Glow Wire Test (GWFI, GWIT): 3 IEC 60695-2 Methods, the IEC 60335-1 Thresholds and 5 Flame Retardant Routes That Reach Them

The glow wire test presses an electrically heated wire loop against a plastic part or plaque for 30 seconds to simulate an overheated electrical contact, and it reports whether the part passes (GWEPT), the highest temperature at which the material self-extinguishes (GWFI) and the temperature at which it ignites (GWIT), three results that 5 flame retardant routes are formulated to raise. An appliance standard asks for a glow-wire flammability index of at least 850 °C and a glow-wire ignition temperature of at least 775 °C, so why can a compound that clears the first still miss the second?

The 5 flame retardant routes differ sharply in the glow-wire evidence behind them. Phosphinate systems with nitrogen synergists carry the one documented result: Clariant reports a GWFI of 960 °C and a GWIT of 775 °C for its Exolit OP 1312 blend at 15 to 20 wt% in glass-filled polyamide 66. Red phosphorus, melamine cyanurate, polymeric brominated flame retardants with antimony trioxide, and mineral and intumescent systems complete the five, but none of them has a published glow-wire value in our sources.

This page covers the heated wire, the four parts of IEC 60695-2, the three methods, the IEC 60335-1 thresholds, the 5 additive routes, the values plastics reach and a 6-step selection. Five routes among the plastic additives used in electrical compounds decide whether these numbers are reached.

The table below summarises the glow wire test in ten properties.

Standard editions are the versions current on 24 October 2026; IEC 60695-1-30 is given without an edition year because its text could not be read.

What Is the Glow Wire Test?#

The glow wire test is the IEC 60695-2 fire hazard test in which an electrically heated wire loop is held against a plastic specimen to find out whether a short-period thermal stress, such as a glowing element or an overloaded resistor, can ignite it and whether any flame it starts goes out on its own. IEC technical committee 89, Fire hazard testing, writes the series, which applies to end products and to solid electrical insulating materials.

Household appliance parts, connectors and fuse holders go through glow-wire testing alongside UL 94 and tracking tests, and carry all three results on one datasheet. The glow wire belongs to the fire group of methods for testing plastic additives, next to UL 94, LOI and the cone calorimeter.

What the glow wire simulates: an overheated contact, not an open flame#

The glow wire simulates an electrical part that has overheated, not a flame that has reached it: the heat source is a solid wire at a set temperature pressed against the plastic, so the question is whether contact heating alone can start a flame and keep it going. The test runs in the three steps listed below.

1. Heat the wire loop to the test temperature, between 550 and 960 °C depending on the requirement.
2. Press the tip against the specimen for 30 seconds, with tissue paper below to catch burning drips.
3. Withdraw the wire and observe whether the specimen ignites, how long any flame lasts, and whether drips ignite the tissue.

Contact heating changes which flame retardant property matters: additives that char or decompose endothermically at the contact point act where the heat arrives, so a system tuned for the open flame of UL 94 is not automatically tuned for a hot contact. Our sources hold no comparative glow-wire study of gas-phase against condensed-phase systems, so this is a reason to test, not a ranking.

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

The glow wire test applies a hot solid wire with no flame, while the needle flame test of IEC 60695-11-5 applies a small open flame from a needle burner, so the first asks whether an overheated contact can ignite a part and the second asks whether a small existing flame spreads across it. Product standards choose between them by the fault they guard against, and a part can be asked to pass both.

The 4 parts of IEC 60695-2 and their current editions#

Four parts of IEC 60695-2 define the glow wire test: IEC 60695-2-10:2026 specifies the apparatus and the common procedure, IEC 60695-2-11:2021 the end-product test (GWEPT), IEC 60695-2-12:2021 the glow-wire flammability index of a material (GWFI) and IEC 60695-2-13:2021 the glow-wire ignition temperature of a material (GWIT). The table below lists each part with its result, current edition and the edition it replaced.

Editions as listed on the IEC webstore on 24 October 2026. All four parts are basic safety publications of IEC technical committee 89, Fire hazard testing.

