Plastic Needle Flame Test (IEC 60695-11-5): Standards, Procedure, and Applications

The plastic needle flame test is a standardized fire hazard assessment that determines whether plastic materials, components, and finished product parts will ignite, sustain combustion, or spread flame when exposed to a small, controlled flame typical of internal electrical fault conditions. Performed in accordance with IEC 60695-11-5 and its equivalent national standards such as GB/T 5169.5 and EN 60695-11-5, the test is widely required for the safety compliance of electrical and electronic products. This article explains the test principle, sample requirements, methodology, acceptance criteria, and typical industrial applications.

Technical Overview

The needle flame test is a small-scale fire hazard test defined in IEC 60695-11-5 (Fire hazard testing — Part 11-5: Test flames — Needle-flame test method — Apparatus, confirmatory test arrangement and guidance). It simulates the small flame that may arise from fault conditions inside electrical equipment, such as flashover, tracking currents, overloaded components, or arcing at damaged connections. During the test, a miniature butane flame of defined height is applied directly to a plastic specimen or component for a specified duration, and the specimen's ignitability, burning behavior, and ability to self-extinguish are evaluated.

The needle flame test complements other fire hazard tests in the IEC 60695 series, including the glow-wire tests (IEC 60695-2-10 to IEC 60695-2-13) and the horizontal and vertical burning tests for materials (IEC 60695-11-10 and IEC 60695-11-20, related to the UL 94 classification system). In China, the equivalent national standard is GB/T 5169.5, which is technically aligned with the IEC method. Product safety standards such as IEC 60335-1, IEC 60598-1, IEC 60947-1, and IEC 62368-1 frequently specify the needle flame test for parts that cannot be assessed by material pre-selection alone.

• Burner: needle-shaped tube with an internal orifice of 0.5 mm ± 0.1 mm
• Test gas: butane with a purity of at least 95%
• Flame height: 12 mm ± 1 mm
• Typical flame application times: 5 s, 10 s, 15 s, 20 s, 30 s, 60 s, or 120 s, as specified by the relevant product standard

Testing Samples

Plastic Materials and Molded Test Plates

Thermoplastics and thermosets such as ABS, PC, PA, PBT, PP, PVC, PET, phenolics, and epoxy-based compounds can be evaluated either as finished parts or as molded plates. When material-level assessment is required, specimens are prepared in dimensions and thicknesses agreed with the customer or specified by the applicable product standard, since burning behavior is strongly thickness-dependent.

Electronic and Electrical Components

Frequently tested items include connectors, terminal blocks, switches, relays, coil bobbins and formers, fuse holders, cable clips, LED holders, printed circuit boards, and insulating sleeves. Components are tested in their delivered state, because geometry, surface finish, contamination, and proximity of adjacent parts all influence the result.

Finished Product Parts and Sub-assemblies

Enclosures, internal barriers, insulating bushings, fan blades, decorative trims, and supports from appliances, luminaires, power supplies, and information technology equipment can be assessed. Where possible, such parts are mounted in their normal installation orientation so that the flame impinges on the surface considered most at risk in actual service.

Testing Items

During a needle flame test, the laboratory records and reports the following observations:

• Whether the specimen ignites when the flame is applied
• Afterflame and afterglow time, i.e., the duration of burning or glowing after removal of the test flame
• Whether flaming or glowing drops or particles fall from the specimen
• Whether the layer of wrapping tissue placed beneath the specimen is ignited (an indicator of fire spread)
• The extent of charring, melting, or deformation of the specimen and any adjacent parts
• The final conformity judgment (pass or fail) against the criteria of the applicable product standard

Testing Methods

Apparatus and Test Conditions

The test uses a needle burner consisting of a tube at least 35 mm long with an internal orifice of 0.5 mm ± 0.1 mm, supplied with butane gas of at least 95% purity. The flame height is adjusted and verified at 12 mm ± 1 mm before each series of tests. The test is conducted in a draught-free enclosure under standard atmospheric conditions: ambient temperature of 15 °C to 35 °C, relative humidity of 45% to 75%, and air pressure of 86 kPa to 106 kPa. The burner is normally inclined at approximately 45° to the horizontal so that the flame tip contacts the selected point on the specimen.

