What is the test method for limiting oxygen index?

The Limiting Oxygen Index (LOI) test is a standard method used to determine the minimum concentration of oxygen required to support combustion of a material. It is commonly used to evaluate the flammability characteristics of various materials. 

In the LOI test, a sample of the material is exposed to a controlled flow of oxygen-enriched gas. The sample is placed vertically in a glass chimney and ignited at the top. The oxygen concentration within the chimney is gradually decreased by flowing nitrogen or another inert gas. 

The sample's surface is continuously monitored for ignition and combustion. The oxygen concentration at which the material stops burning and self-extinguishes is recorded as the LOI value. This value is expressed as a percentage, representing the minimum oxygen concentration required to support combustion.

The LOI test provides valuable information about a material's flammability and its ability to resist ignition and self-extinguish. It is commonly used in industries such as aerospace, automotive, and construction to assess the fire safety properties of various materials, including polymers, textiles, and composites.