Limiting oxygen index: Difference between revisions

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The '''limiting oxygen index (LOI)''' is the minimum concentration of [[oxygen]], expressed as a percentage, that will support [[combustion]] of a [[polymer]]. It is measured by passing a mixture of oxygen and [[nitrogen]] over a burning specimen, and reducing the oxygen level until a critical level is reached. <ref>Definition taken from Principles of Polymer Engineering (2nd edition) by N.G. McCrum , C.P. Buckley, and C.B. Bucknall</ref>

LOI values for different plastics are determined by standardized tests, such as the ISO 4589 and ASTM D2863.<ref>[[ASTM]] D 2863, ''Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index).''</ref>

The LOI value is also depended on surrounding temperature of the sample. The % of Oxygen required for combustion reduces as the surrendering temperature is increased.

Plastics and Cable material is tested for their LOI value at both ambient temperature and elevated temperature to understand their oxygen requirement under actual fire conditions.

Materials which have minimum Oxygen % requirement for burning more then atmospheric Oxygen are called Fire Retardant material.

==See also==