Specimen Preparation and Conditioning

Specimens are cleaned and conditioned, typically for at least 24 hours, under the standard atmospheric conditions described above unless otherwise specified. A minimum of three specimens is generally tested for each configuration. Beneath the specimen, a single layer of soft wrapping tissue is laid on a smooth white pine board, positioned about 200 mm ± 5 mm below the point of flame application, to detect any falling burning debris.

Test Procedure

The specimen is fixed in the worst-case orientation, and the calibrated needle flame is applied to the designated point for the duration specified in the relevant product standard, commonly between 5 s and 120 s. The operator observes and times any ignition, flame propagation, flaming drips, and the behavior of the tissue and board. Observation continues after the burner is withdrawn until all combustion and glowing cease, or for the period defined by the standard.

Acceptance Criteria

Typical conformity criteria, as referenced in IEC 60695-11-5 and common product standards, are as follows:

• The specimen does not ignite; or
• If the specimen ignites, the flame or glowing extinguishes within 30 s after removal of the test flame, without ignition of the wrapping tissue; and
• No fire spreads to adjacent parts or to the surrounding area of the equipment in a manner that would create a hazard.

Applications

The needle flame test is applied throughout the electrical and electronics industry for product development, incoming quality control, and third-party certification support. Accredited third-party laboratories routinely perform this test for manufacturers seeking compliance with international safety schemes.

• Household and similar electrical appliances (IEC 60335 series)
• Luminaires and lighting chains (IEC 60598 series)
• Audio/video, information technology, and communication equipment (IEC 62368-1)
• Low-voltage switchgear and controlgear (IEC 60947 series)
• Electrical accessories such as plugs, socket-outlets, and switches (IEC 60884 series)
• Medical electrical equipment (IEC 60601 series)
• Transformers, motors, relays, and other component-level products
• Plastic compound development, flame-retardant formulation screening, and batch quality verification

FAQ

What is the difference between the needle flame test and the glow-wire test?

The needle flame test applies an actual small butane flame to the specimen and simulates flaming fault conditions, whereas the glow-wire tests (IEC 60695-2 series) press an electrically heated wire at temperatures between 550 °C and 960 °C against the specimen to simulate glowing hot components. The two methods are complementary, and product standards specify which one applies to each part.

Which standards govern the plastic needle flame test?

The core method is defined in IEC 60695-11-5, with equivalent or aligned national editions such as GB/T 5169.5 and EN 60695-11-5. Numerous end-product standards, including IEC 60335-1, IEC 60598-1, IEC 60947-1, and IEC 62368-1, reference the needle flame test for specific components and situations.

How long is the flame applied to the specimen?

The application time is defined by the relevant product standard and commonly ranges from 5 s to 120 s. Shorter durations are typical for small components, while longer durations are specified for parts in more demanding positions. If no duration is specified, the test is usually performed with a commonly accepted default and clearly reported.

How many samples are required for testing?

A minimum of three identical specimens is generally recommended so that variability in burning behavior can be assessed. For finished parts, the number may be increased depending on the product standard or the number of distinct flame application points.

Can the needle flame test replace a UL 94 or IEC 60695-11-10 material rating?

No. The needle flame test evaluates the behavior of a specific part or material configuration under a small flame, while UL 94 and IEC 60695-11-10/11-20 classify raw materials using standardized horizontal or vertical burning procedures. The two approaches serve different purposes, and many certification schemes require both part-level and material-level evidence.

What happens if the specimen fails the test?

If the specimen ignites and does not self-extinguish within the allowed time, or if the tissue paper is ignited, the part is considered non-compliant. Remedies include selecting a higher flame-retardancy material grade, increasing wall thickness, adding barriers, or redesigning the part to reduce exposure to potential ignition sources, followed by re-testing at an accredited third-party laboratory.