ISO 4589-2 Plastics Oxygen Index Test | LOI Test Apparatus

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ISO 4589-2 Oxygen Index Tester for Plastics | UnitedTest

UnitedTest manufactures ISO 4589-2 oxygen index testing machine to determine ambient-temperature oxygen index (OI) of plastics, evaluating flammability and burning behaviour of solid, laminated, cellular and flexible plastic specimens.

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.

UnitedTest supplies reliable oxygen index testers fully complying with ISO 4589-2 standard for plastic flammability testing in material laboratories.

Test principle

A small specimen is held vertically in a transparent chimney through which an oxygen/nitrogen mixture flows upwards. The upper end is ignited, and the burning behaviour is compared with limits on burning time (180 s) and burnt length (50 mm / 80 mm depending on form). By testing a series of specimens at successively different oxygen volume fractions using the "up‑and‑down" (Dixon) staircase method, the OI is estimated statistically.

Alternative: for comparison with a specified minimum OI, three specimens are tested at that oxygen level; at least two must give an "O" (self‑extinguishing within limits) response.

ISO 4589-2 Plastics burning oxygen index test - LOI Test

Test Specimen Information

Six specimen forms (I‑VI) cover rigid bars, sheets, foams, flexible sheets and thin films:

Specimen type	Typical use	Key dimensions
I	Moulding rigid plastics	Length 80‑150 mm; width 10 ± 0.5 mm; thickness 4 ± 0.25 mm
II	Cellular foam materials	Length 80‑150 mm; width 10 ± 0.5 mm; thickness 10 ± 0.5 mm
III	As‑received sheet	Length 80‑150 mm; width 10 ± 0.5 mm; thickness ≤ 10.5 mm
IV	Electrical‑grade rigid plastics	Length 70‑150 mm; width 6.5 ± 0.5 mm; thickness 3 ± 0.25 mm
V	Flexible sheet / film (needs frame support)	Length 140‑150 mm; width 52 ± 0.5 mm; thickness ≤ 10.5 mm
VI	Very thin film (rolled‑film sample)	Original film thickness 0.02‑0.10 mm; rolled specimen length 140‑200 mm

Sampling: Minimum 15 specimens are generally needed; unknown or erratically‑burning materials need 15‑30 specimens.

Test equipment required for ISO 4589-2 Plastics burning oxygen index test - LOI Test

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

Test chimney	Heat‑resistant glass tube, vertical; recommended 450–500 mm high, 75–100 mm internal diameter; top restricted by a cap giving exhaust velocity ≥ 90 mm/s (e.g. converging to a 40 mm outlet ≥ 10 mm above the top); base with diffuser + mixing chamber (metal honeycomb foil or glass beads); debris screen below the holder; levelling device; dark background aids observation
Specimen holder	Holds specimen in the chimney centre. Self‑supporting: small clamp, ≥ 15 mm away from the nearest possible burning point. Film/sheet (form V): frame gripping both vertical edges, with reference marks 20 mm and 100 mm below the frame top
Gas supplies	Pressurized O₂ and/or N₂ of ≥ 98 % (m/m) purity, and/or clean air (20,9 % O₂). Moisture of the mixture entering the chimney < 0,1 % (m/m) unless results are shown insensitive → drying device or moisture monitoring required
Gas control	Resolution 0,1 % O₂; adjustability ± 0,2 % of the mixture; gases thoroughly premixed so the O₂ variation below specimen level is < 0,2 %. Four acceptable systems: needle valves + O₂ analyser + flow meter; calibrated orifices + pressure regulators/gauges; needle valves + calibrated flow meters; or mass‑flow controllers
Oxygen analyser	Resolution 0,1 %, accuracy ± 0,1 % (paramagnetic types typical)
Flame igniter	Tube with 2 mm ± 1 mm outlet; fuel propane without premixed air, purity ≥ 98 %; total flame height 16 mm ± 4 mm with the tube vertical in the chimney (flame‑height gauge recommended)
Timer	Range to 5 min, accuracy ± 0,5 s
Fume extraction	Removes fumes/soot without disturbing chimney flow or temperature
Rolled‑film tool	Stainless‑steel rod, 2 mm diameter, with a slit at one end

Key Test Parameters

1. Gas velocity inside chimney: 40 ± 2 mm/s (at 23 °C). Purge chimney with test gas mixture for minimum 30 s before igniting each specimen.