The part number decides what a datasheet value means. A value quoted as "IEC 60695-2" without a part number does not say whether it is a flammability index, an ignition temperature or an end-product severity, and a GWFI of 960 °C and a GWIT of 775 °C can describe the same compound. European and national adoptions carry the same part numbers.

Which edition of IEC 60695-2 applies in 2026?#

Since 8 May 2026 the glow-wire apparatus is specified by IEC 60695-2-10:2026, the fourth edition, while the three test methods remain at their 2021 editions: IEC 60695-2-11:2021, IEC 60695-2-12:2021 and IEC 60695-2-13:2021. The 2026 change adds a normative Annex D, "Use of pyrometer for glow-wire test", so a report dated after May 2026 can cite the new apparatus edition while quoting a GWFI or GWIT measured to the unchanged 2021 method. Datasheets that still cite the 2010 or 2014 editions refer to superseded texts.

The 3 Glow Wire Test Methods: GWEPT, GWFI and GWIT#

The 3 glow wire test methods are GWEPT, the pass or fail test on a finished product under IEC 60695-2-11, GWFI, the flammability index of a material under IEC 60695-2-12, and GWIT, the ignition temperature of a material under IEC 60695-2-13, and the last two are the numbers a flame-retardant compound carries on its datasheet. The table below compares the three by standard, specimen, result and pass definition.

Definitions paraphrased from the IEC webstore abstracts of the 2021 editions. "GWT" is used by test laboratories and instrument makers for the end-product test.

1. GWEPT (IEC 60695-2-11): the end-product test#

GWEPT, the glow-wire flammability test method for end products, is the IEC 60695-2-11:2021 test in which the finished part itself is pressed against the heated wire at a temperature set by its product standard, and it passes when the part shows a limited ability to ignite or, if it ignites, a limited ability to spread flame. Geometry and wall thickness enter the result, so a GWEPT is a property of the part, not of the material.

The end-product test is where a material's GWFI and GWIT are finally judged. A 2021 study in Polymers tested a glass-filled PBT fuse holder at 850 °C for 30 seconds against IEC 60695-2-11 and IEC 60695-2-13 and against IEC 60335-1:2020, the appliance standard that sets the requirement. IEC 60335-1 also uses the end-product test as its alternative route, a glow-wire test on the part at 750 °C with flaming of no more than 2 seconds.

2. GWFI (IEC 60695-2-12): the glow-wire flammability index of a material#

The glow-wire flammability index (GWFI) is the highest test temperature at which a material specimen either does not ignite, or ignites and goes out within 30 seconds of the wire being withdrawn, without burning away completely and without dripping onto and igniting the tissue paper underneath. The three pass conditions of IEC 60695-2-12:2021 are listed below.

• Extinction: any flame goes out within 30 s after the glow wire is removed.
• Specimen integrity: the specimen is not totally consumed.
• Drips: no burning or molten particle ignites the tissue paper below.

The highest GWFI a compound can report is 960 °C, the top of the 550 to 960 °C range, and Clariant reports exactly that for glass-filled PA66 with its Exolit OP 1312 phosphinate blend. IEC 60335-1 asks for at least 850 °C, so that result clears the appliance threshold by 110 K.

3. GWIT (IEC 60695-2-13): the glow-wire ignition temperature of a material#

The glow-wire ignition temperature (GWIT) is the temperature 25 K (30 K at the top of the temperature range) above the highest test temperature at which a material does not ignite, where a flame lasting no longer than 5 seconds for any single flame event still counts as no ignition and the specimen must not be totally consumed, as defined by IEC 60695-2-13:2021.

775 °C is the GWIT that recurs across our sources. It is the IEC 60335-1 minimum for unattended appliances, it belongs to the engineering-plastics specification set alongside UL 94 V-0 at 0.4 to 1.6 mm and a CTI of 600 V, and it is the GWIT Clariant reports for Exolit OP 1312 in glass-filled polyamide.

