Standard Introduction
JIS K 7201-3 specifies the method for determining the minimum oxygen concentration in a mixed gas of oxygen and nitrogen when the vertical small sample is maintained in combustion at a temperature of 25 ° C - 150 ° C and under specified test conditions. JIS K 7201-3 is applicable to rod or sheet materials that can stand independently at the test temperature and have a thickness of up to 10.5mm.

Scope of application
JIS K 7201-3 is applicable to solid materials, laminated materials or foamed materials with an apparent density of more than 100kg/m³.

Test method
A small sample is vertically supported in the oxygen-nitrogen mixed gas flowing upward in a transparent combustion cylinder. Ignite the upper end of the sample, observe the subsequent combustion behavior of the sample, and compare the combustion duration or length of the sample with the limit value specified for that combustion. The minimum oxygen concentration was determined by conducting tests on a series of samples by changing the oxygen concentration.

Basis for judgment
During the testing process, whether the sample is on fire, the burning time and the burning length are measured, and the minimum oxygen concentration required for continued combustion is determined as the oxygen index.