The Oxygen Index (OI) test is a commonly used laboratory test to measure the flammability of materials. It is used primarily in the plastics industry to determine the fire safety of different plastic materials. The test measures the minimum concentration of oxygen in a mixture of oxygen and nitrogen that is required to support combustion of a material.
During the test, a small sample of the material to be tested is held vertically in a combustion chamber, and a mixture of oxygen and nitrogen is slowly introduced into the chamber. The concentration of oxygen in the mixture is gradually reduced until the material either stops burning or continues to burn at a very slow rate. The OI value is then calculated as the percentage of oxygen in the mixture at which the material just stops burning.
The OI value is an important indicator of the fire safety of a material. A material with a high OI value requires a higher concentration of oxygen to support combustion, making it less flammable than a material with a lower OI value. The OI value is also used to compare the fire safety of different materials, and to determine whether a material meets certain fire safety standards.
It is important to note that the OI test is just one of many tests used to evaluate the fire safety of materials, and should be used in conjunction with other tests and evaluations to determine the overall fire safety of a material.