UL94 Horizontal and Vertical Flammability Test for Plastics and Non-Metallic Materials

Information on the most widely used ASTM standards within the materials testing industry

Descriptions of the most prominent lSO standards within the materials testing industry

Standards including EN, DIN, JlS, and more

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Metallurgical testing examines the properties of metallic materials to determine if a particular metal is appropriate for its intended use.

Testing of polymer materials covers mechanical, thermal, and chemical properties, verifying strength, heat resistance, composition, and ensuring product quality and compliance.

UnitedTest offer world-class testing solution in testing for polymeric materials, including elastomers, thermoplastics, composites, coatings, and structural adhesives in a variety of industries.

Testing of rubber and elastomers is used to assess the various properties and performance of materials under different conditions. This is crucial for ensuring the safety, functionality, and quality of rubber and elastomer products used in industries such as automotive, construction, consumer goods, and aerospace.

Conduct adhesive testing using various testing methods to determine their performance and characteristics in applications across multiple industries such as aerospace, automotive, construction, packaging, industrial, medical, and energy, thereby supporting application development and quality assurance.

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Tensile test evaluates material resistance to stretching, measuring strength/elongation critical for quality control. UnitedTest offers universal tensile testers (10-600KN) compliant with ASTM/ISO standards, providing tailored solutions for metals, polymers, medical & industrial materials.

Compression test assesses material resistance to compressive loads, measuring strength/deformation critical for quality validation. UnitedTest offers compression testing machines compliant with ASTM/ISO standards, providing tailored solutions for concrete, plastics, metals and industrial components.

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.

Torsion Test evaluates material resistance to rotational forces, measuring torsional strength/ductility critical for fasteners, insulators, shafts. UnitedTest offers torsion testers compliant with ASTM A938/ISO 16047, providing tailored solutions for automotive, aerospace, fastener industries.

Fatigue Test assesses material durability under cyclic loading, critical for predicting service life of industrial components. UnitedTest offers fatigue testing systems (axial/bending/torsion) compliant with ASTM E466/ISO 12106, providing tailored solutions for automotive, aerospace and manufacturing sectors.

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Non-destructive Test (NDT) evaluates material/component integrity without damage, critical for safety & quality across industries. UnitedTest offers ultrasonic/X-ray/magnetic particle NDT equipment compliant with ASTM/ISO standards, plus tailored NDT solutions for aerospace, automotive & manufacturing sectors.

UL 94 Plastic Flammability Testing Machine for Device & Appliance Parts | UnitedTest

UnitedTest manufactures UL 94 compliant flammability testers. UL 94 is the safety standard for testing plastic flammability for appliance and electronic device components, evaluating polymer burning response to small open flame or radiant heat sources for material comparison and preliminary fire safety assessment.

UL 94 – Standard for Safety: Tests for Flammability of Plastic Materials for Parts in Devices and Appliances. UL 94 defines small-scale laboratory methods using standard-size specimens to measure and describe how a polymeric material responds to a small open flame or a radiant heat source under controlled conditions. This standard delivers a preliminary indication of material acceptability and provides a reliable method to compare relative burning characteristics of different plastics, or detect changes in burning behaviour before and during end-use application. It covers common classifications including HB, V0, V1, V2, 5VA and 5VB for plastic components used in electronics, household appliances and electrical enclosures. UnitedTest supplies high-precision UL 94 flammability test equipment for material R&D, incoming inspection, factory quality control and third-party certification laboratories.

Test principle

UL 94 uses standardized small‑scale flame or controlled radiant‑heat sources to simulate potential ignition risks inside electrical appliances. It quantifies observable combustion behaviours: ignition susceptibility, self‑extinguishing capacity (after‑flame, after‑glow duration), burning propagation rate, dripping of molten burning fragments, and plate burn‑through capacity.

