Cone Calorimeter Testing: ISO 5660-1 and ASTM E1354, 8 Results and How 5 Flame Retardant Systems Change Them

A cone calorimeter is a bench-scale fire test that burns a 100 x 100 mm plastic specimen under a set radiant heat flux and calculates how fast it releases heat from the oxygen the flame consumes, and its 8 results are the numbers that 5 families of halogen-free flame retardant systems are formulated to move. Neat polypropylene reaches a peak heat release rate of 1,148 to 1,332 kW/m2 at 35 kW/m2, and the same polymer with 25 wt% of an intumescent system stays at 220 to 255 kW/m2 (Yin et al., Beijing Institute of Technology, 2026). So why can the flame retardant that cuts the peak by 78 to 84 % barely move the time to ignition, and what does that mean for a compound that still has to pass UL 94?

Each flame retardant system leaves its own signature on a cone report. Intumescent systems in polypropylene collapse the peak and leave char; phosphinates with a P/N synergist in polyamide 6 cut the peak while raising smoke; the mineral flame retardants ATH and MDH delay the ignition of EVA/LLDPE cable compound; expandable graphite cuts the peak of polyurethane foam; and nanofillers such as organoclay act as barrier synergists.

The sections below run from the oxygen-consumption principle and the ISO 5660-1 and ASTM E1354-26 method to the 8 results, typical values, the 5 systems, two reading rules, the specifications that use heat release and the test's limits. Five families of plastic additives that act as flame retardants are judged on these numbers.

The cone calorimeter's method, outputs and limits fit in 10 rows.

Standard editions are the versions current on 24 October 2026. Every pHRR on this page is given with the heat flux it was measured at.

What Is a Cone Calorimeter?#

A cone calorimeter is an oxygen consumption calorimeter that exposes a flat specimen to a controlled radiant heat flux from a cone-shaped electric heater, ignites the gases it gives off with a spark, and measures how fast it releases heat, the method standardised as ISO 5660-1 and ASTM E1354-26.

Why measure heat release rather than whether a plastic ignites at all? NIST gives the answer: "Heat release rate is the most important thing to know about a fire." In NBS Special Publication 749 (Babrauskas et al., National Bureau of Standards, 1988), flame-retarded products gave more than 15 times the available escape time and about one quarter of the heat release of non-flame-retarded products in room tests.

How oxygen consumption calorimetry works#

Oxygen consumption calorimetry works because burning organic materials release almost the same amount of heat for every kilogram of oxygen they consume, about 13.1 MJ (13.1 kJ per gram), so measuring the oxygen missing from the exhaust gives the heat the specimen is releasing at each second of the test. The calculation runs in 3 steps.

1. Draw the combustion gases into an exhaust hood above the burning specimen and measure the flow.
2. Measure how much oxygen is missing from that flow compared with incoming air.
3. Multiply the oxygen consumed by about 13.1 MJ per kg and divide by the 0.01 m2 exposed area, which gives the heat release rate in kW/m2.

William Thornton of Armstrong College in England, now Newcastle University, recognised the oxygen-heat relationship in 1917, and Clayton Huggett of the US National Bureau of Standards turned it into a working constant in a 1980 paper in Fire and Materials, building on foundations laid with William Parker.

Who built the cone calorimeter#

The cone calorimeter was built by Vytenis Babrauskas and colleagues at the Center for Fire Research of the US National Bureau of Standards, now NIST, who first described it in November 1982. It won an R&D 100 Award in 1988, became commercially available from the mid-1980s, and NIST now counts more than 300 cones in service worldwide. Alexander Morgan of the University of Dayton, quoted on the NIST museum page, calls it "the most important tool ever created in the field of fire safety science".

Is a cone calorimeter the same as a bomb calorimeter?#

No: a bomb calorimeter burns a small sample completely in pressurised oxygen inside a sealed steel vessel and reports how much heat it contains, while a cone calorimeter burns a flat specimen in open air under radiant heat and reports how fast that heat is released, which is what decides how a fire grows.

