ISO 4589-3 elevated Tempreature oxygen index test | UnitedTest High Temperature LOI tester

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Flexural & Bend tests evaluate material resistance to bending forces, measuring strength, stiffness and ductility for quality assurance. UnitedTest provides flexural testing machines (3-point/4-point bend) compliant with ASTM/ISO standards, offering tailored solutions for composites, plastics, metals and construction materials.

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ISO 4589-3 Elevated Temperature Oxygen Index Tester | Plastic Flammability Test | UnitedTest

ISO 4589-3 specifies elevated-temperature oxygen index testing for plastics, measuring Temperature Index (TI) and Flammability Temperature (FT) to evaluate hot-condition plastic flammability. UnitedTest manufactures fully compliant ISO 4589-3 flammability test machines for high-temperature material fire safety analysis.

ISO 4589-3 is the specialized international standard for determining the burning behaviour and flammability performance of plastics via oxygen index testing under elevated temperature conditions, serving as the high-temperature counterpart to the ambient-temperature ISO 4589-2 test standard. This advanced testing method adapts the classic oxygen index principle to heated environments, accurately evaluating how flammable plastic materials become when exposed to sustained high-temperature working conditions, which simulates real-world overheating and thermal exposure scenarios for polymer products. It takes the classic oxygen-index (OI) test and runs it hot, to answer "how flammable is this plastic when it is already hot?"

The standard defines two core testing parameters for comprehensive high-temperature flammability assessment: Temperature Index (TI) refers to the minimum oxygen volume fraction required to sustain stable flaming combustion of vertical plastic specimens at elevated test temperatures. Flammability Temperature (FT), specified in the normative Annex A, represents the critical temperature at which a plastic specimen achieves sustained burning under normal atmospheric air containing 20.9% oxygen concentration. Covering a typical test temperature range of 40 °C to 150 °C, the test delivers reliable data for evaluating thermal flammability degradation of various plastic, laminated, and cellular polymer materials.

Widely applied in fire safety certification, polymer material R&D, electrical plastic component inspection, automotive plastic testing and industrial material quality control, ISO 4589-3 effectively compensates for the limitations of ambient-temperature flammability tests. UnitedTest designs and manufactures high-precision ISO 4589-3 elevated-temperature oxygen index testers, supporting accurate TI and FT value measurement, fully compliant with standard specifications to deliver stable and repeatable high-temperature flammability test results for laboratory and industrial use.

Test principle

A small vertical specimen is placed inside a heated transparent chimney, through which upward‑flowing oxygen‑nitrogen gas mixture passes. The top of the specimen is ignited. Operators observe whether combustion continues beyond specified burning‑time or burnt‑length thresholds. By repeating tests at varied oxygen concentrations, the minimum oxygen fraction (Temperature Index, TI) that maintains sustained flaming combustion is found.

For FT measurement (Annex A), only air (20.9 % O₂) flows; test temperature is adjusted until the specimen just satisfies the burning criteria, giving the flammability temperature (FT, below 400 °C).

Test methods

Temperature Index (TI) measurement

Measure minimum oxygen volume fraction for sustained combustion at target elevated temperature (25–150 °C, typical 40–150 °C).

Uses Dixon’s up‑and‑down method for sequential oxygen‑level adjustment and calculation. A short procedure can verify whether TI exceeds a specified minimum threshold.

Flammability Temperature FT measurement

Test under air (20.9 % oxygen). Adjust chamber temperature to find the lowest temperature that just supports specimen flaming combustion.

Requires at least three replicate determinations to calculate average FT.

FT testing is limited to temperatures below 400 °C and is invalid for materials whose room‑temperature oxygen index is less than 20.9 %.

