How Does a Limiting Oxygen Index Tester Evaluate the Fire Resistance of Materials?

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.

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.

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

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 Advantages

The core advantages of the Limiting Oxygen Index (LOI) Tester lie in its high-precision quantitative evaluation, efficient and convenient operation, and strong standard compatibility. It provides accurate test data to support material development, flame-retardant performance optimization, and fire safety control.

Core Performance Advantages

1. High-Precision Measurement

The tester can accurately control the ratio of oxygen and nitrogen in the test gas mixture. The oxygen concentration adjustment accuracy can typically reach ±0.1%, ensuring precise and reliable measurement of the critical oxygen concentration required for material combustion.

This high-precision control enables accurate evaluation of the flammability characteristics and oxygen sensitivity of different materials.

2. Quantitative Performance Evaluation

The Limiting Oxygen Index (LOI) converts the abstract concept of “fire resistance capability” into a specific numerical value expressed as a volume percentage of oxygen concentration.

A higher LOI value indicates that the material requires a higher oxygen concentration to sustain combustion, meaning the material is more difficult to ignite and generally has better flame-retardant performance.

This quantitative evaluation method allows direct comparison between different materials and provides objective criteria for material selection.

3. High Level of Automation

Modern LOI testers are generally equipped with digital sensors and computer-based control systems, enabling automatic gas mixing, real-time data display, and precise monitoring of test conditions.

The automated operation significantly reduces human reading errors, improves testing efficiency, and enhances the repeatability and reliability of test results.

Application and Economic Advantages

1. Wide Industry Applicability

The Limiting Oxygen Index Tester complies with international standards such as ISO 4589-2 and ASTM D2863 and is widely applicable for evaluating the combustion characteristics of various materials, including:

Plastics

Textiles

Rubber materials

Foam materials

Polymer composites

Its broad applicability makes it an important testing tool for material manufacturers, research institutions, and quality inspection organizations.

2. Efficient Support for Material Development

The tester helps engineers quickly evaluate the influence of different formulations and processing technologies on flame-retardant performance during laboratory research stages.

By analyzing changes in LOI values after adjusting material formulations or adding flame-retardant agents, manufacturers can optimize product designs, improve fire safety performance, and shorten the product development cycle.

Conclusion

The Limiting Oxygen Index Tester provides a scientific and reliable method for evaluating the flame-retardant performance of materials. Through precise oxygen concentration control, quantitative combustion assessment, and standardized testing procedures, it offers essential technical support for new material development, fire safety evaluation, quality control, and compliance testing across multiple industries.

FAQ

(1) What is this product?

An instrument that measures the minimum oxygen concentration required to sustain combustion of solid materials.

(2) What is this product used for?

To determine flame-retardant performance of plastics, textiles, rubber, foam, film, and wood under controlled oxygen-nitrogen conditions.

(3) What is the working principle of this product?

A sample is placed in a transparent cylinder, exposed to a controlled O₂/N₂ mixture, ignited at the top, and the oxygen level is adjusted to determine the LOI.

(4) Why is this product important?

It allows manufacturers and labs to evaluate material flammability accurately, ensuring compliance with safety standards.

(5) Which industries is this product suitable for?

Plastics, textiles, rubber, foam, film, wood, fire research labs, quality inspection agencies, and manufacturing quality control.