Flame Retardants for Plastics: 13 Types, Mechanisms, Dosage and Selection

Flame retardants for plastics are additives that delay ignition and slow flame spread in a polymer, and they make up 2 to 28 wt% of the finished product; this reference sorts them into 13 chemical types, from aluminium trihydrate to phosphinates. They account for 13 % of all plastic additives by weight, the third-largest family after plasticizers at 34 % and fillers at 28 %, so which flame retardant goes into which plastic, and at what loading?

Flame retardant additives interrupt the combustion cycle of a burning polymer in the gas phase, in the condensed phase, or in both at once. The 13 chemical types are mineral flame retardants, brominated flame retardants, polymeric brominated flame retardants, chlorinated flame retardants, antimony and other synergists, inorganic phosphorus flame retardants, organophosphates and phosphonates, phosphinates and DOPO, nitrogen-based flame retardants, intumescent systems, smoke suppressants, sulfonate salts for polycarbonate, and nanocomposites. Fire-retardant sprays, paints and textile finishes are outside the scope of this page.

Flame retardants are the third-largest family of plastic additives by weight, and this page follows one chain from chemistry to purchase order: how each type breaks the fire, which type suits each polymer and application, how much is needed to reach UL 94 V-0, the 8 selection steps, the fire tests, the EU and US rules, the producers, and all 56 flame retardant substances covered on this site. The European Chemicals Agency lists 39 substances under the flame retardant function in its plastic additives mapping of chemicals registered above 100 t/yr.

Table T1. The 13 flame retardant types at a glance.

Group header = chemical family; many commercial systems combine 2 or 3 types, for example AlPi with MPP, or DBDPE with Sb2O3.

What Is a Flame Retardant?#

A flame retardant is a substance added to or reacted into a plastic to delay its ignition, slow flame spread and lower heat release, so that the part passes a defined fire test such as UL 94 V-0 at a stated thickness. Global consumption passed 2 million tonnes in 2013, and the additive is bought against a test result rather than against a chemical specification.

No flame retardant makes a plastic fireproof. Every commercial system aims at one named class, such as UL 94 V-0 at 0.8 mm, a limiting oxygen index above 26 vol % O2 in a PVC cable sheath, or a euroclass under the EU Construction Products Regulation. How much difference does that make in a real fire? In room-scale tests run by the US National Bureau of Standards in 1988, flame-retarded products gave more than 15 times the available escape time and released one quarter of the heat of the untreated products.

The term fire retardant is used as a trade synonym, most often for wood, textiles and sprays, while flame retardant dominates in plastics compounding and in the additive trade.

What are flame retardants used for in plastics?#

Flame retardants are used in plastics wherever a fire standard applies: cable insulation, electrical housings and connectors, building insulation foams, vehicle and rail interiors, and printed circuit boards. The 6 volume applications and their reference systems are listed below.

• Wire and cable compounds: halogen-free EVA and LLDPE jackets carry 160 to 180 phr of ATH or MDH, and full recipes are in additives for wire and cable compounds.
• Electrical and electronic housings and connectors: glass-filled polyamide with aluminium diethylphosphinate reaches UL 94 V-0 from 0.4 to 3.2 mm, and HIPS housings use DBDPE with antimony trioxide.
• PC/ABS housings for IT equipment: aryl oligophosphates such as BDP and RDP replace halogen chemistry, with PTFE as the anti-drip agent.
• Building insulation foams: EPS and XPS boards use the polymeric PolyFR, while rigid polyurethane insulation uses TCPP and expandable graphite.
• Transport interiors: rail parts are qualified to EN 45545-2 hazard levels, vehicle interiors to FMVSS 302 at no more than 102 mm/min.
• Printed circuit boards: FR-4 epoxy laminates carry TBBPA reacted into the resin, and halogen-free laminates use DOPO chemistry.

Additive, reactive and polymeric flame retardants#

Flame retardants enter a plastic in 3 ways: additive flame retardants such as ATH and DBDPE are blended into the melt, reactive flame retardants such as TBBPA in FR-4 epoxy are built into the polymer chain, and polymeric flame retardants such as brominated polystyrene are high-molecular-weight additives that do not bloom. The difference decides migration behaviour, and therefore decides which regulatory instruments touch the product.

A reactive flame retardant built into the backbone is not free to migrate, which is why TBBPA in a cured FR-4 laminate behaves differently from TBBPA blended into ABS. DOPO is the same kind of reactive building block in epoxy resins, and CEPPA is a reactive phosphorus comonomer in PET fibre and film. Polymeric brominated grades occupy a third position: their high molecular weight prevents blooming and limits bioavailability, and they sit outside the scope of the EU restriction now being prepared for non-polymeric aromatic brominated flame retardants. The definitions are compared on reactive vs additive flame retardants.

Table T2. Additive, reactive and polymeric flame retardants.

Halogenated vs halogen-free flame retardants#

Halogenated flame retardants contain bromine or chlorine and act mainly in the flame, while halogen-free flame retardants such as ATH, phosphinates and melamine derivatives act by cooling, charring or dilution and release no acidic halogen gases. The choice is rarely a pure performance decision, because 2 regulations and one cable class have already made it for large parts of the market.

The 2 cases are set out below.

• Halogenated, when the loading has to stay low and the part is thin. A HIPS television housing reaches UL 94 V-0 at 0.8 mm with about 8 to 12 wt% DBDPE plus 5 wt% antimony trioxide.
• Halogen-free, when the class or the product law requires it. A cable class with an acidity rating of a1 needs a conductivity below 2.5 microsiemens per millimetre and a pH above 4.3 under EN 60754-2, which only a halogen-free compound meets; Ecodesign Regulation (EU) 2019/2021 has banned halogenated flame retardants in electronic display enclosures and stands since 1 March 2021, and New York has done the same since 1 January 2024.

Low-smoke halogen-free cable compounds appear under 7 trade acronyms, LSZH, LSF, LS0H, LSOH, HFFR, ZHFR and NHFR, and every HFFR system is compared on halogen-free flame retardants.

