is a measure of the oxygen concentration in a mixture of oxygen and nitrogen that is required for a material to start burning. This index indicates how much oxygen must be present at a minimum for a specific material to catch fire.

The oxygen index is measured in accordance with ISO 4589 by supplying a burning sample of the material with a mixture of oxygen and nitrogen with a decreasing oxygen content until the flame goes out. This process makes it possible to determine at which oxygen proportion the material is no longer combustible.