What is the limiting oxygen index determined to test the efficiency?

The limiting oxygen index (LOI) is a measure of the minimum concentration of oxygen, expressed as a percentage, that will support the combustion of a material. It is determined by exposing a vertically mounted specimen of the material to a mixture of oxygen and nitrogen gases in a combustion chamber, and gradually reducing the oxygen concentration until the material stops burning. The LOI is then calculated as the percentage of oxygen in the gas mixture at which the material stops burning.

The LOI test is commonly used to evaluate the fire safety of materials, particularly in the plastics industry. Materials with a high LOI are considered to be more flame retardant, as they require a higher concentration of oxygen to sustain combustion. Conversely, materials with a low LOI are more flammable and pose a greater fire hazard.