All classifications are comparative laboratory‑derived ratings. UL 94 results cannot be mathematically extrapolated to predict large‑scale real‑fire performance directly. The standard explicitly notes real‑world fire performance is additionally governed by part geometry, assembly configuration, oxygen availability, heat‑release rate, smoke production, and combustion products, which are not fully assessed by UL 94 itself.

The Six Test Methods & Twelve Ratings

Test method	Ignition source	Ratings	Typical material
Horizontal Burning (HB)	50 W, 20 mm flame	HB	Self-supporting rigid plastics, slow-burning
50 W (20 mm) Vertical Burning	50 W, 20 mm flame	V-0 / V-1 / V-2	Rigid enclosures, structural parts (most common)
500 W (125 mm) Vertical Burning	500 W, 125 mm flame	5VA / 5VB	High-performance, burn-through resistance
Radiant Panel Index	Radiant heat panel	RP15…RP200	Surface flammability screening
Thin Material Vertical Burning	50 W, 20 mm flame	VTM-0 / VTM-1 / VTM-2	Films, flexible circuits, tapes (≤0.250 mm)
Horizontal Burning Foamed Material	50 W-class with wing tip, 38 mm flame	HBF / HF-1 / HF-2	Cellular plastics, density < 250 kg/m³

Test Specimen Information

General requirements: Specimens can be injection‑molded, compression‑molded, pultruded, or cut from sheet stock. Cut edges must be smooth, burr‑free. For material‑grade evaluation, test specimens shall cover the material’s actual used thickness range (minimum and maximum service thickness). Intermediate‑thickness specimens are mandatory if min/max‑thickness results diverge.

Dimension for main test types:

- HB / V‑0/V‑1/V‑2 bar specimen: 125 ± 5 mm × 13.0 ± 0.5 mm; thickness according to material usage (max 13 mm).

- 5VA/5VB plate specimen: 150 ± 5 mm × 150 ± 5 mm flat plaques for burn‑through assessment.

- VTM thin‑material flat blanks: 200 ± 5 mm × 50 ± 1 mm (later rolled into cylinders), thickness ≤ 0.250 mm.

- Foam HBF/HF‑series specimen: 150 ± 5 mm × 50 ± 1 mm, thickness ≤ 13 mm.

- Radiant‑panel specimen: 460 ± 3 mm × 150 ± 3 mm.

Test equipment required for UL94 Horizontal and Vertical Flammability Test for Plastics and Non-Metallic Materials

Recommend UntiedTest UL94 Horizontal & Vertical Flame Tester, consist of below:

Laboratory draft‑free fume hood / enclosure	Minimum internal volume ≥ 0.5 m³ (recommended ≥ 1 m³ for long‑burning tests); inner surfaces dark, background illuminance < 20 lx. Exhaust fan must be OFF during burning, activated post‑test for toxic‑fume removal.
Laboratory burner	Compliant with ASTM D5025; tube dimension 100 ± 10 mm length, 9.5 ± 0.3 mm inner diameter. - A wing‑tip burner attachment for foam HBF/HF‑series test. - Burner‑tilting fixture for 500 W 5V‑tests to set burner angle at 20° offset from vertical axis.
Ring stand + clamp	specimen holders, wire gauzes for HB test and foam test; special flexible‑specimen support fixture for sagging HB samples.
Timing device	resolution accurate to 0.1 second.
Gas supply	Technical‑grade methane (≥ 98 % purity); mass‑flowmeter or calibrated rotameter (accuracy ± 2 %), manometer for back‑pressure monitoring. - 50 W test: gas flow 105 ± 5 mL/min, back‑pressure < 10 mm water column. - 500 W test: gas flow 965 ± 30 mL/min, back‑pressure 125 ± 25 mm water column.
Other tools	1. Indicator cotton: 100 % absorbent cotton (max 0.08 g for V‑/VTM‑tests; max 0.18 g for foam tests). 2. Mandrel (Φ 12.7 ± 0.5 mm rod) plus pressure‑sensitive adhesive tape: for preparing rolled cylindrical VTM thin‑film specimens.

