Information on the most widely used ASTM standards within the materials testing industry
Model: YZS-100A, YZS-100B
Oxygen Index Apparatus/LOI tester (Limitation Oxygen Index tester) is widely used to measure burning performance of plastics, rubber, fiber, foam, softening sheet, film etc.,
The Oxygen Index is the most economical and precise quality control test of combustible materials. Its ease of use together with high levels of precision has made this technique a primary characterising and quality control tool to the plastic and electric cable industries and it has been specified by several military and transport groups. The technique measures the minimum percentage of oxygen in the test atmosphere that is required to marginally support combustion.
ISO 4589-2 " Plastics -- Determination of burning behaviour by oxygen index -- Part 2: Ambient-temperature test”
ASTM D2863 " Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index) “
General introduction
An oxygen index tester — also called a limiting oxygen index (LOI) tester or oxygen index apparatus — measures the minimum concentration of oxygen, expressed as a volume percentage, that will just support flaming combustion of a material in a controlled oxygen/nitrogen atmosphere.
It is one of the most economical and precise quality-control tests available for combustible materials, and it is written into ISO 4589-2, ASTM D2863, NES 714, EN 45545-2 and GB/T 2406.2.

The oxygen index tester, also known as the limiting oxygen index (LOI) test machine, is a precision flammability testing instrument designed to measure the minimum oxygen concentration required to sustain combustion of polymeric materials under controlled laboratory conditions. UnitedTest (Beijing United Test Co., Ltd.), as a professional manufacturer of flammability testing equipment, produces the YZS-100 series oxygen index apparatus that fully complies with international standards including ISO 4589-2, ASTM D2863, NES 714, and EN 45545-2.
As one of the most economical and precise quality control methods for combustible materials, the oxygen index test has become a primary characterization tool for the plastics, cable, automotive, aerospace, and construction industries. The technique measures the minimum volume percentage of oxygen in a nitrogen-oxygen mixture that will marginally support candle-like combustion of a vertically oriented specimen.
UnitedTest offers both ambient temperature oxygen index testers (YZS-100A/B series) and high temperature oxygen index testers for elevated temperature testing up to 400°C per ISO 4589-3
Main Features
Precision & Accuracy
Imported high-accuracy oxygen sensor delivers direct digital oxygen concentration display, eliminating personal reading error
0.1% oxygen concentration resolution for precise measurement
Digital reading of limiting oxygen index value directly on the control panel
2.5 class accuracy flow meters and pressure gauges
Structural Design
- Reasonable structure with separate main control box and burning tube assembly for easy operation
- Front panel features ash black frosted plastic finish with 304 stainless steel decorative trim
- Robust frame construction ensures long-term stability
- Compact footprint: 590 × 480 × 560 mm (frame dimensions)
| Feature | YZS-100A | YZS-100B |
| Pressure display | Dial gauge | Digital meter |
| Oxygen reading | Digital display | Digital display |
| Burning tube diameter | 100 mm standard (75 mm optional) | 100 mm standard (75 mm optional) |
| Burning tube height | 450 mm | 450 mm |
ISO 4589-2 " Plastics -- Determination of burning behaviour by oxygen index -- Part 2: Ambient-temperature test”
ASTM D2863 " Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index) “
- NES 714: Naval engineering standard for material flammability assessment
- EN 45545-2: Railway application fire safety standard for materials and components
- ISO 4589-3: Elevated-temperature oxygen index test (available on high-temperature models)
The UnitedTest oxygen index tester serves a wide range of industries for material flammability assessment, quality control, and regulatory compliance:
Plastics industry: Raw material formulation, compound development, quality control
Wire & cable industry: Insulation material testing, cable jacket evaluation
Electrical industry: Printed circuit boards, connector materials, enclosure plastics
Aerospace industry: Interior material qualification, component fire safety
Automotive industry: Interior components, under-hood materials, wire harnesses
Construction industry: Building insulation, decorative materials, sealing products
Railway industry: EN 45545-2 compliance testing for train interior materials
Research institutions: University laboratories, material research centers, certification bodies
Test Principle
A small test specimen is supported vertically in a mixture of oxygen and nitrogen flowing upwards through a transparent quartz chimney. The upper end of the specimen is ignited, and the subsequent burning behavior is observed. By testing a series of specimens at different oxygen concentrations using the bracketing method, the minimum oxygen concentration (limiting oxygen index) that just supports combustion is determined.
Complete Test Procedure
Specimen preparation: Cut specimens to standard dimensions (80–150 mm × 10 mm, thickness 4 mm or 10 mm) and condition according to standard requirements.
System setup: Mount the specimen vertically on the specimen holder inside the glass chimney. Connect oxygen and nitrogen gas supplies with input pressure regulated to 0.2–0.3 MPa.
Gas flow adjustment: Set the oxygen-nitrogen ratio to the desired starting concentration, maintaining total gas flow at the specified velocity.
Ignition: Ignite the top of the specimen using the propane igniter, ensuring proper flame application.
Observation: Monitor burning duration and burning length to determine if the oxygen concentration is above or below the limiting value.
Concentration adjustment: Systematically adjust the oxygen concentration up or down using the bracketing method until the critical LOI value is identified.
Result calculation: Calculate and record the limiting oxygen index value as a volume percentage.