What is the difference between GWFI and GWIT?#

GWFI allows the specimen to ignite as long as it goes out within 30 seconds, while GWIT does not allow ignition beyond a single flame of 5 seconds, so the same compound normally reports a higher GWFI than GWIT: Clariant's Exolit OP 1312 in glass-filled PA66 reaches a GWFI of 960 °C but a GWIT of 775 °C. The 185 K gap in the Clariant example is the space between "it may catch fire but stops" and "it does not catch fire".

Why is GWIT reported 25 K above the last temperature that passed?#

GWIT is reported 25 K above the last temperature that passed because the standard defines it as the temperature at which ignition is expected, one step above the highest temperature at which the material did not ignite. A material that does not ignite at 750 °C but ignites at the next step reports a GWIT of 775 °C, which is why 775 °C is the familiar requirement value and why 750 °C is so easily misread, as the IEC 60335-1 section below explains.

How Is a Glow Wire Test Performed?#

A glow wire test is performed by heating the wire loop of an IEC 60695-2-10:2026 apparatus to the test temperature, pressing it against a plaque or a finished part for 30 seconds over a layer of tissue paper, and recording ignition, flame duration and burning drips during and after the application.

Apparatus, test temperatures and the 30-second application#

A glow wire is an electrically heated loop of resistance wire whose tip is held at a set temperature between 550 and 960 °C and pressed against the specimen for 30 seconds, and the apparatus around it exists to hold that temperature, that contact and that time constant. Its four parts are listed below.

• Wire loop: the heated element, brought to the test temperature before contact.
• Temperature measurement: traditionally at the wire tip; IEC 60695-2-10:2026 adds a normative annex on using a pyrometer.
• Specimen carriage: moves the specimen against the tip with a defined force for the 30-second application.
• Tissue paper below the specimen: the indicator for burning drips.

The wire alloy, wire diameter, contact force and penetration limit are set in IEC 60695-2-10, whose text our sources have not read, so this page states none of them.

Specimens, thickness and what to record#

A material glow-wire value is only comparable with another when the plaque thickness, the polymer grade, the glass content and the colour are stated with it, because each of them changes how much material sits under the hot wire. A 2026 study in Polymers on flame-retardant polyamide 6 tested plaques of 60 x 60 x 3.2 mm, 3 per test temperature, the specimen practice our sources record. The four items to record are listed below.

• Thickness: the plaque or wall thickness in mm.
• Material: polymer, grade and glass or filler content.
• Flame retardant system: the chemistry and its loading in wt%.
• Method and temperature: GWFI or GWIT, the standard part and the temperature reached.

A GWFI or GWIT should be quoted with the thickness it was measured at, in the same way as a UL 94 rating. Our sources contain no thickness series for any glow-wire value, so this page states no thickness effect.

Pass criteria: ignition, flaming duration and the tissue under the specimen#

Each glow wire method passes on a different criterion: GWFI tolerates a flame that goes out within 30 seconds, GWIT tolerates no flame longer than 5 seconds, and the IEC 60335-1 end-product alternative tolerates flaming of no more than 2 seconds at 750 °C. The criteria are listed below in part order.

• GWEPT: a limited ability to ignite or, after ignition, to propagate flame, at the temperature set by the product standard.
• GWFI: extinction within 30 s after the wire is removed, no total consumption, no ignition of the tissue.
• GWIT: no ignition, with a single flame of up to 5 s still counted as no ignition, and no total consumption.

The 30 seconds in the GWFI is an extinction time counted after the wire is withdrawn, not an ignition time, and the 2-second limit belongs to IEC 60335-1, not to IEC 60695-2-11.

What Does IEC 60335-1 Require? The 850 °C and 775 °C Glow-Wire Thresholds#

IEC 60335-1 requires the insulating material around current-carrying connections of an unattended household appliance to reach a glow-wire flammability index of at least 850 °C and a glow-wire ignition temperature of at least 775 °C, or the part itself to pass a 750 °C glow-wire test with flaming of no more than 2 seconds. The standard is IEC 60335-1:2020, consolidated with Amendment 1:2025 as edition 6.1 on 31 October 2025, and the thresholds sit in clause 30.2.3.

