The Limiting Oxygen Index (LOI) is a measure of the minimum concentration of oxygen, expressed as a percentage, that will support combustion of a material. It is determined by exposing a vertical sample of the material to a mixture of oxygen and nitrogen and measuring the concentration of oxygen required to maintain combustion.
The LOI test is commonly used to evaluate the fire safety of materials, particularly polymers and other organic materials. The test measures the inherent fire resistance of a material, and materials with a higher LOI are generally considered to be more fire-resistant. Thus, the LOI test is an important tool for evaluating the fire safety of materials used in a wide range of applications, including building and construction materials, automotive components, textiles, and electronics.
In general, materials with an LOI value of 21 or higher are considered to be self-extinguishing and are classified as difficult to ignite. Materials with an LOI value below 21 are considered to be more flammable and may require additional fire-retardant treatments or coatings to improve their fire safety performance.
It is important to note that the LOI test is just one of many tests used to evaluate the fire safety of materials, and its results should be considered in conjunction with other fire safety tests and standards. Additionally, the LOI test is a laboratory test and may not directly reflect the fire behavior of a material under real-world conditions.