Key Test Parameters

Test Mode	Flame Power	Flame Height	Main Measured Parameters
HB Horizontal	50 W	20 ± 1 mm blue flame	burning rate (mm/min); stop‑burn position relative to reference marks
V‑0/V‑1/V‑2 Vertical	50 W	20 ± 1 mm blue flame	t₁(first‑ignition after‑flame), t₂(second‑ignition after‑flame), t₃(after‑glow); total cumulative burn‑time; cotton ignition from drips; burn‑to‑clamp
5VA/5VB Vertical	500 W	total height 125 ± 10 mm; inner blue cone 40 ± 2 mm	repeated 5‑cycle flame application; after‑flame / after‑glow; dripping ignition; plate burn‑through
VTM thin‑material	50 W	20 ± 1 mm	same time‑metrics as V‑series for rolled tubular samples
HBF/HF‑foam	500 W wing‑tip flame	38 ± 2 mm blue flame	horizontal burning rate; after‑flame/after‑glow duration; drip‑ignition of cotton
Radiant Panel	Radiant heat source (ASTM E162‑08)	non‑flame	radiant‑panel‑index value for surface flame spread

Test procedure of UL94 Horizontal and Vertical Flammability Test for Plastics and Non-Metallic Materials

1. Machine specimens to standard dimensions; prepare two groups of samples for Condition‑A and Condition‑B pre‑conditioning according to clause 6.

2. Adjust and calibrate burner gas flow, back‑pressure and flame geometry. Perform periodic flame‑verification per ASTM D5207 (monthly or after gas‑source /‑equipment change).

3. Mount specimen vertically in clamp (clamp the upper 6 mm of bar); place absorbent cotton indicator 300 ± 10 mm below specimen bottom edge.

4. Apply standardized flame to specimen bottom edge for defined duration, retract burner, start timer to record first after‑flame time t₁.

5. Immediately re‑apply flame for second specified duration after t₁ finishes, retract burner, record second after‑flame t₂ and after‑glow t₃.

6. Observe and log whether cotton is ignited by flaming drips; observe if combustion propagates up to holding clamp.

7. Complete full specimen set, ventilate hood after each specimen run.

8. Evaluate raw data against classification table; apply retest rule if borderline or single‑specimen‑failure appears.

9. Compare ratings from Condition‑A and Condition‑B batches, assign the lower performance as the official UL 94 classification for that material‑thickness combination.

Industry Application Fields

UL 94 applies for polymeric components inside electrical, electronic and household appliances: connectors, housing enclosures, internal mechanical plastic parts, insulators, circuit‑board substrates, instrument housings, low‑voltage device components.

It is for device‑component materials and explicitly excludes building‑construction materials such as wall/floor covering, furniture decorative articles.
For extremely tiny components (total volume < 2500 mm³) which cannot be machined to UL‑94 standard‑specimen dimensions, UL 1694 shall be used instead of UL 94 for flammability assessment.

Related Test Standard:

IEC 60695‑11‑10	50 W horizontal & vertical flame test methods
UL 94	Widely‑used North‑American standard for plastic flammability (HB horizontal burn; V‑0/V‑1/V‑2 vertical burn). Its test setup and evaluation criteria are highly analogous to ISO 1210 / IEC 60695‑11‑10.
ASTM D635	US horizontal‑burning rate test for plastics (similar to ISO 1210 Method A).
ISO 1210	Plastics; determination of the burning behaviour of horizontal and vertical specimens in contact with a small-flame ignition source
IEC 60695‑11‑20	500 W flame (5V classifications), the "bigger flame" counterpart.
ISO 9773	vertical burning of thin flexible films/sheets (for materials that shrink away, which ISO 1210 cannot handle).
ISO 9772	cellular plastics, horizontal small‑flame burning.
ASTM D3801	vertical, 20 mm flame
ASTM D4804	thin flexible
GB/T 2408 (China), AS/NZS 60695.11.10, JIS C 60695‑11‑10, UNE‑EN 60695‑11‑10 — national adoptions of IEC 60695‑11‑10.