IEC 60335-1 is a product safety standard, not a regulation. Bans, furniture standards and the wider flame retardant regulations and UL/IEC requirements sit on their own page; the glow-wire clause is set out here. The table below lists the requirement element by element.

The clause number and thresholds are as recorded in our knowledge base (verified 22 September 2026). Whether Amendment 1:2025 changed clause 30.2.3 has not been checked against the amendment text.

Clause 30.2.3: unattended appliances and connections above 0.2 A#

Clause 30.2.3 of IEC 60335-1 applies to appliances that operate unattended and to the insulating parts around their connections that carry more than 0.2 A, and it asks those materials for a GWFI of at least 850 °C together with a GWIT of at least 775 °C. Both numbers apply at once, so a compound with a GWFI of 960 °C and a GWIT below 775 °C fails the material route and has to use the end-product alternative.

The pair is a material requirement, so a compounder qualifies a grade once and an appliance maker selects it across products without testing every moulding; Clariant's Exolit OP 1312 data for glass-filled PA66 answers exactly this clause.

The 750 °C end-product alternative, and why it is not a GWIT#

750 °C in IEC 60335-1 is the temperature of the alternative end-product test, in which the finished part may flame for no more than 2 seconds, not a glow-wire ignition temperature requirement, and a compound specified at "GWIT 750 °C" has been specified against the wrong number. A material whose GWIT is below 775 °C can still be used when the moulded part passes the glow wire at 750 °C with flaming of no more than 2 seconds.

Where does the confusion come from? A material that does not ignite at 750 °C reports a GWIT of 775 °C under the 25 K rule, so the two figures are neighbouring steps of one ladder. Even a 2026 study in Polymers on flame-retardant polyamide 6 calls 750 °C "the stringent ... glow-wire ignition temperature"; its data are not in question, only that wording of the requirement.

Does Amendment 1:2025 change the glow-wire clause?#

The published summary of Amendment 1:2025 lists new requirements for charging metal-ion batteries, optical radiation and cyber security, and does not mention the glow-wire clause, but the amendment text itself has not been checked, so a specification written in 2026 should be confirmed against the consolidated edition 6.1. Interpretation sheet ISH2:2025 of 12 August 2025 has not been checked against clause 30.2.3 either.

Material preselection: how GWFI and GWIT feed IEC 60695-1-30#

GWFI and GWIT feed the preselection process of IEC 60695-1-30, which uses the two material values to judge whether a material is likely to meet the end-product test of IEC 60695-2-11 before a part is moulded. Both 2021 method standards describe the two results as used together for that purpose.

How Do Flame Retardants Change GWFI and GWIT? 5 Additive Routes#

The 5 flame retardant routes that move a glow-wire result are phosphinate systems with nitrogen synergists, red phosphorus, melamine cyanurate, polymeric brominated flame retardants with antimony trioxide, and mineral and intumescent systems, and only the first has a published GWFI and GWIT in our sources: 960 °C and 775 °C in glass-filled PA66.

The first three routes are the systems of electrical polyamide, where tracking resistance is the property they trade against the fire result. All 13 types of flame retardants for plastics, with mechanisms and UL 94 loadings, are on the family hub. The table below lists the 5 routes with the glow-wire result each reaches in our sources.

Values are supplier data or study values at the stated loading in the stated polymer. A glow-wire result from one compound, one thickness and one colour does not transfer to another. "Not in our source set" means no verified value exists in our knowledge base; none is estimated.

For routes 2 to 5 our knowledge base holds the polymer, the mechanism and a UL 94 result, but no measured GWFI or GWIT. Four of the five routes are halogen-free flame retardants, which is why electrical polyamide moved to them.

1. Phosphinate systems with nitrogen synergists (DEPAL plus MPP)#

Phosphinate systems with nitrogen synergists are blends of aluminium diethylphosphinate with melamine polyphosphate, and they are the one flame retardant route with a published glow-wire result: Clariant reports a GWFI of 960 °C and a GWIT of 775 °C for its Exolit OP 1312 blend at 15 to 20 wt% in glass-filled polyamide 66.