How Is a Cone Calorimeter Test Run? ISO 5660-1 and ASTM E1354#

A cone calorimeter test is run by placing a 100 x 100 mm specimen horizontally under the conical heater at a fixed heat flux, igniting its decomposition gases with an electric spark, and logging heat release, mass and smoke every second until flaming stops, as set out in ISO 5660-1:2015 and ASTM E1354-26. The cone calorimeter sits in the fire group of the methods for testing plastic additives, next to the oxygen index and UL 94. A cone run follows 5 steps.

1. Cut or mould the specimen to a 100 x 100 mm face; plastics research uses 3 to 3.2 mm plaques.
2. Set the heater to the chosen heat flux, usually 35 or 50 kW/m2.
3. Place the specimen horizontally on the load cell and position the spark igniter above it.
4. Record the time to sustained flaming, then heat release rate, mass and smoke obscuration through the burn.
5. Report every result with the flux, the thickness and the number of replicates.

ASTM states the limit of the method in its own scope.

Specimen, orientation and ignition#

Four specimen settings decide whether two cone results can be compared: the face size, the thickness, the orientation and the surface. The four settings are listed below.

• Face: 100 x 100 mm, which makes the exposed area 0.01 m2.
• Thickness: 3 mm in the polypropylene study and 3.2 mm in the polyamide 6 study, always reported, because a thicker plaque burns longer.
• Orientation: horizontal, under an electric spark igniter; ASTM E1354-26 reserves vertical mounting for exploratory or diagnostic work.
• Surface: planar or nearly planar; the ASTM method does not apply to end-use products without such a surface.

Two cone results should only be compared when the specimens had the same thickness, orientation and heat flux.

Heat flux: why 35 or 50 kW/m2#

Most plastics are tested at 35 or 50 kW/m2: 35 kW/m2 is the typical flux NIST names for the instrument and the one most polyolefin flame retardant studies use, and 50 kW/m2 is the higher exposure used for more fire-resistant materials such as flame-retarded polyamides.

The heat flux is part of the result. Neat polypropylene at 35 kW/m2 (1,148 to 1,332 kW/m2) and neat polyamide 6 at 50 kW/m2 (787.3 kW/m2) cannot be ranked against each other. ASTM E1354-26 clause 1.4 sets initial test heat fluxes at 0 to 100 kW/m2, not the 10 to 100 kW/m2 that circulates in online summaries. A pHRR should always be reported with the heat flux it was measured at.

ISO 5660-1 and ASTM E1354: current editions and scope#

Two standards define the cone calorimeter test: ISO 5660-1:2015, amended in 2019, which covers heat release rate by the cone calorimeter method and the dynamic smoke production rate, and ASTM E1354-26, which covers heat and visible smoke release rates using an oxygen consumption calorimeter. ASTM E1354-26 was last updated on 5 August 2026 and supersedes E1354-25, so a data sheet quoting E1354-17 or older cites an inactive version. ISO 5660-1:2015 is the third edition, and its Amendment 1:2019 replaces clause 6.10 on the ignition circuit.

The two standards share the oxygen-consumption method and differ in title, scope wording and edition history.

Where a cell says "not read", the standard's own text was not available to us and no value is given.

Five further standards use the cone: ASTM D5485, NFPA 271 and CAN/ULC-S135 (named by NIST), and ASTM D6113 and ASTM E1740 (listed by test laboratories).

Does ISO 5660-1 measure smoke as well as heat release?#

Yes: ISO 5660-1:2015 covers both the heat release rate and the smoke production rate, measured dynamically in the exhaust duct while the specimen burns, and ASTM E1354-26 measures visible smoke the same way, by the obscuration of a light beam by the combustion gases. Dynamic cone smoke and the specific optical density from a closed chamber under ISO 5659-2 or ASTM E662 are different measurements, so a specification that names one is not met by a result from the other.