Test Specimen Information

Applicable materials: Self‑supporting bars/sheets up to 10.5 mm thickness; solid, laminated, cellular plastics with apparent density ≥100 kg/m³; some low‑density cellular materials; supported flexible films/sheets. Form V specimen is excluded.
Dimensions: Follow specimen dimension rules of ISO 4589-2.
Sample quantity: FT test needs minimum 10 specimens; TI test requires multiple specimens for Dixon up‑and‑down series.
Support rule: Specimens losing self‑support at test temperature must be mechanically supported with nichrome wire fixtures.

Test equipment required for ISO 4589-3 elevated Tempreature oxygen index test

Recommend UntiedTest YZS series Oxygen Index Tester/Limiting Oxygen Index (LOI) Test Machine, consist of below:

Heated test chimney	Two concentric heat-resistant glass tubes between an insulating top plate and a base. Inner tube: 450–500 mm high, 75–100 mm bore; annular gap 5–10 mm. Base contains a gas-distribution bed (3–5 mm glass beads, 80–100 mm deep).
Chimney heating element + gas preheater	nichrome winding up to ~1 000 W on the outer tube (graded pitch for even temperature) plus a ceramic preheater up to ~1 000 W with independent control. A preheater is not needed if the target is ≤ 150 °C.
Outlet restrictor cap	Converging to a 40 mm outlet ≥ 10 mm above the chimney top, to give ≥ 90 mm/s exhaust velocity.
Specimen holder & transfer tool	Specimen holder as specified in ISO 4589‑2. Transfer tool inserts pre‑heated specimens into the hot chimney without excessive temperature drop. Non‑self‑supporting specimens use 0.55 mm nickel‑chromium support wires and 0.20 mm copper tie wires.
Gas supply & control devices	Oxygen and nitrogen sources; gas‑flow sensing interlock to protect heaters from dry over‑heating. Gas velocity inside chimney shall be 40 mm/s ±0.8 mm/s (at 23 °C).
Oxygen analyser	Measures real‑time oxygen volume fraction of mixed gas.
Thermocouples	Monitor gas temperature close to specimen position with minimal flow turbulence disturbance.

Key Test Parameters

Test temperature range for TI	25 °C‑150 °C (typical operating range: 40 °C‑150 °C)
Gas flow velocity	40 mm/s ±0.8 mm/s (referenced to 23 °C)
Specimen pre‑heat time before ignition	240 s ±10 s
Chimney purge time before each ignition	≥30 s
Temperature tolerance ≤125 °C	±3 °C
Temperature tolerance >125 °C	±5 °C
Ignition flame application duration	15 s ±1 s
FT maximum allowed temperature	<400 °C
Typical oxygen‑fraction step for TI test	0.2 % volume fraction

Test procedure of ISO 4589-3 elevated Tempreature oxygen index test

Set‑up apparatus: Stabilise chimney temperature; adjust gas flow to 40 mm/s ±0.8 mm/s. Position thermocouple near specimen location.
Mount specimen in holder; insert specimen assembly into heated chimney by transfer tool.
Pre‑heat specimen for 240 s ±10 s; purge chimney with target gas mixture for ≥30 s.
Ignite specimen top with standard propane flame (15 s ±1 s ignition application).
Record burning duration and burnt length; judge pass/fail against standard criteria.
Adjust oxygen fraction (TI test) or test temperature (FT Annex A test) following up‑and‑down rules. Repeat tests.
Compute TI (Dixon method) or average FT value; verify step‑size validity.
Document all observations and produce complete test report.