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Main technical specification
| Model | YZS-100A | YZS-100B |
| Pressure display | Dial gauge | Digital meter |
| Limitation Oxygen index value | Digital reading directly | |
| Burning tube inner diameter | 100mm 75mm (optional) | |
| Burning tube height | 450mm | |
| Flow meter accuracy | 2.5 calss | |
| Pressure meter accuracy | 2.5 calss | |
| Gas source | Oxygen, Nitrogen | |
| Input pressure | 0.2~0.3Mpa | |
| Working pressure | 0.05~ 0.15Mpa | |
| Oxygen concentration resolution | 0.1% | |
| Sample type | Self supporting, or non-self supporting | |
| Weight | Frame: 52Kg Gross weight: 65Kg | |
| Dimension | Frame: 590*480*560mm Package: 690*580*790mm | |
| Power | 220V, 50Hz/110V, 60HZ, single phase | |
Main Accessories
| Item | Quantity |
| Frame | 1 set |
| Burning tube | 1 set |
| Igniter | 1 pc |
| Sample clip | 2 pcs |
| Tube clip | 1 pc |
| Stopwatch | 1 pc |
| Strengthen plastic tube | 1 pc |
| Glass ball | 2 bags |
| Documents (Manual, packing list, certificate) | |
self supporting material gripper
sample supporting fixture
non-self supporting material gripper
Standard
ISO 4589-2 Plastics — Determination of burning behaviour by oxygen index — Part 2: Ambient-temperature test
ISO 4589-2 defines how to measure the oxygen index (OI) — the minimum volume fraction of oxygen, in admixture with nitrogen, that will just support flaming combustion of a small vertical test specimen under specified conditions, at ambient temperature (23 °C ± 2 °C). Results are expressed as a percentage, e.g. OI = 29,5 %.
It covers self‑supporting vertical bars/sheets up to 10,5 mm thick (solid, laminated or cellular materials with apparent density ≥ 100 kg/m³, and possibly some below that), plus a method for flexible sheet/film tested while vertically supported. It also gives a short procedure to check compliance with a specified minimum OI. Note: it may not work satisfactorily for materials with high thermal shrinkage, e.g. highly oriented thin film.
ISO 4589-3:2017 Plastics — Determination of burning behaviour by oxygen index Part 3: Elevated-temperature test
ISO 4589-3 specifies methods for determining the minimum volume fraction of oxygen, in a mixture with nitrogen, that will support combustion of small vertical test specimens under specified test conditions over a range of temperatures between 25 °C and 150 °C. The range of temperatures is typically between 40 °C and 150 °C. The results are defined as temperature index values at the test temperature, which is typical of the practical temperature that a plastic material can experience in an overheated service situation.
Methods are provided for testing materials that are self-supporting at the test temperature in the form of vertical bars or sheet up to 10,5 mm thick. However, they are not applicable to form V which requires a supporting frame as defined in ISO 4589‑2:2017, Table 2. These methods are suitable for solid, laminated or cellular materials characterized by an apparent density 100 kg/m3 or higher. The methods are also applicable to some cellular materials having an apparent density of less than 100 kg/m3. A method is provided for testing flexible sheet or film materials while supported vertically.
ASTM D2863: Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index)
Test Scope:
ASTM D2863 is a method to determine the minimum concentration of oxygen in an oxygen/nitrogen mixture that will support a flaming burn in a plastic specimen. There is no correlation to real end use conditions.
Frequently Asked Questions (FAQ)
A: The primary difference is the pressure display method. YZS-100A uses an analog dial gauge for pressure indication, while YZS-100B features a digital pressure meter. Both models provide the same oxygen concentration measurement accuracy and test performance.
A: The oxygen index tester can evaluate virtually all combustible materials including plastics, rubber, fiber, foam, softening sheets, films, laminates, and printed circuit boards. Both self-supporting rigid materials and non-self-supporting flexible materials can be accommodated with appropriate specimen holders.
A: A complete test series requires approximately 20 specimens to accurately determine the limiting oxygen index using the bracketing method. For routine quality control at a specified oxygen concentration, a reduced test series of 8 specimens is sufficient.
A: Standard specimens measure 80–150 mm in length × 10 mm in width, with typical thicknesses of 4 mm or 10 mm. Different thicknesses can be accommodated depending on material type and specific standard requirements.
A: The standard YZS-100 series operates at ambient temperature per ISO 4589-2 and ASTM D2863. UnitedTest also offers high temperature oxygen index tester models that can test at temperatures up to 400°C in compliance with ISO 4589-3. Contact our engineering team for elevated temperature configuration options.
A: The test works by flowing a controlled mixture of oxygen and nitrogen upward through a glass chimney containing a vertically mounted specimen. The specimen is ignited at the top, and the minimum oxygen concentration that just sustains flaming combustion is determined by systematically adjusting the gas mixture ratio.
A: UnitedTest oxygen index testers feature imported high-precision oxygen sensors with 0.1% resolution. The flow meters and pressure regulators achieve 2.5 class accuracy, ensuring reliable and repeatable LOI measurements.
Beijing United Test Co., Ltd. (UnitedTest) is a specialized manufacturer of advanced flammability testing equipment with years of experience in material fire testing technology. Our YZS-100 series oxygen index apparatus represents the industry standard for reliable, accurate, and cost-effective LOI testing.
Full standard compliance: All models meet ISO 4589-2, ASTM D2863, NES 714, EN 45545-2, and other major standards
Precision manufacturing: Strict quality control with ISO 9001 certified production processes
Competitive pricing: In-house manufacturing delivers exceptional value without compromising quality
Technical support: Professional installation, calibration, training, and after-sales service
Custom solutions: High-temperature upgrades, automated configurations, and custom fixtures available
YZS-100A: Economy oxygen index tester with dial gauge pressure display
YZS-100B: Digital oxygen index tester with full digital instrumentation
HT Series: High temperature oxygen index testers up to 400°C (ISO 4589-3 compliant)
Automated LOI systems: Fully computer-controlled systems for advanced research applications
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