What Does a Cone Calorimeter Measure? 8 Results on One Test Report#

A cone calorimeter report carries 8 results: time to ignition, the heat release rate curve and its peak, total heat release, mass loss rate, effective heat of combustion, smoke production, char residue, and derived indices such as MARHE, and the peak heat release rate is the one flame retardants are judged on. Each of the 8 results answers a different question about how a plastic burns.

Values are from the cited studies at the stated heat flux and thickness. Results measured at different fluxes are never compared on this page.

1. Time to ignition (TTI)#

Time to ignition is the time from the moment the specimen is first exposed to the heater until it sustains flaming, the quantity ASTM E1354-26 calls ignitability, reported in seconds. Under 50 kW/m2 on 3.2 mm plaques, neat polyamide 6 ignited at 102 s, the same polymer with 15 wt% of aluminium diethylphosphinate (ADP) at 77 s, and with 12 wt% ADP plus 3 wt% of a synergist at 63 s (Peng et al., Beijing University of Chemical Technology, 2026). Why would a flame retardant make a plastic ignite sooner?

2. Heat release rate (HRR) and its peak (pHRR)#

Heat release rate is the heat a burning specimen releases per second per square metre of exposed surface, calculated from oxygen consumption and reported in kW/m2, and its peak, pHRR, is the highest value on that curve and the single number flame retardants are most often compared on.

Polypropylene shows why a neat value is a range: homopolymer, random and block copolymer peaked at 1,148, 1,182 and 1,332 kW/m2 (35 kW/m2, 3 mm), and 25 wt% of an intumescent system brought them to 255, 240 and 220 kW/m2, cuts of 77.8, 79.7 and 83.5 % (Yin et al., 2026). Polyamide 6 at 50 kW/m2 on 3.2 mm plaques fell from 787.3 to 549.0 kW/m2 with 15 wt% ADP and to 362.4 kW/m2 with ADP plus synergist, cuts of 30.3 and 54.0 % (Peng et al., 2026).

How do you read a heat release rate curve?#

Read a heat release rate curve by its four features in time order: when it starts, how high it peaks, how long it stays up, and how much area it encloses, because each one changes differently when a flame retardant is added. Schartel and Hull's 2007 Fire and Materials paper is the reference work on interpreting such curves. The four features are listed below.

• Onset: the time to ignition, where the curve leaves zero.
• Peak: the pHRR, the height of the highest point.
• Shape after the peak: a sharp single peak for a non-charring polymer, a lower and broader curve when a protective char forms.
• Area: the total heat release, the integral of the curve over the test.

3. Total heat release (THR)#

Total heat release is the area under the heat release rate curve, the total energy the specimen gives off per square metre over the test, reported in MJ/m2. The intumescent system cut polypropylene's total by 23.8 to 26.9 % at 35 kW/m2 (164 to 125 MJ/m2 for the homopolymer), and phosphinate cut polyamide 6 by 12.0 and 15.5 % at 50 kW/m2 (122.0 to 107.3 and 103.1 MJ/m2). Against peak cuts of about 80 % and up to 54 %, both flame retardants can spread much of the same fuel over a longer, lower burn rather than remove it.

4. Mass loss rate (MLR)#

Mass loss rate is the speed at which the specimen loses mass while it burns, measured continuously by the load cell under the specimen holder, and it shows how fast the plastic is being turned into combustible gas. ASTM E1354-26 lists mass loss rates among its five outputs. Our source set holds no mass loss rate value for any plastic, so the table above leaves that cell empty.

5. Effective heat of combustion (EHC)#

Effective heat of combustion is the heat released per unit of mass lost, calculated by dividing the heat release rate by the mass loss rate, and it shows how completely the gases a plastic gives off actually burn in the flame. A gas-phase flame retardant such as aluminium diethylphosphinate, which releases PO radicals into the flame, can lower the effective heat of combustion because part of the fuel leaves the flame unburnt, and that unburnt fuel leaves the exhaust as smoke. Our source set holds no EHC value for any plastic.