Is a flame retardant the same as a fire retardant or a flame-resistant material?#

Yes and no: fire retardant is used as a synonym for flame retardant, while a flame-resistant plastic reaches its fire class by its own chemistry, without an added flame retardant. Unmodified polycarbonate is the clearest flame-resistant example, rating UL 94 HB to V-2 with a limiting oxygen index of 25 to 29 vol % O2. Polyolefins and styrenics are not flame resistant in that sense, because polypropylene has a limiting oxygen index of about 17.5 vol % O2 and burns in air, so it reaches a vertical class only with an added flame retardant.

How Do Flame Retardants Work?#

Flame retardants work by breaking the combustion cycle of a burning polymer at one or more points: they trap flame radicals in the gas phase, cool and dilute the fuel, or build a char or glassy barrier on the surface. Bromine, chlorine and phosphorus species act mainly in the flame, mineral hydroxides and carbonates act mainly in the solid, and intumescent systems build a physical barrier between the two.

Most commercial packages attack more than one point, which is why the loading needed for a rating cannot be read off a single mechanism. Bernhard Schartel at the German Federal Institute for Materials Research and Testing (BAM) grouped phosphorus action into condensed-phase modes (charring, intumescence and inorganic glass formation) and a gas-phase mode (flame inhibition) in a 2010 review in Materials, and the same substance can switch between them depending on the host polymer. The chemistry step by step is on how flame retardants work.

The polymer combustion cycle#

A polymer burns in a 5-step cycle: heat breaks it into flammable gases, the gases mix with air, they ignite, the flame releases heat, and that heat feeds back to the surface to break down more polymer. Each step is a place to intervene, and each flame retardant type is defined by the step it attacks.

1. Heating: an external heat flux raises the surface temperature of the polymer.
2. Pyrolysis: the polymer decomposes into volatile fragments, which are the fuel.
3. Mixing: the volatiles diffuse into the air above the surface.
4. Ignition and flame: the mixture ignites and a flame front establishes itself.
5. Heat feedback: part of the flame's heat returns to the surface and drives further pyrolysis.

Cone calorimetry measures that feedback loop as peak heat release rate. Unfilled EVA and LLDPE cable compound peaks above 550 kW/m2 at an external flux of 35 kW/m2, and adding ATH or MDH delays ignition by 120 to 160 s (Huber). Neat polypropylene reaches 1,148 to 1,332 kW/m2 at 35 kW/m2, while an intumescent polypropylene compound at the same flux stays at 220 to 255 kW/m2.

Gas-phase action: radical trapping and dilution#

In the gas phase, bromine, chlorine and phosphorus species trap the H and OH radicals that carry the flame reaction, while water, carbon dioxide and ammonia released by minerals and ammonium polyphosphate dilute the fuel and the oxygen. The 2 gas-phase routes differ in chemistry and in the loading each one needs.

• Radical trapping: hydrogen bromide, hydrogen chloride and, in antimony-containing systems, the volatile antimony trihalide SbX3 scavenge H and OH radicals and replace them with the far less reactive halogen radical X. Aluminium diethylphosphinate releases PO radicals that act on the same radical pool, which is why a phosphinate works in the flame as well as in the char.
• Dilution: ATH and MDH release water, huntite-hydromagnesite releases water and then carbon dioxide, and ammonium polyphosphate releases ammonia. These gases are inert, so they cut the fuel and the oxygen concentration in the flame zone at once.

Flame inhibition carries a cost that is easy to miss on a pass or fail test sheet. Bernhard Schartel at the German Federal Institute for Materials Research and Testing (BAM) showed in a 2010 review in Materials that flame inhibition lowers combustion efficiency and therefore raises the carbon monoxide yield, so a compound that improves on UL 94 can worsen on toxic gas emission.

Condensed-phase action: cooling, charring and barrier layers#

In the condensed phase, flame retardants cool the polymer by endothermic decomposition, as aluminium trihydrate does when it absorbs 1051 J/g from about 200 °C, or they turn the surface into an insulating char or glassy layer. The decomposition onset is the single most important number in the table below, because it has to sit above the compounding and moulding temperature and below the pyrolysis temperature of the polymer.

Char formation is the second route. Ammonium polyphosphate and red phosphorus form phosphoric and polyphosphoric acids that dehydrate the polymer into a carbon-rich residue, and aryl phosphates such as BDP enhance the natural charring of polycarbonate. Zinc borate adds a third route by forming a borate glass over the residue, and aluminium diethylphosphinate leaves an aluminium phosphate barrier. That carbon-rich residue, called char, carries the insulation, so a flame retardant leaving no residue has to work entirely in the flame.

Table T2b. Thermal data of condensed-phase flame retardants.

Synergy and antagonism in flame-retardant systems#

Flame retardants are rarely used alone: antimony trioxide multiplies the effect of bromine donors, melamine polyphosphate boosts aluminium diethylphosphinate, and PTFE stops flaming drips, while the same flame retardants can weaken antioxidants and hindered amine light stabilizers. A formulation that gains a fire class can lose its service life, so both directions have to be checked. The 5 synergy pairs with published numbers are listed below.

• Antimony trioxide with a bromine donor: Sb2O3 has little effect alone, but with hydrogen halide it forms SbOX and then volatile SbX3; 10.7 wt% bromine plus 5 wt% Sb2O3 gives HIPS UL 94 V-0 at 0.8 mm (Albemarle).
• Melamine polyphosphate with aluminium diethylphosphinate: the standard halogen-free package for glass-filled polyamide, sold as the Exolit OP 1312 blend.
• Zinc borate with magnesium hydroxide: 10 wt% zinc borate plus 10 wt% MDH raised the limiting oxygen index of a PP/CaCO3 composite to 29.4 vol % O2 in a 2024 study in Materials.
• Piperazine pyrophosphate with melamine polyphosphate: a 2:1 ratio at 21 wt% total gives UL 94 V-0 in virgin and recycled polypropylene.
• Metal oxides in intumescent PP: 0.25 wt% of ZnO or MnO can raise the limiting oxygen index of an APP system to 30 vol % O2 and deliver V-0 in a 2025 study in Polymers.