Keywords: UL 94,UL94 flammability tester,plastic material flammability test,appliance plastic flame test,electronic device plastic burning test,polymer material fire response test,UL94 V0 V1 V2 HB test,5VA 5VB flammability classification,small scale flame test for plastics,radiant heat source burning test,UnitedTest UL94 testing machine,plastic fire safety test instrument,electrical enclosure plastic flammability test,flame retardant plastic lab test,plastic material burning characteristic tester

UL94 horizontal vertical flame tester, standard UL94 flammability test chamber for plastic, rubber, foam, electronic material fire resistance test, supports HB/V0/V1/V2/5VA/5VB/VTM/HBF test grades, PLC touch screen automatic timing, 50W & 500W dual burner, 1-year full warranty, factory direct export

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.

Q1. What is the UL 94 test?

UL 94 is the international benchmark standard — Tests for Flammability of Plastic Materials for Parts in Devices and Appliances — that defines how a plastic or other non-metallic material reacts to a small open flame or radiant heat source under controlled laboratory conditions. Published by ULSE Inc. and approved as an American National Standard (ANSI/UL 94), it is currently in its 7th Edition (dated February 28, 2023, with revisions through January 5, 2024). It grades materials into 12 classifications produced by 6 test methods.

Q2. Why is the UL 94 test important?

Because it answers the one question a product safety engineer cannot guess: if this plastic is ignited by an internal electrical fault, will it put itself out, or will it keep burning and drip fire onto everything below it? Four concrete reasons:

Market access — a UL 94 rating (recorded on the UL Yellow Card) is normally the minimum gate for any polymer used in or near live electrical parts. Without it, a compound cannot be designed into certified equipment.
Fire safety — it separates materials that self-extinguish without flaming drips (V-0, 5VA, VTM-0, HF-1) from those that sustain flaming or shed burning droplets, which is the main fire-spread mechanism inside a sealed enclosure.
Comparative screening — it is fast and cheap, so it is the industry's common language for comparing compounds, flame-retardant packages, colours and wall thicknesses.
Ongoing quality control — Annex A (Follow-Up Inspection) and Annex B (alternate manufacturing sites) turn the rating into a living qualification, so a formulation or process drift cannot silently downgrade the material.

Q3. Which industries require UL 94 testing?

Consumer electronics and IT/AV equipment, household and commercial appliances, electrical distribution and industrial control (breakers, terminal blocks, connectors), lighting, automotive and e-mobility (connectors, battery-module insulators, charging equipment), wire & cable, flexible printed circuits, insulating tapes and films, and low-density gasket/acoustic/packaging foams.

Q4. What is the difference between V-0, V-1 and V-2?

All three use the same 50 W (20 mm) vertical flame, two 10-second applications, and five specimens. The difference is how much burning is tolerated:

Criterion	V-0	V-1	V-2
Afterflame per specimen (t₁ or t₂)	≤ 10 s	≤ 30 s	≤ 30 s
Total afterflame for 5 specimens	≤ 50 s	≤ 250 s	≤ 250 s
Afterflame + afterglow (t₂+t₃)	≤ 30 s	≤ 60 s	≤ 60 s
Burning up to the holding clamp	No	No	No
Cotton ignited by flaming drips	No	No	Yes

Q5. What is the difference between 5VA and 5VB?

Both use the 500 W (125 mm) flame applied five times for 5 seconds (bars) and to the centre of a 150 × 150 mm plate. Afterflame + afterglow must be ≤ 60 s and no drips may ignite the cotton. The decisive difference is burn-through: 5VA = the plate is NOT burned through (no visible flame on the opposite face, and no opening > 3 mm after cooling 30 s); 5VB = burn-through is permitted (or plates were not tested). 5VA/5VB materials must also meet V-0 or V-1 at the same thickness.