2. Ignition flame height: 16 ± 4 mm; propane fuel purity ≥ 98 %. Maximum ignition application time 30 s, inspected every 5 s intervals to judge successful ignition.

3. Burn‑failure criteria: If burning duration exceeds 180 seconds OR burning front travels past specified reference mark → “X” response (burning continues). If both limits are not exceeded → “O” response (self‑extinguished).

4. Standard oxygen‑concentration step size d = 0.2 % volume fraction for up‑and‑down statistical test sequence.

Test procedure of ISO 4589-2 Plastics burning oxygen index test - LOI Test

1. Preparation: Calibrate apparatus, clean glass chimney. Condition specimens. Select initial oxygen concentration according to preliminary burning observation in air. Ensure chimney vertical; mount specimen centrally inside chimney meeting position‑offset requirements (top ≥ 100 mm below chimney outlet; specimen bottom ≥ 100 mm above gas diffuser).

2. Set gas flow to achieve gas velocity 40 ± 2 mm/s, stabilise, purge chimney ≥ 30 s before ignition. Record oxygen‑analyser reading.

3. Ignite specimen following Procedure A or B; start timing upon successful ignition.

4. Evaluate burning response “O” or “X” according to burn‑time and burn‑length criteria; note dripping, charring, glowing or erratic combustion. Remove burnt specimen and clean chimney components.

5. Preliminary search phase: Adjust oxygen concentration step‑wise. Locate a pair of oxygen levels differing ≤ 1.0 % giving one “O” and one “X”. Record the “O”‑response oxygen value as preliminary starting concentration.

6. Main up‑and‑down measurement phase: Use step size d = 0.2 %. Collect NL series (initial consistent responses) plus five further specimens to build total NT=NL+5 dataset.

7. Compute estimated standard deviation using final six test points. Verify step‑size validity against statistical condition. Adjust step size if condition fails and repeat testing.

8. OI calculation: Round final OI result for reporting.

Industry Application Fields

Plastics & polymer material R&D and incoming‑goods quality‑control.

Fire‑retardant formulation development: screening and comparing different flame‑retardant additive formulations for polymers.

Electrical & electronic plastic components, building interior polymer materials, automotive interior plastics, composite laminates, foam materials, flexible packaging films.

Material‑spec compliance verification for procurement specifications, factory quality‑control screening.

Laboratory inter‑laboratory comparison of flammability performance of polymer grades.

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
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 4589‑2 OI Test is Important for Polymeric Materials

Sensitive comparative screening: OI gives quantitative numeric value for relative flammability. Higher OI means greater resistance to sustained flaming combustion in controlled oxygen‑rich/lean environment. It is widely used to compare base‑resin grades and the efficiency of different flame‑retardant additive systems during polymer formulation work.

Quality‑control tool: Manufacturers use OI for batch‑to‑batch consistency monitoring of fire‑retarded plastics, to verify whether flame‑retardant content remains within specification in mass‑production parts.

Bench‑level laboratory‑data input: Provides repeatable, reproducible small‑scale data as one element of complete fire‑risk assessment for material‑application engineering.

Specification compliance: Many material procurement and component‑product specifications reference ISO 4589‑2 minimum‑OI thresholds for acceptance criteria.

Pre‑selection for further expensive large‑scale fire tests: Materials with poor OI performance can be eliminated in early‑stage lab screening before running costly full‑scale fire‑response tests.

Critical caveat: An OI value alone does not quantify real‑world fire hazard. It must be combined with other fire‑response data such as heat‑release rate, smoke production and flame‑spread data for complete safety evaluation of end‑use products.

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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 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.

Q1: What is ISO 4589‑2 Oxygen‑Index (OI / LOI) test, and why is this test important for plastic materials?

A: ISO 4589‑2 measures the minimum volume‑percent oxygen in oxygen‑nitrogen mixed gas that sustains flaming combustion for vertically mounted plastic specimens under controlled ambient‑temperature laboratory conditions. OI (Oxygen Index), also named LOI (Limiting Oxygen Index). It is important because:

It delivers quantitative numeric data for comparing relative flame‑retardant performance of polymers and flame‑retardant formulations. Higher OI value = better resistance to sustained flaming.
It is widely used for incoming‑material inspection and batch‑to‑batch quality‑control for flame‑retarded plastics.
It provides small‑scale screening data before running high‑cost large‑scale fire‑safety tests.
Many material procurement specifications define minimum OI acceptance criteria referencing ISO 4589‑2.

Important note: OI lab results cannot alone represent real‑world fire hazard, and must be combined with other fire‑response data for full risk evaluationl.