Antagonism is the shorter list and the more expensive one to discover late. The 4 recorded interactions are listed below.

• Flame retardants and antioxidants: flame retardants reduce the effectiveness of antioxidants.
• Halogenated flame retardants and antistats: amine and amide antistats react with halogenated flame retardants.
• Acidic flame retardants and hindered amine light stabilizers: basic N-H HALS interact with acidic species, including halogenated flame retardants.
• AlPi with melamine polyphosphate in PA66: the compound can bloom as a white frost after ageing at 85 °C and 85 % relative humidity.

A full matrix is on additive interactions: synergy and antagonism.

13 Types of Flame Retardants by Chemistry#

The 13 types of flame retardants used in plastics are mineral hydroxides, brominated flame retardants, polymeric brominated flame retardants, chlorinated flame retardants, antimony and other synergists, inorganic phosphorus flame retardants, organophosphates and phosphonates, phosphinates and DOPO, nitrogen-based flame retardants, intumescent systems, smoke suppressants, sulfonate salts and nanocomposites. Examples include aluminium trihydrate (ATH), decabromodiphenyl ethane (DBDPE), antimony trioxide, ammonium polyphosphate, triphenyl phosphate and melamine cyanurate.

The order follows chemistry rather than market share, and it is the same order used in Table T1, in the complete substance list and in the class diagram below.

1. Mineral flame retardants (ATH, MDH, boehmite, huntite)#

Mineral flame retardants are metal hydroxides and hydroxycarbonates, such as aluminium trihydrate (ATH) and magnesium hydroxide (MDH), that absorb heat and release water, and they need 160 to 180 phr in halogen-free cable compounds. ATH releases water from about 200 °C, absorbs 1051 J/g and has a theoretical loss on ignition of 34.6 %, while MDH stays stable to about 320 °C, absorbs 1316 J/g and loses 31.0 %, a processing window about 110 °C higher than ATH (Huber). Huntite-hydromagnesite releases water from about 220 °C and carbon dioxide from about 330 °C (LKAB Minerals), and boehmite is the higher-temperature oxide hydroxide used where ATH decomposes too early, as in epoxy circuit board laminates.

Loadings are extreme by additive standards. A halogen-free EVA and LLDPE cable compound carries 160 phr of ATH, equal to 61.5 wt%, and Huber cites MDH filling levels up to 65 wt% in polypropylene, with a supplier claim of more than 65 wt% for coated grades. ATH and MDH delay ignition of unfilled EVA and LLDPE by 120 to 160 s at an external flux of 35 kW/m2, and the alumina or magnesia residue also suppresses smoke. Neither mineral is on the REACH Candidate List, and aluminum hydroxide has no harmonised CLP entry. Grades are compared on mineral flame retardants.

2. Brominated flame retardants#

Brominated flame retardants are organic bromine compounds, such as DBDPE, TBBPA and EBTBP, that release hydrogen bromide in a fire and, with antimony trioxide, give styrenics and engineering plastics UL 94 V-0 at low loadings. Sales reached 390,000 t in 2011, about 19.7 % of the flame retardant market.

DBDPE (Saytex 8010) contains at least 82 % bromine and melts above 345 °C; in HIPS, 10.7 wt% bromine with 5 wt% antimony trioxide gives UL 94 V-0 at 0.8 mm, which corresponds to about 8 to 12 wt% DBDPE. TBBPA is the reactive flame retardant of FR-4 epoxy laminates and an additive flame retardant in ABS. EBTBP (Saytex BT-93) is UV-stable and does not bloom, which suits coloured HIPS and polycarbonate housings, and FR-370 gives polypropylene a UL 94 V-2 class. The legacy members, decaBDE and HBCD, are now persistent organic pollutants, and DBDPE joined the REACH Candidate List on 5 November 2025 as a vPvB substance but is not restricted. Every brominated substance and its status is on brominated flame retardants.

3. Polymeric brominated flame retardants#

Polymeric brominated flame retardants are high-molecular-weight bromine carriers, such as brominated polystyrene and PolyFR, that do not bloom and fall outside the EU's planned restriction of non-polymeric aromatic brominated flame retardants. Their high molecular weight prevents blooming and limits bioavailability, which is the property that separates them from the additive brominated flame retardants above.

Brominated polystyrene (Saytex HP-3010 and HP-7010) is the thermally stable choice for glass-filled PA66 and PBT, used with antimony trioxide or zinc stannate. PolyFR, a brominated butadiene-styrene block copolymer with about 65 % bromine, replaced HBCD in EPS and XPS building insulation and is sold as Emerald Innovation 3000, FR-122P and GreenCrest. Poly(pentabromobenzyl acrylate), with about 71 % bromine, serves glass-filled polyamide and PBT connectors where comparative tracking index and recyclability matter, and brominated epoxy oligomers serve PBT, ABS and HIPS. The class is compared on polymeric flame retardants.

4. Chlorinated flame retardants#

Chlorinated flame retardants are organochlorine compounds, such as Dechlorane Plus and the chlorinated paraffins, that release hydrogen chloride to trap flame radicals, and 3 of them are now listed as persistent organic pollutants under the Stockholm Convention. Chlorinated paraffins are split by chain length into SCCP at C10 to C13, MCCP at C14 to C17 and LCCP above C17, carry roughly 30 to 70 wt% chlorine, and act as secondary plasticizer and flame retardant at once, normally with antimony trioxide; their dual role is covered on chlorinated paraffins.

Dechlorane Plus is a chlorinated cycloaliphatic flame retardant for nylon, wire and cable and polypropylene, melting at 350 °C. It has been on the REACH Candidate List since 15 January 2018 as vPvB, was listed in Stockholm Annex A at COP-11 in 2023, and was added to Annex I of the EU POPs Regulation by Delegated Regulation (EU) 2025/1930, in force since 15 October 2025, at 1,000 mg/kg until 15 April 2028 and 1 mg/kg after that. SCCP has been a Stockholm POP since 2017 and MCCP since COP-12 in 2025. The chlorinated phosphate esters TCEP, TCPP, TDCPP and V6 belong chemically to type 7 below, and the class is covered on chlorinated flame retardants.