Industry Application Fields

ISO 4589‑3 serves plastic R&D, quality control and material‑selection scenarios for products operating under elevated‑temperature service conditions:

- Electrical & electronic plastics (enclosure, insulating parts subject to heating)

- Automotive interior and engine‑compartment polymer components

- Aerospace plastic parts

- Industrial equipment plastic components exposed to heat

- Building‑construction polymer materials

- Research and development for high‑temperature‑resistant flame‑retardant plastic formulations

Related Test Standard:

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)
GB/T 2406.2	Plastics.Determination of burning behaviour by oxygen index.Part 2:Ambient-temperature test
GB/T 5454	Textiles--Burning behaviour--Oxygen index method
ISO 4589-3	Plastics - Determination of burning behaviour by oxygen index - Part 3: Elevated-temperature test
GB/T 2406.3	Plastics—Determination of burning behaviour by oxygen index—Part 3: Elevated-temperature test
IEC 61144	Test method for the determination of oxygen index of insulating liquids
JIS K 7201	Plastics -- Determination of burning behaviour by oxygen index -- Part 2: Ambient-temperature test
GB/T 16581	Test method for the determination of oxygen index of insulating liquids
ISO 3582	Horizontal flammability test for flexible cellular polymers

Why ISO 4589-3 Important for Polymeric Materials

1. Ambient OI is misleading for hot service. Oxygen index drops steeply with temperature — a material with a comfortable OI of 30 % at 23 °C can drop below 21 % (i.e. become flammable in normal air) at only 100–150 °C. TI at a realistic service temperature is the number that actually predicts whether an overheated part will sustain a flame.

2. FT gives a single, intuitive safety threshold — "this polymer will not sustain flaming in ordinary air below ~270 °C". That is directly usable for setting maximum service temperature, creep/overload limits, and thermal-protection set-points.

3. It separates materials that look identical at room temperature. Two FR grades with the same ambient OI can diverge widely at 100 °C because different FR systems (halogenated, phosphorus, mineral filler, intumescent) respond differently to pre-heating. TI is therefore a powerful formulation-selection and QC discriminator.

4. It feeds fire-risk assessment and compliance as one controlled, reproducible input — small specimen, cheap, quantitative, statistically treated, with defined temperature control, which purely rating-based tests (UL 94) do not provide.

5. It is honest about its own limits: the standard insists results are comparative material properties, not fire-hazard verdicts, and (unusually) currently carries no precision statement — so FT/TI values should be compared with a margin rather than treated as exact numbers.

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High-temperature limit oxygen index tester refers to the volume fraction concentration of oxygen that can support the combustion of materials in a mixture of oxygen and nitrogen gas, and is an index that characterizes the combustion behavior of materials.

Oxygen Index Apparatus/LOI tester (Limitation Oxygen Index tester) is widely used to measure burning performance of plastics, rubber, fiber, foam,,film etc., The technique measures the minimum percentage of oxygen in the test atmosphere that is required to marginally support combustion.

ISO 4589‑2 LOI test apparatus is widely used for flammability testing of plastics, polymer compounds, rubber, rigid & flexible foam materials, cable‑insulation materials, composite laminates, thin packaging films, automotive‑interior plastics, building‑decorative polymer materials, E&E component plastics.

High Temperature Oxygen Index Tester for ISO 4589-3 — Temperature Index (TI) and Flammability Temperature (FT)

ISO 4589-3:2017 — Plastics — Determination of burning behaviour by oxygen index — Part 3: Elevated-temperature test — answers a question that room-temperature testing cannot: how flammable is this plastic once it is already hot? Beijing United Test Co., Ltd. (UnitedTest) manufactures the HTYZS-100E high temperature oxygen index test apparatus, a heated-chimney system engineered for ISO 4589-3 as well as ISO 4589-2, ASTM D2863, GB/T 2406.3, NES 714 and EN 45545-2.

Q1: What is ISO 4589‑3 test, and what do TI and FT stand for?

A: ISO 4589‑3 is the international standard for elevated‑temperature oxygen‑index flammability test for plastics.

TI (Temperature Index): Minimum oxygen volume fraction (%) to sustain flaming combustion at target elevated test temperature (25–150 °C, typical 40‑150 °C).

FT (Flammability Temperature, Annex A normative): The lowest temperature at which specimen maintains flaming combustion in normal air (20.9 % oxygen), max test limit <400 °C.