6. Smoke production (SPR, TSP and specific extinction area)#

Smoke production in a cone test is the visible smoke measured by the dimming of a light beam in the exhaust duct while the specimen burns, reported as a smoke production rate, a total smoke production and a specific extinction area per kilogram of mass lost. Phosphinate in polyamide 6 raised total smoke production from 1.31 m2 to 10.1 m2 at 50 kW/m2, about 7.7 times, while cutting the peak. The intumescent polypropylene compounds released 19 to 33 % less smoke than the neat polymers at 35 kW/m2. The oxide residue left by ATH and MDH adsorbs soot, which makes the mineral flame retardants smoke suppressants as well.

7. Char residue#

Char residue is the mass left in the specimen holder when flaming ends, reported as a percentage of the original specimen, and a rising residue is the cone's direct evidence that a flame retardant is working in the condensed phase by building a protective layer. A rising residue is char the flame retardant has built, the protective layer the residue figure weighs. All three neat polypropylenes left less than 1 % at 35 kW/m2, against 14.73 to 18.00 % with the intumescent system, and neat polyamide 6 left 0.6 wt% at 50 kW/m2, against 9.3 wt% with ADP plus the phosphorus, nitrogen and zinc synergist.

8. MARHE and other derived indices#

MARHE, the maximum average rate of heat emission, is a single fire-growth figure calculated from the heat release rate curve rather than measured directly, and it is the cone-derived index that the European railway fire standard EN 45545-2 uses. Rail practice reads it from cone runs at 50 kW/m2. Our source set holds no MARHE limit for any EN 45545-2 hazard level and no MARHE value for a plastic compound, so this page gives neither.

Typical Cone Calorimeter Values of Plastics#

Neat polypropylene reaches a peak heat release rate of 1,148 to 1,332 kW/m2 at 35 kW/m2 depending on whether it is a homopolymer, a random copolymer or a block copolymer, neat polyamide 6 reaches 787.3 kW/m2 at 50 kW/m2, and an unfilled EVA/LLDPE cable compound peaks above 550 kW/m2 at 35 kW/m2. Five neat plastics have flux-matched cone data in our source set.

Rows at different heat fluxes are not comparable with each other. The EVA/LLDPE row comes from a supplier brochure and gives no thickness.

The table has 5 rows and not 20 because a cone value only means something with its heat flux and thickness, and our source set holds flux-matched data for these polymers only; every other polymer is left out rather than filled from a handbook value of unknown flux. Within polypropylene, the three chain architectures spread the neat peak across 184 kW/m2 at one flux and one thickness. Why homopolymer, random and block copolymer polypropylene behave differently is set out in additives for polypropylene.

Polyamide 6 ignites later than polypropylene here, but at a higher flux, so that is no ranking either.

The per-polymer comparison this table leaves out is on flame-retardant plastics and their UL 94 ratings by polymer.

How Do Flame Retardants Change Cone Calorimeter Results? 5 Systems Compared#

The 5 flame retardant systems with sourced cone data on this page are intumescent systems in polypropylene, phosphinates with a P/N synergist in polyamide 6, the mineral flame retardants ATH and MDH in cable compounds, expandable graphite in polyurethane foam, and nanofiller barrier synergists, and the intumescent systems show the largest pHRR reduction in our source set, 78 to 84 % at 35 kW/m2. Each row compares one flame retardant system with its own unfilled polymer at one heat flux.

Percentages are computed from the cited tables and compare each compound with its own unfilled polymer at the same heat flux. Rows 3a and 4 report relative changes only, because the heat flux is not recorded in our source set.

A flame retardant is added to or reacted into a polymer to delay ignition, slow flame spread, reduce heat release or make the material self-extinguishing; it does not make a plastic non-combustible. Mechanisms, loadings and selection for all flame retardants for plastics sit on the family hub.

Our source set holds no flux-matched cone data for brominated systems such as DBDPE or TBBPA with antimony trioxide, so none appears here.

All five systems in the table are halogen-free flame retardants.