5. Antimony and other flame retardant synergists#

Flame retardant synergists, led by antimony trioxide, add little fire protection alone but multiply the effect of halogen donors, and zinc borate, zinc stannate and PTFE anti-drip agents complete most commercial packages. Antimony trioxide (CAS 1309-64-4) reacts with hydrogen halide to form SbOX and then the volatile SbX3 that carries radical inhibition into the flame.

Use levels are low compared with the halogen donor: 5 wt% Sb2O3 with 10.7 wt% bromine in HIPS, and 5 phr Sb2O3 with 50 phr ATH in a flexible PVC cable compound (Huber). Colloidal antimony pentoxide serves fibres and films where particle size controls light scattering, and sodium antimonate is preferred in polyesters because it is less catalytically active towards depolymerisation. Zinc borate at 3 to 6 phr with ATH cuts smoke and dripping in PVC, while zinc stannate and zinc hydroxystannate replace antimony trioxide. PTFE is the standard anti-drip agent, at 0.1 phr in published examples and 0.4 wt% in a 2024 PC/ABS study. Antimony trioxide carries a harmonised Carc. 2 H351 classification, was listed under California Proposition 65 for cancer on 1 October 1990 and was evaluated by IARC as Group 2A in 2022, but it is not on the REACH Candidate List. Replacements are compared on flame retardant synergists.

6. Inorganic phosphorus flame retardants (red phosphorus, APP, hypophosphites)#

Inorganic phosphorus flame retardants, such as red phosphorus, ammonium polyphosphate (APP) and aluminium hypophosphite, form phosphoric acids in a fire that turn the polymer surface into char. They are halogen-free, they work in the condensed phase, and their decomposition onset sets the polymer they can be used in.

Red phosphorus reaches UL 94 V-0 in glass-filled PA66 by carbonaceous charring, as Bernhard Schartel described in his 2010 review in Materials, and it is supplied encapsulated or as a masterbatch because it is classified Flam. Sol. 1 H228; its dark colour restricts its use. APP phase II starts to decompose at about 240 °C, releases ammonia and polyphosphoric acid, and is the acid source of intumescent polypropylene at 22 to 30 wt% for UL 94 V-0, with processing up to about 220 °C. Aluminium hypophosphite serves PBT, polyamide and polystyrene, and calcium hypophosphite is listed by ECHA at 1 wt% in polyolefins. The class is covered on phosphorus flame retardants.

7. Organophosphate and phosphonate flame retardants#

Organophosphate flame retardants are phosphate esters, such as triphenyl phosphate, RDP, BDP and TCPP, that act mainly in the gas phase and also plasticise, which is why they suit PC/ABS blends and polyurethane foam. That side effect is the reason their loadings show up in heat deflection temperature data as well as in fire data.

Triphenyl phosphate is both flame retardant and plasticizer in PC/ABS, PPE/HIPS and PVC, and has been on the REACH Candidate List since 7 November 2024 for endocrine disrupting properties in the environment. Schartel showed that the aryl oligophosphate BDP works mainly through gas-phase flame inhibition in polycarbonate alone but also enhances polycarbonate charring in PC/ABS. In a 2024 study, 20 wt% of an aryl bisphosphate with 0.4 wt% PTFE gave PC/ABS UL 94 V-0 with a limiting oxygen index of 25.4 vol % O2 and a heat deflection temperature of 72.6 °C. The chlorinated phosphates are the foam branch: TCPP (Fyrol PCF, Levagard PP) is the workhorse of rigid and flexible polyurethane foam, TDCPP serves flexible foam, and TCEP is legacy. The phosphonates DMMP and DMPP go into rigid polyurethane and unsaturated polyester, with DMPP listed by ECHA at 15 wt% in PUR. Grades and status are on organophosphate flame retardants.

8. Phosphinate and DOPO flame retardants#

Phosphinate flame retardants, led by aluminium diethylphosphinate (AlPi, DEPAL), survive processing above 300 °C and give glass-filled polyamide UL 94 V-0 at 15 to 20 wt%, while DOPO does the same job reactively in epoxy laminates. AlPi (CAS 225789-38-8) carries 23.3 to 24.0 wt% phosphorus and decomposes above 300 °C, which is what lets it pass through polyamide and polyester melts that destroy ATH and most APP.

The published loadings are consistent across grades. About 15 wt% of Exolit OP 1230 gives PA 6T/66 UL 94 V-0 at 1.6 mm and 0.8 mm; 15 to 20 wt% of the Exolit OP 1312 blend gives glass-filled PA6 and PA66 V-0 from 0.4 to 3.2 mm with a glow-wire ignition temperature of 775 °C, a glow-wire flammability index of 960 °C and a comparative tracking index of 600 V; and 18 wt% of Exolit OP 1260 gives glass-filled PBT V-0 (Clariant). Thermoplastic elastomers need 20 to 40 wt% with synergists. DOPO is the reactive alternative, reaching V-0 in epoxy research formulations at about 1 to 1.2 wt% phosphorus. Grades by polymer are on phosphinate flame retardants.

9. Nitrogen-based flame retardants#

Nitrogen-based flame retardants are melamine and its salts, such as melamine cyanurate and melamine polyphosphate, that decompose endothermically, release inert gases and act as synergists for phosphorus flame retardants. They are halogen-free, and 2 of the 4 commercial members work only in combination.

Melamine cyanurate is the exception, reaching UL 94 V-0 in unfilled PA6 and PA66 as the sole additive by promoting melt flow and dripping away from the flame; its dosage is not established in this reference. Melamine polyphosphate is the standard synergist with aluminium diethylphosphinate in glass-filled polyamide and with piperazine pyrophosphate in polypropylene, and melamine pyrophosphate is a further nitrogen-phosphorus char former. Melamine itself is the gas source in intumescent systems and a flame retardant in flexible polyurethane foam; it has been on the REACH Candidate List since 17 January 2023 under Article 57(f), carries a harmonised Carc. 2 H351 classification, and is authorised in food contact as FCM No 239 with a specific migration limit of 2.5 mg/kg. The class is covered on nitrogen-based flame retardants.