Q2: Why is ISO 4589‑3 test important? Why cannot I just use ISO 4589‑2 ambient oxygen‑index results?

A: ISO 4589‑2 only measures flammability at room temperature (23 °C). Many plastic parts work under over‑heated service conditions (automotive engine compartments, electrical enclosures). As temperature rises, plastics require far less oxygen to keep burning. Room‑temperature OI values often overestimate real‑world flame resistance under heat. ISO 4589‑3 simulates actual high‑temperature service environment and outputs TI/FT data to evaluate flame‑retardant performance under heating conditions, supporting material selection, R&D and component specification verification.

Q3: What is the core difference between ISO 4589‑2 and ISO 4589‑3?

Item	ISO 4589‑2	ISO 4589‑3
Test temperature	Fixed ambient 23 °C ±2 °C	Adjustable elevated temperature:25‑150 °C; FT test up to <400 °CISO
Key result	Ambient Oxygen Index (OI)	Temperature Index (TI), Flammability Temperature (FT)
Hardware	Standard oxygen‑index chimney	Heated chimney + gas pre‑heater, specimen transfer tool, high‑temperature thermocouples
Annex A	N/A	Normative FT measurement in air

Q4: What materials are suitable / NOT suitable for ISO 4589‑3 testing?

A:✅ Suitable: self‑supporting bars / sheets up to 10.5 mm thick; solid, laminated plastics; cellular foams ≥100 kg/m³; some low‑density foams; supported flexible films.

❌ Not suitable: Form V specimen; highly‑oriented thin films with severe thermal shrinkage; materials whose room‑temperature OI <20.9 % (cannot run FT test). If specimen softens and loses self‑support at test temperature, nichrome wire fixture is required for external support.

Q5: What are critical test parameters I need pay close attention to?

A: Gas velocity inside heated chimney must be 40 mm/s ±0.8 mm/s (referenced to 23 °C)

Specimen pre‑heat time before ignition: 240 s ±10 s for thermal equilibrium.

Temperature tolerance: ±3 °C ≤125 °C; ±5 °C above 125 °C.

Pre‑purge chimney ≥30 s before each ignition; gas flow must keep stable during burning observation.

FT test requires minimum three replicate measurements, final FT is average rounded to nearest 1 °C.

Q6: Can ISO 4589‑3 TI / FT results directly predict real‑fire hazard of plastic products?

A: No. ISO standard explicitly states TI and FT are only bench‑scale laboratory results under strictly controlled conditions. Real‑world fire involves large heat flux, ventilation, product geometry and assembly factors. TI/FT can only serve as one input for comprehensive fire‑risk assessment instead of standalone hazard judgment.

Q7: Why need specimen transfer tool for ISO 4589‑3 test?

A: The chimney is pre‑heated to high temperature. Direct manual placement will cool down the hot chamber and specimen. The transfer tool inserts pre‑mounted specimen holder into heated chimney with minimal temperature disturbance to guarantee test reproducibility.

Q8. What is the difference between ISO 4589-1, -2, -3 and -4?

A: Part 1 (ISO 4589-1) — general requirements and guidance for the whole series.

Part 2 (ISO 4589-2) — the basic test at ambient temperature (23 °C) → oxygen index, OI.

Part 3 (ISO 4589-3) — the same determination at elevated temperature, typically 25–150 °C → temperature index (TI); plus Annex A for flammability temperature (FT) up to 400 °C.

Part 4 (ISO 4589-4:2021) — high gas velocity test at ambient temperature → HOI, for sheet up to 2 mm thick.

Q9. What is flammability temperature (FT) in plain terms?

A: FT is the temperature at which the material's oxygen index drops to exactly 20.9 %, the oxygen content of normal air. Below FT the material cannot sustain flaming in ordinary air; at or above FT it can. It is the single most intuitive "how hot is too hot" number for a polymer.

Q10: Why can't I just use the room-temperature OI result?