The same loading gives UL 94 V-0 from 0.4 to 3.2 mm and a CTI of up to 600 V. Aluminium diethylphosphinate (DEPAL or AlPi, CAS 225789-38-8) carries 23.3 to 24.0 wt% phosphorus, decomposes above 300 °C and acts through PO· radical scavenging in the gas phase and charring in the condensed phase, while melamine polyphosphate (CAS 218768-84-4) adds char. Grades and the PBT data for phosphinate flame retardants (DEPAL) are on their own page.

The DEPAL route carries three costs: tracking resistance can fall (see the tracking section below), AlPi and MPP blends can bloom as a white frost after ageing at 85 °C and 85 % relative humidity, which Clariant's Exolit OP 1400 grade addresses, and Clariant has labelled the OP 1312 and OP 1314 blends Repr. 2 since 1 June 2015 because they contain more than 3 % zinc borate. Identity and regulatory status of aluminum diethylphosphinate are on its substance page.

2. Red phosphorus in glass-filled polyamide 66#

Red phosphorus is a high-efficiency phosphorus flame retardant for glass-filled polyamide 66, used in encapsulated or masterbatch form, and it is one of the three systems of electrical polyamide, although our sources hold no glow-wire value for it. Red phosphorus (CAS 7723-14-0) oxidises to phosphorus acids that promote a carbonaceous char and reaches UL 94 V-0 in glass-filled PA66 through that charring.

Its colour restricts it to dark compounds, and our sources give no loading and no GWIT, so a red-phosphorus grade is selected on the supplier's own glow-wire data at the part's thickness. Red phosphorus and the phosphinates are two of the 8 types of phosphorus flame retardants.

3. Melamine cyanurate in unfilled polyamide#

Melamine cyanurate is the nitrogen flame retardant of unfilled polyamide 6 and 66, where it reaches UL 94 V-0 as the only additive, and it is the third system of electrical polyamide, again without a glow-wire value in our sources.

Melamine cyanurate (CAS 37640-57-6) decomposes endothermically above about 300 °C and releases inert gas; its V-0 loading is not confirmed in our sources, so this page states none. Melamine itself has been on the REACH Candidate List since 17 January 2023; melamine cyanurate is not listed as such. The supplier grades and the open dosage question for melamine cyanurate are on its substance page.

4. Polymeric brominated flame retardants with antimony trioxide#

Polymeric brominated flame retardants such as brominated polystyrene are the halogenated route for glass-filled PA66 and PBT connectors, used with antimony trioxide or zinc stannates as the synergist, and our sources record no glow-wire value for them. Brominated polystyrene (CAS 88497-56-7) traps radicals in the gas phase, and its high molecular weight keeps it from blooming at the surface of an electrical part. Brominated polystyrene, PolyFR and the polyphosphonates are compared under polymeric flame retardants.

The route is narrowing: antimony trioxide (CAS 1309-64-4) carries a harmonised Carc. 2 classification (H351) under Regulation (EC) No 1272/2008, though it is not an SVHC, and Ecodesign Regulation (EU) 2019/2021 has banned halogenated flame retardants from the enclosures and stands of electronic displays since 1 March 2021.

5. Mineral and intumescent systems: where glow-wire data is missing#

Mineral and intumescent systems take polyolefins to UL 94 V-0 at loadings from 21 wt% for a PAPP:MPP intumescent to 22 to 30 wt% for APP-based grades in polypropylene, but no GWFI or GWIT for these compounds is established in our sources. How char-forming intumescent flame retardants work is set out on their own page.

Aluminium trihydrate (ATH) starts to release water at about 200 °C, below the 240 to 320 °C at which polyamides are moulded, so it is excluded from the polymer family that carries the published glow-wire values. Magnesium hydroxide (MDH) is stable to about 320 °C, but our sources give no polyamide loading for it.

A compounder targeting a GWFI of 850 °C in polypropylene therefore generates the glow-wire data on the actual compound. Loadings and surface treatments for mineral flame retardants (ATH and MDH) are on the mineral page.