10. Intumescent flame retardants and expandable graphite#

Intumescent flame retardants swell into an insulating carbon foam when heated, either chemically, from an acid source with a carbon source and a blowing agent, or physically, as expandable graphite does from about 200 °C. A chemical intumescent needs all 3 components: ammonium polyphosphate as the acid source, pentaerythritol as the carbon source and melamine as the blowing agent.

In polypropylene the formulated APP systems Exolit AP 750 and AP 766 reach UL 94 V-0 at 22 to 30 wt%, and a piperazine pyrophosphate to melamine polyphosphate blend at 2:1 reaches V-0 at 21 wt% total, including in recycled polypropylene. Expandable graphite works by physics rather than acid chemistry: the intercalant decomposes and the gas pressure exfoliates the flakes into insulating carbon worms, with an onset of about 200 °C in a range of 140 to 230 °C and a processing ceiling below about 230 °C. Its main use is polyurethane foam, where 15 php with 30 php of filler cut the peak heat release rate of a viscoelastic foam by 52 % in a 2024 study, and expandable graphite with APP and a phosphorus polyol reached a limiting oxygen index of 28 to 31 vol % O2, V-0 and a 92 % cut in peak heat release rate. The class is covered on intumescent flame retardants.

11. Smoke suppressants#

Smoke suppressants are molybdates, tin compounds and borates, such as ammonium octamolybdate and zinc hydroxystannate, that cut the smoke from PVC and other halogenated plastics at 3 to 5 phr. Smoke matters because the EU cable classes rate it separately from heat release, and because aircraft interiors are held to a specific optical density of no more than 200 at 4 minutes.

Ammonium octamolybdate and molybdenum trioxide are the molybdate route in PVC; molybdenum trioxide carries a harmonised Carc. 2 H351 classification and was listed under California Proposition 65 for cancer on 19 March 2021. Zinc hydroxystannate at 3 to 5 phr cut total smoke production by about 46 to 53 % in PVC research formulations, and zinc borate suppresses afterglow and smoke while promoting char. The class is covered on smoke suppressants.

12. Sulfonate salts for polycarbonate#

Sulfonate salts are ultra-low-dose flame retardants for transparent polycarbonate, either the fluorinated PFBS-K (Rimar salt) or the fluorine-free KSS, that catalyse polycarbonate charring without clouding the part. They migrate to the surface and trigger crosslinking and charring of the polycarbonate itself, which lifts unmodified polycarbonate, rated UL 94 HB to V-2, to a vertical class without a bulk filler.

PFBS-K (CAS 29420-49-3, Bayowet C4) is the commercial workhorse for transparent polycarbonate, but it is a PFAS, has been on the REACH Candidate List since 16 January 2020 under the PFBS and salts entry, and falls within the scope of the proposed EU universal PFAS restriction, which is pending. KSS (CAS 63316-43-8) is the fluorine-free alternative and is not on the Candidate List. Polycarbonate systems are compared on flame retardants for polycarbonate.

13. Nanocomposite flame retardants#

Nanocomposite flame retardants are platelet or tube-shaped nanofillers, such as organoclay (montmorillonite), layered double hydroxides and carbon nanotubes, that slow burning by forming a surface barrier and are used as synergists. They lower the peak heat release rate by holding a residue layer together rather than by releasing water or trapping radicals, so they are combined with a conventional flame retardant.

The one published system in this reference shows the pattern: a 25 % glass-filled PA6 with expandable graphite, aluminium diethylphosphinate, melamine polyphosphate and montmorillonite at 20 wt% total reached UL 94 V-0, a limiting oxygen index of 32 vol % O2 and a peak heat release rate of 103 kW/m2 in a 2023 study in Polymers. Stand-alone nanofiller loadings are not established in this reference. The class is covered on nanocomposite flame retardants.

Which Flame Retardant Suits Each Polymer?#

Each polymer takes the flame retardant that survives its processing temperature and matches how it burns: ATH suits EVA and PVC below 200 °C, phosphinates suit glass-filled polyamide at 240 to 320 °C, intumescent APP suits polypropylene, and bromine-antimony systems suit HIPS and ABS. Engineering polymers process at roughly 240 to 320 °C, which excludes ATH and most APP, and that constraint removes more candidates than any regulation.

The second constraint is how the polymer burns. Polypropylene has a limiting oxygen index of about 17.5 vol % O2 and drips, so it needs a char former and, in thin sections, an anti-drip agent; polycarbonate already chars and reaches UL 94 HB to V-2 unmodified with a limiting oxygen index of 25 to 29 vol % O2, so it needs only a charring catalyst; PVC supplies its own chlorine, so it needs a synergist rather than a halogen donor. Glass fibre changes the answer again, because the fibres wick the flame along the specimen, which is why unfilled PA6 and PA66 can be rated with melamine cyanurate alone while glass-filled grades need 15 to 20 wt% of a phosphinate blend.

The third constraint is the property the flame retardant costs. Aryl phosphates plasticise, so 20 wt% in PC/ABS pulls the heat deflection temperature to 72.6 °C; mineral hydroxides at 160 phr turn the compound into a filled system; red phosphorus colours the part and raises corrosion concerns for some electrical equipment makers.

Table T3. Flame retardant systems by polymer.

Is polypropylene flame retardant?#

No: polypropylene burns readily, with a limiting oxygen index of only about 17.5 vol % O2, and it reaches UL 94 V-0 only with about 21 to 30 wt% of an intumescent phosphorus system. The commercial routes are an APP-based intumescent at 22 to 30 wt% or a piperazine pyrophosphate and melamine polyphosphate blend at 21 wt%. A lower class is cheaper to buy: the brominated phosphate FR-370 gives polypropylene UL 94 V-2 at melt-blendable loadings, which is the class required for moulded parts and fibres that are not covered by a vertical specification.