Q2: What is the difference between Procedure A (Top‑surface ignition) and Procedure B (Propagating ignition) in ISO 4589‑2?A:

Procedure A (Top‑surface ignition): Apply propane flame only to the top surface end of specimen; no direct flame contact to vertical side faces. Used for specimen Type I, II, III, IV, VI (rigid bars, sheets, rolled thin‑film). Burn reference mark at 50 mm below ignition end.
Procedure B (Propagating ignition): Apply flame to top end plus ~6 mm depth of vertical side surfaces. Mandatory for flexible supported specimen Type V, optional for other specimen types, and often delivers more repeatable test data for thin (< 3 mm) self‑supporting plastics. Reference marks set at 10 mm and 60 mm from ignition end.

OI values obtained from Procedure A and B for identical material are not interchangeable. Test reports must clearly mark which ignition procedure was adopted.

Q3: OI vs LOI: Are they the same parameter in ISO 4589‑2?

A: Yes, they refer to identical physical value.

‑ OI (Oxygen Index): Preferred term inside ISO 4589 series standards.

‑ LOI (Limiting Oxygen Index): Widely‑used industry alias. Both represent minimum oxygen volume‑% sustaining flaming combustion under standard test conditions

Q4: What specimen sizes/types are defined by ISO 4589‑2? Can I test thin plastic films?

A: Six specimen forms I‑VI are specified: rigid bars, foam, as‑received sheets, electrical‑grade bars, flexible supported sheets, and Type‑VI rolled‑film specimen for very thin films (0.02‑0.10 mm). High‑shrinkage oriented thin films cannot be reliably tested as flat samples. You need to roll film using standard slitted stainless‑steel rod tool to produce self‑supporting rolled‑film specimen Form VI to minimize erratic burning and data scatter. Minimum sample quantity: at least 15 specimens; 15‑30 specimens for unknown or unstable‑burning materials.

Q5: Why do same‑material OI test results differ between labs or repeated runs?

A: Common root causes:

Gas velocity inside combustion chimney deviates from required 40 ± 2 mm/s.
Insufficient gas purging time (< 30 s) before ignition for each specimen.
Gas moisture content exceeds 0.1 % mass‑fraction; gas supply without drying treatment.
Soot deposits contaminate glass chimney, debris screen or gas diffuser.
Different specimen thickness, geometry, or mixing Procedure A / B ignition modes.
Specimens not fully conditioned; residual moisture or volatile content.
Oxygen analyser out‑of‑calibration (ISO 4589‑2 requires weekly analyser calibration).

Q6: What is the short‑procedure in ISO 4589‑2? When do I use it?

A: The short‑procedure is a pass‑fail screening test, without calculating exact OI numerical value. You test three specimens at a fixed target‑minimum‑oxygen concentration. If ≥ 2 out of three specimens self‑extinguish (“O” response), we conclude material OI ≥ specified minimum value. Otherwise, material fails threshold requirement, and full‑test Clause 8 procedure shall be performed to get precise OI value. Short‑procedure applies for quality screening only; for dispute or formal certification, full‑test procedure is mandatory.

Q7: Can ISO 4589‑2 predict real‑world fire hazard performance for finished plastic products?

A: No. ISO 4589‑2 runs small‑specimen vertical combustion under strictly‑controlled laboratory oxygen‑nitrogen flow environment. Real‑fire scenarios involve external heat radiation, mixed‑material assembly, variable ventilation, different orientation and scale effects. OI shall be treated as one input factor for full fire‑risk assessment, not standalone fire‑hazard judgment basis. It is frequently combined with UL94 vertical burning, cone calorimeter test data for complete evaluation.

Q8: What burning‑judgement criteria “O” and “X” mean in ISO 4589‑2?

A: ‑ Response “O”: Specimen self‑extinguishes before burning duration reaches 180 seconds AND burning front does not cross the specified reference mark → pass threshold at this oxygen concentration. ‑ Response “X”: Either burning time exceeds 180 seconds OR burning front travels past reference mark → material maintains sustained flaming combustion under this oxygen level. The up‑and‑down statistical testing sequence adjusts oxygen concentration based on successive “O” / “X” responses to compute final OI value.

Q9. Which materials can be tested?

