Limiting Oxygen Index (LOI) Apparatus
The Limiting Oxygen Index (LOI) Apparatus measures the minimum oxygen concentration required to sustain combustion of a material under specified test conditions. The test specimen is placed vertically in a combustion tube through which a controlled mixture of oxygen and nitrogen flows. The oxygen concentration is adjusted to determine the limiting oxygen index, expressed as a percentage by volume.
The instrument features digital display and sensor-based oxygen measurement, allowing test results to be read directly without manual calculation. It is suitable for evaluating the combustion behavior of plastics, rubber, foam, and other compatible materials. The results support flame-retardant material development, product quality control, and comparative evaluation of material flammability.
Application
(1) Plastics and polymer materials.
(2) Rubber and elastomeric materials.
(3) Foam materials and cellular plastics.
(4) Electrical cable insulation and polymer components.
(5) Flame-retardant material research and development.
(6) Quality control and comparative combustion testing in laboratories and manufacturing facilities.
Standards
ISO 4589-2:2017 — Plastics — Determination of burning behaviour by oxygen index — Part 2: Ambient-temperature test
ASTM D2863-23e1 — Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index)
GB/T 2406.2-2009 — Plastics — Determination of burning behaviour by oxygen index — Part 2: Ambient-temperature test
Parameters
| Parameter | Specification |
|---|---|
| Inner diameter of combustion tube | 100 mm |
| Height of combustion tube | 450 mm |
| Flowmeter accuracy class | Class 2.5 |
| Pressure gauge accuracy class | Class 2.5 |
| Oxygen supply | Industrial oxygen conforming to GB/T 3863-2025 |
| Nitrogen supply | Industrial nitrogen conforming to GB/T 3864-2025 |
| Operating temperature | 10–35°C |
| Relative humidity | 45–75% RH |
| Gas inlet pressure | 0.2–0.3 MPa |
| Working pressure | 0.05–0.15 MPa |
| Applicable specimen types | Self-supporting and non-self-supporting materials |
| Display | Digital |
Features
(1) Measures the limiting oxygen concentration required to sustain combustion under specified conditions.
(2) Uses sensor-based oxygen measurement and digital display for convenient result reading.
(3) Supports oxygen index testing of self-supporting and non-self-supporting specimens, subject to the applicable test method.
(4) Uses a vertical combustion tube and an oxygen-nitrogen gas mixture for controlled testing.
(5) Provides direct digital readings, reducing the need for manual calculation.
(6) Suitable for flame-retardant material research, incoming material inspection, and routine quality control.
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