Which plastics are flame retardant without additives?#

Few plastics resist fire on their own: polycarbonate reaches UL 94 V-2 unmodified with a limiting oxygen index of 25 to 29 vol % O2, while polyolefins and styrenics burn and need a flame retardant. PVC is the second case, because the base polymer is 57 % chlorine by mass and therefore supplies its own halogen donor, although flexible PVC cable still needs ATH and a synergist to reach 26 to 27 vol % O2 and UL 94 V-0 at 3 mm. PA6 sits at the boundary at 21.0 vol % O2, level with air. Every polymer's rating is on flame-retardant plastics: UL 94 ratings by polymer.

Which Flame Retardant Suits Each Application?#

The application sets the fire standard, and the standard sets the flame retardant: EU cable classes with an a1 acidity rating need halogen-free ATH or MDH compounds, appliance parts need glow-wire and UL 94 V-0 performance, and rail parts need EN 45545-2 hazard levels. The standard normally arrives before the polymer is chosen.

Wire and cable is the most prescriptive case. Under EN 13501-6 a cable carries a reaction-to-fire class from Aca to Fca plus separate ratings for smoke, flaming droplets and acidity, and the acidity rating a1, defined in EN 60754-2 as a conductivity below 2.5 microsiemens per millimetre with a pH above 4.3, can only be met by a halogen-free compound. That is what pushes a cable jacket to 160 to 180 phr of ATH or MDH. The new Construction Products Regulation (EU) 2024/3110 applies from 8 January 2026, with cables as product family 31.

Electrical and electronic equipment is driven by 3 numbers rather than by a class letter. IEC 60335-1 clause 30.2.3 requires a glow-wire flammability index of at least 850 °C and a glow-wire ignition temperature of at least 775 °C, or a test on the part at 750 °C with flaming of no more than 2 s, and connector specifications add a comparative tracking index up to 600 V and UL 94 V-0 at 0.4 to 1.6 mm. Halogen chemistry is closed off in one segment, because Ecodesign Regulation (EU) 2019/2021 has banned halogenated flame retardants in electronic display enclosures and stands since 1 March 2021.

Transport splits by mode: FMVSS 302 under 49 CFR 571.302 holds vehicle interiors to a horizontal burn rate of no more than 102 mm/min on a 102 by 356 mm specimen; EN 45545-2 sets rail hazard levels, where glass-filled PA66 with an Exolit OP phosphinate reaches R22 HL3 and glass-filled PBT reaches R22 HL2; and 14 CFR 25 Appendix F Part IV caps aircraft interiors at a 2-minute heat release of 65 kW·min/m2 with a peak of 65 kW/m2. Building and construction takes the fourth route: EPS insulation has to be lifted from a limiting oxygen index of about 18 vol % O2 to the ASTM C578 requirement above 24 vol % O2, normally with PolyFR, and rigid polyurethane insulation uses TCPP and expandable graphite. Furniture foam in California follows TB 117-2013, whose smoulder test on the cover fabric replaced the open-flame foam test from 2014.

Table T4. Flame retardant systems by application.

Electrical and electronic parts rarely carry a flame retardant alone, because the same housing also needs impact modifiers, heat stabilizers and colour, and the full package is on additives for electrical and electronics.

How Much Flame Retardant Is Needed? Loadings for UL 94 V-0#

Flame retardants make up 2 to 28 wt% of most finished plastics, from under 1 wt% of a synergist to about 15 to 20 wt% of a phosphinate in glass-filled polyamide, while halogen-free cable compounds carry 160 to 180 phr, about 60 wt%, of mineral hydroxide. The 2 to 28 wt% range comes from Chea and colleagues in 2025, after Hahladakis and colleagues in 2018, and describes finished plastic products across all applications; the cable figure describes one extreme filled compound, so the 2 numbers use different bases.

Units decide whether a number is comparable at all. Loadings are quoted in wt% of the compound for thermoplastics, in phr, meaning parts per hundred parts of resin, for PVC and cable compounds, in php, meaning parts per hundred parts of polyol, for polyurethane foam, and in wt% phosphorus for reactive epoxy systems. A phr value converts to wt% as the part's phr divided by the total phr, multiplied by 100, so 160 phr of ATH in the Huber halogen-free reference is 61.5 wt%; convert cable loadings with PHR (parts per hundred resin).

Every UL 94 rating in the table carries its specimen thickness, because the same compound can rate V-0 at 3.2 mm and V-2 at 0.8 mm. Where a loading is not established in this reference, no row is given: melamine cyanurate, PFBS-K, KSS and stand-alone nanoclay are open items. Most of these systems are bought pre-dispersed, and the let-down ratios are on flame retardant masterbatch.

Table T5. Published loadings by system.

How Do You Select a Flame Retardant? 8 Steps#

Select a flame retardant in 8 steps: define the fire rating and thickness, check the processing temperature, decide between halogenated and halogen-free, choose the synergists, check side effects on properties, check smoke and acidity, screen the regulations, then compare cost-in-use and supply risk. Steps 1 and 2 remove more candidates than the other 6 together.

1. Define the fire standard, the class and the thickness. A specification that says "UL 94 V-0" without a thickness is incomplete; add the glow-wire values for appliances, the euroclass for cable and the hazard level for rail.
2. Check the processing temperature against the decomposition onset. ATH releases water from about 200 °C, APP phase II from about 240 °C with a processing ceiling near 220 °C, MDH stays stable to about 320 °C and AlPi decomposes above 300 °C, so engineering polymers at 240 to 320 °C rule out ATH and most APP.
3. Decide halogenated or halogen-free. An a1 acidity class and an electronic display housing under Ecodesign Regulation (EU) 2019/2021 make the decision before the compounder does.
4. Choose the synergist and the anti-drip package. Antimony trioxide for halogen donors, melamine polyphosphate for phosphinates, zinc borate for smoke and afterglow, PTFE at about 0.1 phr against flaming drips.
5. Check the effect on mechanical, thermal and electrical properties. 20 wt% of an aryl phosphate leaves PC/ABS with a heat deflection temperature of 72.6 °C; a phosphinate blend holds a comparative tracking index of 600 V; AlPi with melamine polyphosphate in PA66 can bloom after 85 °C and 85 % relative humidity.
6. Check smoke, droplet and acidity requirements, which the EU cable classes rate separately from heat release and which aircraft interiors cap at a smoke density of 200 at 4 minutes.
7. Screen the regulations in every market you sell into, using the regulatory matrix in the next section, and treat pending items as pending.
8. Compare cost-in-use and supply risk. Flame retardants took 39 % of US antimony end use on 2024 data, and the antimony price averaged USD 25 per pound in 2025 against USD 10.24 in 2024.

