How to measure limiting oxygen index?

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.

Advantages of the Limiting Oxygen Index (LOI) Tester

In the field of material flammability and flame-retardancy testing, the Limiting Oxygen Index (LOI) Tester is an indispensable instrument. With its unique technical features and significant advantages, it has become an essential tool for research institutions, testing laboratories, and industrial quality control departments.

1. High-Precision Measurement Capability

The LOI tester adopts advanced sensor technology and a highly accurate gas flow control system, enabling precise regulation and measurement of oxygen–nitrogen gas mixtures. During testing, the instrument can monitor real-time changes in gas concentration within the combustion chamber and automatically adjust oxygen levels based on the burning behavior of the specimen, ensuring high accuracy and repeatability of results.

In addition, the device is equipped with a high-precision timing system that accurately records combustion time, providing comprehensive data support for evaluating the flame-retardant performance of materials.

2. Wide Applicability

Different materials exhibit different combustion characteristics, and the LOI tester is capable of meeting a broad range of testing requirements. It can be used for soft materials such as plastics, rubber, and textiles, as well as harder materials such as wood and metal composites.

Furthermore, the instrument allows flexible adjustment of test parameters according to different standards and requirements, including gas flow rate, specimen dimensions, and ignition methods, making it suitable for diverse and customized testing needs.

3. Easy Operation and High Automation

Modern LOI testers are typically equipped with intuitive control interfaces and user-friendly human–machine interaction systems. Operators only need to follow on-screen instructions to complete setup and testing procedures.

The instrument features automatic ignition, automatic gas concentration adjustment, and automatic data recording, significantly reducing manual intervention and improving testing efficiency. It also supports data storage and retrieval functions, facilitating result management and analysis.

4. Safe and Reliable Design

During combustion testing, high temperatures, smoke, and potentially harmful gases may be generated, posing risks to operators. The LOI tester is designed with safety in mind. The combustion chamber provides excellent thermal insulation and an efficient exhaust system to reduce heat and smoke concentration in the testing environment.

It is also equipped with an emergency stop button and multiple safety protection mechanisms. In case of abnormal conditions, the system can immediately cut off power and gas supply to ensure operator safety.

5. Compliance with International Standards

The design and manufacturing of the LOI tester strictly comply with international standards such as ISO 4589 “Plastics — Determination of burning behaviour by oxygen index”. The test results are internationally recognized, providing reliable data support for global trade and technical exchange of materials.

Conclusion

With its high measurement precision, broad applicability, easy operation, safety performance, and compliance with international standards, the Limiting Oxygen Index Tester has become a key instrument in the field of flame-retardancy testing.

With continuous technological advancement, LOI testing equipment will continue to evolve, providing stronger support for material science research and industrial safety development.

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.