1. Intumescent systems in polypropylene#

An intumescent system lowers the peak heat release rate by swelling into a foamed char layer that shields the polymer underneath from the heater, and in polypropylene 25 wt% of a piperazine pyrophosphate, ammonium polyphosphate and charring-agent blend cut the peak from 1,148 to 1,332 kW/m2 to 220 to 255 kW/m2 at 35 kW/m2. The acid, carbon and gas sources of intumescent flame retardants are compared on their own node.

Yin and colleagues (National Engineering Research Center of Flame Retardant Materials, Beijing Institute of Technology, Polymers, 2026) tested three polypropylene architectures with the same blend of 14.2 wt% PAPP, 7.1 wt% ammonium polyphosphate (APP) and 3.7 wt% triazine charring agent, in duplicate on 3 mm plaques. The residue rose from below 1 % to 14.7 to 18.0 %, and time to ignition changed by only 1 to 12 s.

The cone values do not predict the UL 94 rating: the random-copolymer compound failed at 1.6 mm despite a lower peak, while the homopolymer and block copolymer compounds reached V-0. APP-based systems reach V-0 in polypropylene at 22 to 30 wt%, and loadings for each thickness are on flame retardants for polypropylene.

2. Phosphinates and P/N synergists in polyamide 6#

Phosphinates lower the peak heat release rate of polyamide 6 by acting in both phases at once, releasing PO radicals that quench the flame and helping the polymer char, and 15 wt% of aluminium diethylphosphinate cut the peak from 787.3 to 549.0 kW/m2 at 50 kW/m2. Aluminium diethylphosphinate (AlPi or DEPAL, CAS 225789-38-8) works in synergy with melamine polyphosphate. Grades and synergists for phosphinate flame retardants (DEPAL) in PA and PBT are on the node.

Peng and colleagues (Beijing University of Chemical Technology, Polymers, 2026) replaced 3 of the 15 wt% with a phytic acid, benzoguanamine and zinc synergist (PABG@Zn). The peak fell to 362.4 kW/m2, 54 % below neat polyamide 6, and the compound reaches an oxygen index of 30.7 % and UL 94 V-0 at 3.2 mm.

The trade-off the cone shows and a UL 94 bar does not is smoke: total smoke production rose about 7.7 times with ADP alone, the signature of gas-phase flame inhibition. The CAS number and regulatory status of aluminum diethylphosphinate are on its substance page.

3. Mineral flame retardants (ATH and MDH) in cable compounds#

ATH and MDH are the flame retardants that delay ignition in a cone test, by 120 to 160 s in an EVA/LLDPE cable compound at 35 kW/m2, because they absorb heat and release water as they decompose before the polymer can give off enough fuel to ignite. The unfilled compound ignites at about 80 s at the same flux (Huber cable brochure). Coated grades and loadings for mineral flame retardants (ATH and MDH) are compared on the node.

Halogen-free cable compounds carry 160 to 180 phr of mineral, 61.5 wt% at 160 phr, because the effect is physical and grows with the amount of mineral, and the unfilled peak above 550 kW/m2 falls roughly in proportion to the loading.

A synergist can halve the peak again: Alsayed and colleagues (Polymers, 2025) added 10 wt% of a phosphate low-melting glass to a PE-EVA/ATH sheath and measured 142 kW/m2, 52 % below the ATH-only sheath, at a heat flux not recorded in our source set. Aluminium hydroxide releases water from about 200 °C and absorbs 1,051 J/g; the profile of aluminum trihydrate (ATH) is on its substance page.

4. Expandable graphite in polyurethane foam#

Expandable graphite lowers the peak heat release rate by physical intumescence, exfoliating from about 200 °C into an insulating layer of expanded carbon, and in viscoelastic polyurethane foam 15 php of it with 30 php of filler cut the peak by 52 %. Onset temperatures for expandable graphite grades run from 140 to 230 °C, and the black colour limits it to dark parts.