The general framework behind those 8 steps is on how to select plastic additives.

Screening by hand stops being practical above 3 or 4 candidates: filter systems with the flame retardant selector by polymer and UL 94 rating.

What is the best flame retardant?#

No flame retardant is best for every plastic: the best choice is the one that reaches the required rating at the lowest loading inside the polymer's processing window, such as AlPi with melamine polyphosphate in glass-filled polyamide, intumescent APP in polypropylene, or ATH and MDH in halogen-free cable. Environmental profile is a second filter rather than a substitute for the first: the EU-funded ENFIRO project (FP7 grant 226563, concluded 2012) found good environmental and health profiles for APP, aluminium diethylphosphinate, ATH, MDH, melamine polyphosphate, DOPO, zinc stannate and zinc hydroxystannate.

How Are Flame Retardants Tested?#

Flame retardants are tested with 8 main methods: UL 94 vertical and horizontal burning, the limiting oxygen index, the cone calorimeter, the glow-wire tests, cable fire tests under EN 50399, smoke density chambers, the FMVSS 302 burn rate for vehicle interiors and the EN 45545-2 hazard levels for rail. Each method answers a different question, and a compound that passes one can fail another, which is why a flame retardant is specified against a named test at a named thickness rather than against a general claim. All methods are indexed under testing plastic additives.

Table T7. Fire tests used to qualify flame retardants.

UL 94 ratings: V-0, V-1, V-2, HB and 5V#

UL 94 V-0 is the highest vertical burning class: each afterflame must stop within 10 s, the 5 specimens together may burn for at most 50 s, and no flaming drip may ignite the cotton below. The classes differ only in those 3 numbers plus the cotton result, which is what makes the ladder easy to read and easy to misquote without a thickness.

Table T6. UL 94 classification criteria.

The test conditions are fixed and the thickness is not. A V rating uses 5 bar specimens of 125 by 13 mm exposed twice for 10 s to a 20 mm, 50 W flame, conditioned for 48 h at 23 °C and 50 % relative humidity and, for the second set, for 7 days at 70 °C; the 5V tests use a 500 W flame about 5 times more severe. The same compound can rate V-0 at 3.2 mm and V-2 at 0.8 mm, so every rating on this site carries its thickness. Test set-up and edge cases are on UL 94 flammability ratings.

LOI, cone calorimeter and glow-wire tests#

The limiting oxygen index is the lowest oxygen concentration in a flowing oxygen and nitrogen mixture that keeps a plastic burning, so polypropylene at about 17.5 vol % O2 burns in air, which holds about 21 % oxygen, while intumescent polypropylene reaches 29 to 33 vol % O2. The method is defined in ASTM D2863-23e1 and ISO 4589-2, and the result is a comparative screening value rather than a pass or fail class. Values by polymer are on limiting oxygen index (LOI).

The cone calorimeter converts burning behaviour into engineering numbers. It was built by Vytenis Babrauskas and colleagues at the US National Bureau of Standards, now NIST, in 1982, and is standardised as ISO 5660-1 and ASTM E1354-26, at external heat fluxes of 35 and 50 kW/m2 in most published work. It measures heat release rate, total heat release, time to ignition and smoke, which is how the gap between neat polypropylene at 1,148 to 1,332 kW/m2 and an intumescent compound at 220 to 255 kW/m2 becomes visible; Bernhard Schartel and T. Richard Hull set out how to read those curves in Fire and Materials in 2007. Method detail is on cone calorimeter testing.

Glow-wire testing answers the appliance question rather than the material question: can a part ignite from an overheated contact? The tests are IEC 60695-2-11 on the end product, IEC 60695-2-12 for the glow-wire flammability index and IEC 60695-2-13 for the glow-wire ignition temperature, each with a 30 s application, and glass-filled PA66 with an Exolit OP phosphinate reaches 960 °C and 775 °C respectively. Criteria are on glow wire test (GWFI, GWIT).

Cable, transport and building fire classes#

EU cables are classed from Aca to Fca under EN 13501-6, with extra ratings for smoke from s1 to s3, for flaming droplets from d0 to d2 and for acidity from a1 to a3, and class B2ca allows a peak heat release of no more than 30 kW in the EN 50399 test. The class letter, the smoke rating and the acidity rating are 3 independent decisions for the compounder, and only the acidity rating forces the halogen-free choice outright.

Table T6b. EN 13501-6 classes and EN 50399 limits for cables.

The EN 50399 limit values above come from a cable maker's published class table, a secondary source; the standards named are primary. Test sequences and class logic are on cable fire tests and CPR classes.

Transport uses its own ladders: FMVSS 302 under 49 CFR 571.302 for road vehicle interiors, the EN 45545-2 requirement sets with hazard levels HL1 to HL3 for rail, and 14 CFR 25 Appendix F Part IV for aircraft. Aircraft adds a smoke criterion of a specific optical density of no more than 200 at 4 minutes, measured under ASTM E662 or ISO 5659-2, and the methods behind that criterion are on smoke density testing.

How Are Flame Retardants Regulated?#

Flame retardant regulation targets persistent halogenated flame retardants first: decaBDE, HBCD, SCCP and Dechlorane Plus are banned as persistent organic pollutants, and the EU is preparing a REACH restriction on non-polymeric aromatic brominated flame retardants, with a draft dossier planned for December 2026. The European Chemicals Agency set that direction in its regulatory strategy for flame retardants published in March 2023, which named aromatic brominated flame retardants as candidates for restriction and concluded that aliphatic brominated and organophosphorus flame retardants need more data.