Q6. What does HB mean, and when is it used?

HB (Horizontal Burning) is the entry-level rating, assessed in the horizontal position. A material qualifies if the burning rate is ≤ 40 mm/min over a 75 mm span for 3–13 mm thickness, or ≤ 75 mm/min below 3.0 mm, or if it stops burning before the 100 mm reference mark. Useful bonus rule: a rating obtained at 3.0 ± 0.2 mm automatically extends down to 1.5 mm.

Q7. Is VTM-0 the same as V-0?

No — never substitute one for the other. V-0 applies to rigid, self-supporting bars ignited twice for 10 s. VTM-0 applies to thin films that are rolled into a lapped cylinder around a 12.7 mm mandrel and ignited twice for only 3 seconds. The time limits look similar, but UL Solutions is explicit that the methods are fundamentally different and the ratings are not interchangeable. A specification calling for V-0 cannot be satisfied with a VTM-0 material.

Q8. What are the standard specimen sizes?

HB / V / 5V bars: 125 ± 5 mm × 13.0 ± 0.5 mm, at minimum (and maximum) thickness, max 13 mm, corner radius ≤ 1.3 mm
5V plates: 150 ± 5 mm × 150 ± 5 mm
VTM films: 200 ± 5 mm × 50 ± 1 mm, ≤ 0.250 mm thick, rolled around a 12.7 ± 0.5 mm mandrel
HBF foam: 150 ± 5 mm × 50 ± 1 mm, max 13 mm
Radiant panel: 460 ± 3 mm × 150 ± 3 mm

Q9. How many specimens are needed?

Two sets per conditioning condition: 2 × 3 (HB), 2 × 5 (V, VTM, HBF/HF), and 2 × 5 bars + 2 × 3 plates (5V). The final rating is the lower class obtained from the two conditioning conditions.

Q10. How is the V-0/V-1/V-2 test actually performed?

Clamp the bar at its upper 6 mm, vertical, with the lower end 300 ± 10 mm above a cotton indicator (≤ 0.08 g absorbent 100 % cotton, ~50 × 50 mm, ≤ 6 mm thick). Apply the 20 ± 1 mm blue flame with the burner top 10 ± 1 mm below the specimen's bottom edge for 10 ± 0.5 s, withdraw at ~300 mm/s to ≥ 150 mm and start timing afterflame t₁. The instant flaming ceases, re-apply the flame for another 10 ± 0.5 s, then record t₂ (afterflame) and t₃ (afterglow). If the specimen drips, tilt the burner to 45 ± 5° so molten material does not fall into the barrel.

Q11. What is the 500 W (5VA/5VB) procedure?

Methane at 965 ± 30 ml/min with a back pressure of 125 ± 25 mm water produces a flame 125 ± 10 mm tall with an inner blue cone of 40 ± 2 mm, with the burner tube inclined 20 ± 5° from vertical. The blue-cone tip is held 0–3 mm from the specimen. Bars receive five applications of 5 ± 0.5 s, each separated by 5 ± 0.5 s; plates are flame-attacked at the centre of the bottom surface and then inspected for burn-through.

Q12. Why is there a cotton pad under the specimen?

The cotton is a drip indicator. If the specimen sheds flaming particles or molten droplets that ignite the cotton, the material cannot be V-0/V-1/5VA/5VB/HF-1 — it drops to V-2 or HF-2 (or fails). It simulates the realistic hazard of burning debris igniting materials below the part inside a product.

Q13. What is the Radiant Panel Index test, and when is it used?

UL 94 §10 refers to ASTM E162-08: a 460 × 150 mm specimen is exposed to a calibrated radiant heat panel and the surface flame-spread index is measured. It is assigned as the average of 4 specimens (6 if the average is < 50), rounded to the nearest multiple of five → RP15, RP25, RP50, RP75, RP100, RP150, RP200. It is the only UL 94 method using radiant heat rather than a flame, and it is exempt from the 13 mm / 1 m² limits of the other methods.

