What is limiting oxygen index test equipment?

The Limiting Oxygen Index Tester measures the minimum oxygen concentration needed to sustain combustion of solid materials like textiles and plastics. Samples are fixed vertically in a transparent cylinder with an oxygen-nitrogen mixture, ignited at the top, and observed for combustion characteristics. By comparing burn time or length against limits, the ultimate oxygen index is determined, offering an efficient, user-friendly method for material research and quality control.

Standards

GBT 2406.1 Plastics Test of burning behaviour by oxygen index-Part 1: guideline;

GBT 2406.2 Plastics Test of burning behaviour by oxygen index -Part 2: Indoor-temperature test;

GBT 5454 Textiles Performance test of burning by oxygen index;

GBT 10707 Rubber Performance test of burning behaviour;

ISO 4589-2 Plastics Test of burning behaviour by oxygen index -Part 2: Indoor-temperature test;

ASTM -- D2863 Standard Test Method for Measuring the Minimum Oxygen Concentration of material combustion which is similar to plastics material (Oxygen Index);

IS0 4589-3 (Please inquire separately for the apparatus for the

ISO 4589-2  " Plastics -- Determination of burning behaviour by oxygen index -- Part 2: Ambient-temperature test”

NES 714. EN 45545-2.JIS 7201. BS 2782. etc.,

Features

Imported sensors

Imported Paramagnetic oxygen concentration sensor with high precision and stable performance.Real-time detection of oxygen concentration with PLC precise control so that can adjust the oxygen concentration through the airflow.

Flexible fixture design

The fixture is made of refractory and stainless material, which can resist high temperature and rust.It can hold various samples.By replacing the sample holder, the sample requirements of different characteristics can be fulfilled.

Linited Oxygmn Indes Testet

Intelligent touch operation 7-inch color screen, intelligent touch, multi-touch operating system, convenient operation, multi-language display, switching between

Chinese and English.Simplified operation interface, easy to operate

Quick change structural design

The test tube of this instrument which is made of high temperature resistant transparent glass combing with the base adopts quick change design to clearly observe the combustion situation in the test. Moreover, it is easy to clean after the test. The stainless steel base can avoid the influence of various corrosion on the test data, and its service life is long.

Parameters

Application

This instrument measures the minimum oxygen volume percentage concentration at just required for maintaining combustion of the polymer.it is suitable for a wide range of materials by changing the sample fixture used in a variety of mechanical properties of the sample.lt can be used for the determination of burning performance of plastics, rubber, fiber, foam, film, textile and wood.

It is applicable to the performance verification of new products, quality control of the production department, and the of material properties for the third-party testing organization, the product performance verification laboratory, and the quality and technical supervisiondepartment, etc.

Test Procedure

Install the sample and adjust the burner angle.

Adjust the O₂/N₂ flow rate to the initial concentration (e.g., 18% or 25%).

Ignite the sample and record the burning time or flame front position.

Adjust the oxygen concentration based on the burning behavior, and repeat the test until the accuracy requirements are met (the difference between three test results < 0.5%).

Result Analysis: Calculate the average of the three oxygen concentrations to determine the LOI value of the material.

Safety Precautions

Personal Protective Equipment: Operators must wear safety glasses and gloves to avoid injury from smoke or flames.

Gas Management:

The purity of the oxygen cylinder must be calibrated regularly, and the nitrogen cylinder pressure should not be less than 1MPa.

Adjust the flow rate evenly to avoid sudden changes in gas pressure.

Equipment Maintenance:

Regularly clean the combustion tube and igniter, and remove combustion residue.

If any problems occur, please contact professional personnel for repair; do not disassemble components yourself.

Ventilation Requirements: The test must be conducted in a fume hood to prevent the accumulation of exhaust gases.

Maintenance Information

(1) Clean the combustion tube and igniter regularly to remove residue.

(2) Inspect oxygen and nitrogen cylinders for proper pressure and purity.

(3) Avoid disassembling critical components; contact professional personnel for repairs.

(4) Ensure proper ventilation to avoid accumulation of exhaust gases.

Core Functions and Roles of the Limiting Oxygen Index Tester

The Limiting Oxygen Index (LOI) Tester is mainly used to determine the minimum oxygen concentration required to just sustain combustion of a material in an oxygen–nitrogen mixed gas stream. By providing quantitative results, it evaluates the flammability and flame-retardant rating of materials, making it a core instrument in polymer research, fire safety engineering, and quality inspection.

Core Functions and Applications

Evaluation of Flame Retardancy:

The instrument quantifies the combustibility of a material by measuring its limiting oxygen index (LOI). A lower LOI value indicates that the material is more flammable, while a higher LOI value indicates better flame resistance.

Material Classification and Grading:

In general, materials can be classified as follows:

LOI < 21%: flammable materials

LOI 22%–27%: combustible materials

LOI > 28%: difficult-to-burn (flame-retardant) materials

Formulation and Development Support:

During the development of plastics, rubber, textiles, and cable materials, researchers use the LOI tester to evaluate the effect of different flame retardant formulations and optimize additive ratios to improve fire resistance performance.

Quality Control in Production:

It is widely used for raw material inspection and final product fire safety evaluation in production lines, ensuring compliance with fire safety standards in industries such as aerospace, construction, automotive, and electrical and electronics.

Conclusion

The Limiting Oxygen Index Tester provides accurate, repeatable measurement of the minimum oxygen concentration required for combustion, supporting research, quality control, and regulatory compliance for plastics, textiles, rubbers, and other materials.