A: Self-supporting vertical bars or sheets up to 10,5 mm thick — solid, laminated or cellular (foam) plastics with an apparent density of 100 kg/m³ or greater (the method may also apply to some cellular materials below that). A dedicated method is provided for flexible sheet and thin film tested while vertically supported. Materials that shrink heavily when heated (e.g. highly oriented thin film) may not give satisfactory results unless the rolled-film form (form VI) is used.

Q10. Is ISO 4589-2 the same as ASTM D2863?

A: They are technically equivalent in principle and in apparatus when direct oxygen-concentration measurement is used. Both have Procedures A (top surface ignition), B (propagating ignition) and a short procedure compared with a specified minimum OI. Differences to watch: ASTM D2863 states a density threshold of 15 kg/m³ (vs 100 kg/m³ in ISO), and there are minor differences in specimen sizes and gas-flow control details. Always test to the standard named by your customer or regulation.

Q11. How are flexible films and thin films prepared?

A: Flexible sheet (form V) is clamped by both vertical edges in a frame carrying reference marks at 20 mm and 100 mm below the top. Thin film (form VI) is wound in a 45° spiral on a 2 mm stainless-steel rod, taped while still on the rod, then the rod is withdrawn and 20 mm is cut off the top end. Rolled film gives reproducible results similar to form I and is preferred for films that otherwise shrink or burn erratically.

Q12. Can one machine cover ISO 4589-2 and ISO 4589-3?

A: Not with a standard ambient column. The high-temperature test requires a heated column that pre-heats the specimen and gas stream. UnitedTest supplies both: the YZS-100A / YZS-100B ambient oxygen index apparatus for ISO 4589-2 and ASTM D2863, and the HTYZS-100E high-temperature oxygen index apparatus for ISO 4589-3 (touch screen, imported high-accuracy oxygen sensor, up to 200 °C) — which can also be used for ambient testing.

Q13: Why choose ISO 4589‑2 Oxygen Index Tester, LOI Test Machine for Plastics & Foam from UnitedTest?

A: UnitedTest is professional manufacturer for ISO 4589‑2 oxygen‑index tester / LOI limiting‑oxygen‑index test apparatus, fully compliant with ISO 4589‑2:2017 and ASTM D2863 standards. Our LOI flammability testing machine measures oxygen‑index for plastics, rubber, foam, films, composite laminates for R&D, QC and material‑certification labs worldwide.

UnitedTest is trusted manufacturer and supplier of ISO 4589‑2 oxygen‑index tester (LOI limiting‑oxygen‑index test machine) for polymer flammability testing. Our oxygen‑index test equipment fully complies with ISO 4589‑2:2017 ambient‑temperature oxygen‑index standard, as well as equivalent ASTM D2863 test method, supporting both Procedure A top‑surface ignition and Procedure B propagating‑ignition test workflows.

The oxygen‑index (OI / LOI) test measures the minimum volume‑percentage of oxygen needed to sustain flaming combustion of vertical plastic specimens. This widely‑adopted laboratory flammability test is essential for flame‑retardant‑formula research, incoming‑goods quality‑control, batch consistency inspection, and material‑spec compliance verification across polymer industries.

UnitedTest’s ISO 4589‑2 LOI test system supports test‑specimen types I‑VI, covering rigid plastic bars, sheets, cellular foam, rubber, laminated composite, flexible thin films and rolled‑film specimens for ultra‑thin polymer films.

Core advantages for UnitedTest ISO 4589‑2 oxygen index tester

✅ Complies fully with ISO 4589‑2:2017 & ASTM D2863; supports full‑test procedure and short pass‑fail screening procedure (Clause 10).

✅ High‑precision oxygen‑analyser sensor with 0.1 % volume‑fraction resolution to meet standard measurement‑accuracy requirements.

✅ Standard transparent heat‑resistant glass combustion chimney with gas diffuser and debris‑protection screen.

✅ Complete propane flame‑igniter assembly; adjustable flame height controlled to standard 16 ± 4 mm.

✅ Accurate gas‑velocity adjustment, guarantees chimney inner gas flow at 40 ± 2 mm/s.

✅ Built‑in precise timer (accuracy ± 0.5 s) for burning‑duration recording.

✅ Supports specimen holders for self‑supporting samples and frame fixture for non‑self‑supporting flexible film specimens.

Main applications of UnitedTest oxygen‑index test machine

Our 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.

UnitedTest provides complete equipment supply, installation guidance, operation training and after‑sales technical support for ISO 4589‑2 oxygen‑index test machines. Contact us for detailed quotation and customised lab‑testing‑solution proposal for your polymer‑flammability‑testing project.

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