Additives that pull glow-wire and tracking results apart#

A glow-wire gain can cost tracking resistance, because the flame retardant that protects the part from an overheated contact also sits in the surface that has to resist electrical tracking: 15 % aluminium diethylphosphinate took polyamide 6 from a comparative tracking index of 600 V to 550 V in the 2026 Polymers study. The three additive decisions that set the size of that trade-off are listed below.

• Zinc borate: a synergist and char promoter that also suppresses afterglow and arc tracking, and the reason the OP 1312 and OP 1314 blends contain it.
• Glass fibre: the reinforcement that wicks molten polymer in a UL 94 open-flame test, which is why a glass-filled grade needs its own flame retardant system.
• Blend design: Clariant reports a CTI of up to 600 V together with a GWIT of 775 °C for OP 1312, so the trade-off can be closed in glass-filled polyamide.

How tracking is measured, and how far each flame retardant lowers it, is set out under comparative tracking index (CTI).

Which Glow Wire Values Do Flame-Retardant Plastics Reach?#

Published glow-wire values in our sources exist for one polymer family, glass-filled polyamide, where a phosphinate blend reaches a GWFI of 960 °C and a GWIT of 775 °C; for PBT our sources record the 850 °C test condition but no material value, and for polypropylene and polycarbonate blends no value is published. The table below lists every glow-wire value and condition in our sources, by polymer.

"Not in our source set" means no verified value exists in our knowledge base. "Not established" means our sources state that no value has been published. Supplier values are at the supplier's specimen thickness, which the source does not state for the glow-wire results.

Every empty cell in Table 6 is a gap in the published evidence, not an estimate. The full matrix of flame-retardant plastics, UL 94 ratings and FR systems by polymer is on its own page.

Glass-filled nylon (PA6 and PA66)#

Glass-filled PA6 and PA66 are held to the engineering-plastics specification set of UL 94 V-0 at 0.4 to 1.6 mm, a GWIT of 775 °C and a CTI of 600 V, and a phosphinate blend at 15 to 20 wt% reaches it in Clariant's data. Loadings for every system in PA6, PA66 and high-temperature polyamides are on flame retardants for nylon.

Polyamides mould at 240 to 320 °C, which rules out ATH and narrows the field to phosphinates, red phosphorus, melamine cyanurate in unfilled grades and polymeric brominated systems. Glass content, sizing and heat ageing of glass-filled nylon are on the reinforcement page.

PBT#

Glass-filled PBT reaches UL 94 V-0 with 18 wt% of Clariant's Exolit OP 1260 phosphinate grade, and a 2021 study in Polymers tested a glass-filled PBT fuse holder at 850 °C for 30 seconds against the glow-wire methods and IEC 60335-1:2020. The study's result is not in our knowledge base. Hydrolysis and the antimony question in flame retardants for PBT and PET are covered on their own page.

Polypropylene, polycarbonate and the polymers without published glow-wire values#

Polypropylene and polycarbonate blends reach UL 94 V-0 with published loadings, 21 to 30 wt% of an intumescent in polypropylene and 20 wt% of the aryl phosphate BAPDP with 0.4 wt% PTFE in PC/ABS, but no GWFI or GWIT for either is published in our sources. A polypropylene appliance housing under IEC 60335-1 is therefore qualified on the compound itself or through the 750 °C end-product test on the moulded part. The intumescent and brominated routes to V-0, with the appliance glow-wire note, are on flame retardants for polypropylene.

How to Select a Flame Retardant System for a Glow-Wire Specification in 6 Steps#

Select a flame retardant system for a glow-wire specification in 6 steps, starting with the exact clause, method and temperature the part has to meet, because a GWFI, a GWIT and an end-product temperature lead to different formulations. The general procedure to select plastic additives by function, polymer and regulation applies here with the glow wire as the deciding test. The 6 steps are listed below.

1. Read the requirement exactly: the product standard, clause and method (for an unattended appliance, IEC 60335-1 clause 30.2.3: GWFI 850 °C and GWIT 775 °C, or 750 °C on the part).
2. Fix the polymer and its processing temperature, because polyamide at 240 to 320 °C excludes ATH.
3. Shortlist the routes that have glow-wire data in that polymer, starting with phosphinate blends in glass-filled polyamide.
4. Check the other numbers on the same datasheet: UL 94 at the part's thickness and the CTI, since a phosphinate system can cost 50 V of tracking resistance in PA6.
5. Request the supplier's GWFI and GWIT at your thickness and colour, with the standard part and edition named.
6. Test the moulded part, because the material values only preselect and the end-product test decides.

