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Frequently Asked Questions | FAQs
What do you mean by limiting oxygen index?
The Limiting Oxygen Index (LOI) is a measure of the minimum concentration of oxygen in a mixture of oxygen and nitrogen that will support the combustion of a material. It is commonly used as an indicator of the flammability of materials, particularly polymers.
LOI is expressed as a percentage, and it represents the minimum volume fraction of oxygen required to sustain combustion. For example, an LOI of 21% means that a material requires at least 21% oxygen concentration in the surrounding environment to continue burning.
LOI is determined through a standardized test, such as ASTM D2863 or ISO 4589-2, where a test specimen is exposed to a flowing mixture of oxygen and nitrogen at various concentrations, and the minimum oxygen concentration that supports sustained combustion is recorded as the LOI value.
Materials with higher LOI values are considered less flammable, as they require higher oxygen concentrations to support combustion. Conversely, materials with lower LOI values are more flammable, as they can continue to burn with lower oxygen concentrations.
LOI is used in various industries, such as aerospace, automotive, and electronics, to assess the fire safety of materials and make informed decisions on their suitability for specific applications. Materials with higher LOI values are preferred in applications where fire resistance is critical, while materials with lower LOI values may require additional fire protection measures or may not be suitable for certain applications.