A: Because pre-heating the polymer removes most of the energy needed to bring it to pyrolysis temperature, so less oxygen is needed to keep it burning. A material rated safe at OI 30 % at 23 °C may fall below 21 % at 100–150 °C and therefore burn in air when overheated. Ambient OI systematically over-states the safety margin of any part that runs hot.

Q11. What temperature range and tolerances does ISO 4589-3 require?

A: TI testing: 25–150 °C, typically 40–150 °C, held to ± 3 °C up to and including 125 °C and ± 5 °C above that. FT testing: permitted up to 400 °C, with the temperature gradient between the specimen top and 50 mm below it kept below 5 °C. FT is established to within a 5 °C increment.

Q12. What must appear in the ISO 4589-3 test report?

A: Reference to ISO 4589-3; the disclaimer statement; full material identification including type, density, history and orientation relative to anisotropy; specimen form and dimensions; method of support; ignition procedure (A or B) and igniter used; the TI or FT value; the test temperature; estimated standard deviation and oxygen step size if other than 0.2 %; any ancillary behaviour such as charring, dripping, severe shrinkage, erratic burning or afterglow; and any deviations from the standard.

Q13: Why choose ISO 4589‑3 Elevated‑Temperature Oxygen Index Tester from UnitedTest?

A: UnitedTest manufactures professional ISO 4589‑3 elevated‑temperature oxygen index tester for plastics, measuring Temperature Index (TI) and Flammability Temperature (FT) to evaluate plastic flammability under high‑temperature service conditions for automotive, electrical, aerospace and polymer R&D labs.

UnitedTest is a professional manufacturer of ISO 4589‑3 high‑temperature oxygen‑index test machine, fully compliant with ISO 4589‑3:2017 international standard for plastics burning‑behaviour measurement at elevated temperatures.

Our ISO 4589‑3 test equipment determines Temperature Index (TI) and Flammability Temperature (FT) of plastic specimens under controlled heating environment. It simulates real‑world over‑heated working conditions for polymer materials, filling the gap of ambient‑temperature oxygen‑index test (ISO 4589‑2).

Key test capabilities of UnitedTest ISO 4589‑3 tester:

Adjustable test temperature 25 °C‑150 °C for TI measurement; support FT test up to below 400 °C (Annex A method)
Precision‑controlled heated glass chimney plus gas pre‑heating system; temperature tolerance complies with ISO 4589‑3 requirement
Standard specimen transfer tool for hot‑chamber specimen loading to avoid temperature drop
High‑precision gas flow control: 40 mm/s ±0.8 mm/s gas velocity
Built‑in oxygen analyser, timing system, propane flame igniter and fume extraction unit
Supports self‑supporting bars, sheets, cellular plastics and supported flexible films
Implements Dixon up‑and‑down calculation logic for TI computation; supports Annex A FT flammability‑temperature test workflow

This ISO 4589‑3 flammability tester is widely used in:

✅ Automotive polymer component labs (engine‑compartment plastics)

✅ Electrical & electronic plastic enclosure and insulating material quality control

✅ Aerospace plastic material qualification

✅ Flame‑retardant polymer R&D for new‑formula development

✅ Third‑party testing laboratories, university material research institutes

Compared with conventional room‑temperature oxygen‑index instruments, UnitedTest ISO 4589‑3 machine reveals how flame resistance degrades when plastics are exposed to heat. It delivers reliable TI and FT benchmark data for material comparison, component specification verification and fire‑risk assessment input.

UnitedTest provides complete after‑sales service including installation, operation training, calibration guidance and technical support for ISO 4589‑3 standard test procedures. Contact us to get quotation for your elevated‑temperature oxygen‑index testing solution.

We offer customization to meet your specific needs. Our expert team will collaborate with you to develop the perfect product for you

ISO 4589-3 High Temperature Oxygen Index Test Temperature Index (TI) and Flammability Temperature (FT)