The flame retardant selector filters published dosages by polymer and UL 94 rating, with GWIT and GWFI in the test notes where a value exists.

Glow-wire selection is one part of the requirement set for electrical and electronic equipment. The full requirement set behind flame retardants for electrical and electronic equipment is on its own page.

What the Glow Wire Test Cannot Tell You#

A glow wire test cannot answer 5 questions that specifications regularly put to it, and each one has a different test behind it, as listed below.

• Whether the finished part passes: a material GWFI or GWIT preselects; only the end-product test on the moulded part decides.
• How the part behaves in an open flame: that is UL 94 or its harmonised version IEC 60695-11-10.
• Whether the surface resists electrical tracking: that is the comparative tracking index under IEC 60112.
• How much heat the part releases once it burns: that is the cone calorimeter (ISO 5660-1, ASTM E1354-26).
• How long the material lasts at service temperature: that is long-term heat ageing and the relative thermal index on a UL yellow card.

Our sources hold no study correlating GWFI or GWIT with a UL 94 rating, so a glow-wire result is never read as a prediction of a UL 94 rating, or the reverse.

Which Other Fire and Electrical Tests Sit Next to the Glow Wire Test?#

A glow-wire result is read next to 4 other tests, because checking the flammability of an electrical plastic means asking separately about a hot contact, an open flame, a tracking surface and a fully developed fire. The full map of testing plastic additives and additive-dependent properties shows which test answers which formulation question.

UL 94 flammability ratings: why a V-0 is not a glow-wire pass#

A UL 94 V-0 rating does not qualify a part for IEC 60335-1, because UL 94 asks whether a specimen stops burning after a 10-second open flame while the glow wire asks whether a hot contact ignites it at all. V-0 allows each afterflame up to 10 seconds and 50 seconds in total for 5 specimens, with no drips igniting the cotton, while V-2 allows drips that ignite it. V-0 is the strictest vertical class and the 5VA and 5VB classes use a 500 W flame; on the glow wire, a higher GWFI or GWIT is the better result. The 12 classes and their criteria are on UL 94 flammability ratings.

Comparative tracking index (CTI)#

The comparative tracking index is the voltage, up to 600 V, that a plastic surface withstands under IEC 60112 before it tracks, and it is the number traded against a glow-wire gain in electrical polyamide. Neat polyamide 6 reaches 600 V and falls to 550 V with 15 % DEPAL (Polymers, 2026). Test voltages and the flame-retardant effect are on the comparative tracking index page.

Limiting oxygen index and the cone calorimeter#

The limiting oxygen index and the cone calorimeter screen the same compounds from two other directions: the oxygen index finds the oxygen level that just sustains burning, and the cone measures how much heat a burning plaque releases. The limiting oxygen index, under ASTM D2863-23e1 and ISO 4589-2, rose from 21.0 to 30.7 vol % O2 in the 2026 Polymers polyamide 6 study with 12 wt% DEPAL plus 3 wt% synergist. The same compound cut peak heat release from 787.3 to 362.4 kW/m2 at 50 kW/m2, the measurement explained under cone calorimeter testing.

UL yellow cards and datasheet glow-wire values#

There is no separate UL glow wire test: the glow wire is an IEC method, and a datasheet reports it as an IEC 60695-2-12 GWFI or an IEC 60695-2-13 GWIT next to the UL 94 rating. What a yellow card lists, and how a compound is recognised, is on UL recognition and yellow cards.

Where can you get glow wire testing done?#

Glow wire testing is done by accredited fire-test laboratories and by the flame retardant supplier's own application laboratory, and the order should name the method part, the edition, the temperature, the specimen thickness and the product standard it serves. This page quotes no test price, because no verified figure exists in our sources.

---