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Limiting oxygen index

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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. [1]


LOI values for different plastics are determined by standardized tests, such as the ISO 4589 and ASTM D2863.[2]

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

References

  1. ^ Definition taken from Principles of Polymer Engineering (2nd edition) by N.G. McCrum , C.P. Buckley, and C.B. Bucknall
  2. ^ ASTM D 2863, Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index).
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