Combined with APP and a reactive phosphorus polyol in a 2025 Polymers study by Węgrzyk and co-authors, expandable graphite cut the peak of viscoelastic foam by 92 %, with an oxygen index of 28 to 31 % and UL 94 V-0. Both results are relative, because the heat flux is not recorded in our source set. The full foam package is on flame retardants for polyurethane foam.

5. Nanofillers and barrier synergists#

Nanofillers such as organoclay, layered double hydroxides and carbon nanotubes lower the heat release of a burning plastic by holding the residue together as a surface barrier, but they seldom pass UL 94 on their own and are used as synergists inside a full flame retardant system. Barrier mechanisms of nanocomposite flame retardants are set out on the node. Replacing 1 wt% of an intumescent system in polypropylene with 1 wt% of layered cerium oxide cut total heat release by 38.9 % and total smoke release by 74.3 % at 35 kW/m2 under ISO 5660-1, and raised the oxygen index from 29.4 to 32.6 vol % O2 (Molecules, 2025).

Why Can a Flame Retardant Lower pHRR but Shorten Time to Ignition?#

A flame retardant can shorten time to ignition because it begins to decompose, and to start the char-forming reactions, at a lower temperature than the plastic it protects, while it lowers the peak heat release rate because that early char and the flame inhibition then hold the burn at a lower intensity. The data in our source set show three patterns.

• Phosphinate in polyamide 6: time to ignition fell from 102 s to 63 s at 50 kW/m2 while the peak fell by 54 %.
• Intumescent system in polypropylene: time to ignition changed by only 1 to 12 s at 35 kW/m2 while the peak fell by 78 to 84 %.
• ATH and MDH in a cable compound: ignition was delayed by 120 to 160 s at 35 kW/m2, the one family in our source set that moves both numbers in the favourable direction.

For selection, a flame retardant judged on the peak alone can hide earlier ignition and higher smoke, so a formulator reads time to ignition, pHRR, total heat release and smoke together, the position Bernhard Schartel (BAM, Berlin) and T. Richard Hull (University of Central Lancashire) take in their 2007 Fire and Materials paper on interpreting cone calorimeter data. Why char and flame inhibition act at different moments is explained under how flame retardants work: gas-phase and condensed-phase action.

Does a lower pHRR mean a better UL 94 rating?#

No: in the same 2026 study, a random-copolymer polypropylene with 25 wt% of an intumescent system had a lower peak heat release rate than the homopolymer compound, 240 against 255 kW/m2 at 35 kW/m2, yet it failed UL 94 at 1.6 mm by burning to the clamp with severe dripping, while the homopolymer compound reached V-0. The cone burns a horizontal plaque under steady radiant heat, while UL 94 applies a small flame to a vertical bar and judges self-extinction and dripping. A compound that drips can lose its rating without any change in heat release, and every rating is valid only at the thickness tested. The afterflame and dripping criteria behind UL 94 flammability ratings explain why the two tests diverge.

Which Specifications Use Heat Release Values?#

Heat release appears in 3 kinds of specification that plastics compounders meet: the European railway standard EN 45545-2, which uses a cone-derived index, the US aircraft cabin rule in 14 CFR Part 25 Appendix F, which uses its own heat release apparatus, and the EU cable classes under EN 13501-6, which measure heat release on a full cable ladder. Only one of the three uses the cone calorimeter.

Heat release values from different apparatus are not interchangeable, even when the units look alike.

Under 14 CFR Part 25, Appendix F, Part IV (current eCFR text), cabin panels, partitions, galley structure and large stowage in airplanes with 20 or more passengers keep the 2-minute total heat release at or below 65 kW·min/m2 and the peak at or below 65 kW/m2, measured in the OSU apparatus. The cable B2ca limit of 30 kW comes from a 20.5 kW burner on a cable ladder. Neither compares with a cone pHRR in kW/m2, and only the rail standard draws on cone data. Rail and aircraft packages that meet these limits are on flame retardants for transportation.