Q14. What flame heights and gas flows are specified?

Test	Flame height	Methane flow	Back pressure
HB, V, VTM (50 W)	20 ± 1 mm blue flame	105 ± 5 ml/min	< 10 mm water
5VA / 5VB (500 W)	125 ± 10 mm, inner cone 40 ± 2 mm	965 ± 30 ml/min	125 ± 25 mm water
HBF / HF-1 / HF-2 (wing tip)	38 ± 2 mm	965 ± 30 ml/min	50 ± 10 mm water

Q15. Why does the standard specify ≥ 98 % methane?

Flame temperature, shape and heat flux depend on gas composition. Technical-grade methane (≥ 98 %) is the reference fuel; substituting propane or LPG changes the flame and invalidates comparability with the ASTM D5207 confirmation data.

Q16. What burner angles are used?

0° (vertical, for V/VTM), 20° ± 5° (500 W 5VA/5VB), and 45° ± 2° (HB flame application to the specimen end; 45° ± 5° when tilting the burner away from drips in V and VTM). A quality tester lets the operator switch or lock these angles precisely.

Q17. Why must the chamber interior be dark and the fan be switched off during the test?

A dark background (< 20 lx) makes the small blue flame and the flame front visible so afterflame/afterglow can be timed accurately. The exhaust fan is turned off during the test so that no draught disturbs the flame or the oxygen supply, then on immediately after to remove toxic combustion products. Note: chambers smaller than 1 m³ may not give consistent results when burning times are prolonged.

Q18. How does UL 94 relate to IEC 60695 and ASTM methods?

They are technically equivalent counterparts, listed in §2.2:

HB ↔ ASTM D635 ↔ IEC 60695-11-10
V-0/V-1/V-2 ↔ ASTM D3801 ↔ IEC 60695-11-10
VTM ↔ ASTM D4804 ↔ ISO 9773
5VA/5VB ↔ ASTM D5048 ↔ IEC 60695-11-20
HBF/HF-1/HF-2 ↔ ASTM D4986 ↔ ISO 9772
Radiant Panel Index ↔ ASTM E162-08
Burner and flame confirmation: ASTM D5025 / D5207 ↔ IEC TS 60695-11-3 / -11-4 ↔ ISO 10093

Q19. Can one machine cover all UL 94 methods?

Yes — a well-designed UL 94 horizontal & vertical flammability test chamber covers HB, V-0/V-1/V-2, 5VA/5VB, VTM and HBF/HF-1/HF-2 by changing the burner (standard / wing tip), the burner angle (0°/20°/45°) and the specimen fixtures. This is the configuration most third-party labs and material producers buy, because it avoids five separate purchases.

Q20. What should I prepare before requesting a quotation?

Tell the supplier: which UL 94 ratings you need (HB / V / 5V / VTM / HBF), specimen thickness range, preferred chamber volume, gas type available on site (methane ≥ 98 %), power supply, exhaust/ventilation conditions, whether you need automated timing and report output, and whether you also need related tests (glow-wire IEC 60695-2-10/11/12/13, oxygen index ISO 4589, ISO 3795 / FMVSS 302 automotive horizontal burning).

Q21. Why choose UnitedTest for UL 94 flammability test equipment?

UnitedTest is a global manufacturer of materials and structural testing equipment, with a product range spanning universal testing machines, dynamic/fatigue testers, impact testers, rheology instruments, HDT/Vicat systems, torsion testers and custom-engineered testing systems. That breadth matters for a flammability lab: the same supplier can deliver the UL 94 chamber, the specimen preparation and dimensional metrology tools, the mechanical property machines used for material development, and fully customised fixtures or chambers — with one service team, one software ecosystem and one calibration chain.

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