What a Cone Calorimeter Cannot Tell You#

A cone calorimeter cannot tell you on its own whether a part is safe in a real fire, and ASTM E1354-26 says so itself: the method "does not by itself incorporate all factors required for fire hazard or fire risk assessment". Five questions need a different test.

• Self-extinction and dripping of a vertical bar: judged by UL 94 at a stated thickness.
• Oxygen demand of a material: ranked by the limiting oxygen index.
• Smoke density in a closed chamber: measured by ISO 5659-2 or ASTM E662, not by the cone's dynamic smoke channel.
• Ignition by an overheated electrical part: tested by the glow wire methods of IEC 60695-2.
• Behaviour of a full cable bundle or an installed product: tested at large scale, for cables by EN 50399.

The cone also does not apply to end-use products without planar or nearly planar surfaces (ASTM E1354-26, section 5.3), so a moulded part with ribs and bosses is tested as a flat plaque of the same compound.

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Which Other Fire Tests Are Run Alongside the Cone Calorimeter?#

A flame-retarded compound is usually tested by four groups of methods besides the cone calorimeter: the limiting oxygen index and UL 94 for ranking and classification, smoke chambers and cable tests for smoke and large-scale behaviour, microscale combustion calorimetry for milligram screening, and the glow wire for electrical ignition. All 42 methods are mapped on testing plastic additives and additive-dependent properties.

Limiting oxygen index and UL 94#

The limiting oxygen index ranks how much oxygen a plastic needs to keep burning, from 17.5 to 17.8 vol % O2 for neat polypropylene to 29 to 33 vol % O2 with an intumescent system, while UL 94 classifies whether a bar self-extinguishes and drips at a stated thickness. The index is measured under ASTM D2863-23e1 and ISO 4589-2, and how 11 flame retardant systems raise it is on limiting oxygen index (LOI).

Smoke density and cable fire tests#

Smoke density chambers measure the specific optical density of smoke in a closed box under ISO 5659-2 or ASTM E662, a different number from the cone's dynamic smoke production, and the EU cable classes are decided on a full cable ladder under EN 50399, where heat release is reported in kW, not kW/m2. Chamber methods and limits, including IEC 61034 for cables, are on smoke density testing.

EN 50399 measures flame spread, total heat release, peak heat release rate, FIGRA and smoke for the CPR classes Aca to Fca. FIGRA and the Euroclass limits are on cable fire tests and CPR classes.

Which flame retardant systems reach B2ca is set out in flame retardants for wire and cable.

Microscale combustion calorimetry for milligram screening#

Microscale combustion calorimetry measures heat release from milligram specimens heated at 0.2 to 2 K/s under ASTM D7309-26a, using the same oxygen-consumption principle as the cone, which makes it a screening step before a formulation is moulded into 100 x 100 mm plaques.

Glow wire and electrical fire tests#

The glow wire test asks a different question from the cone, whether a hot electrical contact can ignite the part, and household appliances under IEC 60335-1 need a GWFI of at least 850 °C and a GWIT of at least 775 °C. Both indices use a 30 s application and are measured as described under glow wire test (GWFI, GWIT).

Where can you get cone calorimeter testing, and what does it cost?#

Cone calorimeter testing is bought from independent fire laboratories and from the fire labs of flame retardant suppliers, and the price depends on the number of specimens, heat fluxes and replicates, so this page quotes no figure. A test order should name the heat flux and the thickness, because a result without them cannot be compared. Five items belong in the order.

• Standard and edition: ISO 5660-1:2015 or ASTM E1354-26.
• Heat flux: 35 or 50 kW/m2, the same for every specimen to be compared.
• Specimen: 100 x 100 mm plaques at the thickness of the end part.
• Replicates: at least two per formulation, as published studies run.
• Outputs: TTI, the full HRR curve, pHRR, THR, smoke and residue, not pHRR alone.

Before ordering a cone test by polymer, the flame retardant selector by polymer and UL 94 rating narrows the systems worth testing.

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