Three instrument families do the work: REACH, through the Candidate List, Annex XIV authorisation and restrictions under preparation; the POPs Regulation (EU) 2019/1021, which implements Stockholm Convention listings; and product law, meaning RoHS, Ecodesign, the Toy Safety Directive and food contact rules. In the US the same job is done by TSCA section 6(h), California Proposition 65 and state product bans. Every rule that touches a flame retardant is summarised in flame retardant regulations.

Table T8. Regulatory status of 20 flame retardants and synergists.

"Not assessed on this page" means no verified value is held in this reference; it does not mean the substance is unregulated.

EU rules: REACH, POPs, RoHS and Ecodesign#

The EU controls flame retardants through the REACH Candidate List and Annex XIV, a restriction under preparation for non-polymeric aromatic brominated flame retardants, the POPs Regulation (EU) 2019/1021, RoHS and the Ecodesign ban on halogenated flame retardants in display housings. Flame retardant entries on the Candidate List run from HBCD on 28 October 2008 to DBDPE on 5 November 2025, and each one is tracked on the SVHC Candidate List page.

The 6 instruments that matter for a flame retardant specification are listed below.

• REACH restriction on aromatic brominated flame retardants (in preparation). ECHA published its investigation report on 18 December 2024, finding about 60 aromatic brominated flame retardants potentially on the EU market and 25 of them registered; the Commission issued its mandate on 11 November 2025; the call for evidence ran from 21 January to 18 March 2026; and the draft Annex XV dossier is planned for December 2026. The scope covers non-polymeric grades in electrical and electronic equipment, construction products and textiles, built around DBDPE, TBPH and BTBPE plus up to 24 substances in total. The timeline is tracked on EU restriction of aromatic brominated flame retardants.
• REACH Annex XIV (authorisation). HBCD is entry 3 and TCEP is entry 13, both with a sunset date of 21 August 2015, so neither may be used in the EU without an authorisation. Entry numbers are on REACH Annex XIV authorisation list.
• POPs Regulation (EU) 2019/1021. Delegated Regulation (EU) 2025/1482 sets the unintentional trace limit for the sum of tetra- to decaBDE at 10 mg/kg in mixtures and articles; HBCD carries 100 mg/kg; Dechlorane Plus carries 1,000 mg/kg until 15 April 2028 and 1 mg/kg after that under Delegated Regulation (EU) 2025/1930.
• RoHS Directive. Polybrominated diphenyl ethers are capped at 0.1 % in homogeneous materials, and the planned addition of TBBPA and MCCP to Annex II was dropped in 2024. Exemptions are on RoHS and plastic additives.
• Ecodesign Regulation (EU) 2019/2021. All halogenated flame retardants have been banned in the enclosures and stands of electronic displays since 1 March 2021, a ban upheld by the EU General Court.
• Toy Safety Directive 2014/79/EU. TCEP, TCPP and TDCP are limited to 5 mg/kg in toys for children under 36 months or intended to be placed in the mouth.

ECHA is also investigating organophosphorus flame retardants, the second half of the 2023 strategy; the reporting dates for that work are not established in this reference.

US rules: TSCA, Proposition 65 and state bans#

In the US, the EPA restricts decaBDE and PIP (3:1) under TSCA section 6(h), with PIP (3:1)-containing articles barred from distribution after 31 October 2026, while California's Proposition 65 lists antimony trioxide, TCEP, TDCPP, TBBPA and molybdenum trioxide as carcinogens. Federal action is substance-by-substance and state action is product-by-product, so a compound can be legal under TSCA and still be barred from a mattress sold in California.

The 4 instruments that decide a US flame retardant specification are listed below.

• TSCA section 6(h). The revised rule was published on 19 November 2024 (89 FR 91486) and took effect on 21 January 2025: decaBDE carries a 0.1 wt% threshold for unintentional presence, motor-vehicle replacement parts run to the end of service life or 2036, and PIP (3:1) articles may not be distributed after 31 October 2026 under 40 CFR 751.407. Deadlines are on TSCA and plastic additives.
• TSCA risk evaluations. The final TCEP risk evaluation was published in September 2024 and found unreasonable risk to workers, consumers and aquatic species; the TBBPA draft risk evaluation was released on 12 June 2026, with the final evaluation pending. The article restrictions on PIP (3:1) (isopropylated triphenyl phosphate) are already fixed.
• California Proposition 65. The 5 flame retardant cancer listings are antimony oxide on 1 October 1990, TCEP on 1 April 1992, TDCPP on 28 October 2011, TBBPA on 27 October 2017 and molybdenum trioxide on 19 March 2021; listing dates are on California Proposition 65.
• State product bans. California AB 2998 has banned halogenated and organophosphorus flame retardants above 1,000 ppm in juvenile products, mattresses and upholstered furniture since 1 January 2020; New York has banned organohalogen flame retardants in electronic display enclosures since 1 January 2024; Washington banned polybrominated diphenyl ethers in 2011 and added a Safer Products rule on organohalogen flame retardants in electric and electronic product casings in 2023.

Which flame retardants are POPs under the Stockholm Convention?#

Flame retardants have been listed as persistent organic pollutants at 5 Conferences of the Parties between 2009 and 2025, covering polybrominated diphenyl ethers, hexabromobiphenyl, HBCD, decaBDE, SCCP, Dechlorane Plus and MCCP. Every listing goes into Annex A, meaning elimination with specific exemptions, and the EU implements each one through the POPs Regulation (EU) 2019/1021. EU limit values are on POPs in plastics.

1. COP-4, 2009: tetra- to hepta-brominated diphenyl ethers and hexabromobiphenyl.
2. COP-6, 2013: hexabromocyclododecane (HBCD), with a building insulation exemption that has since expired.
3. COP-8, 2017: commercial decabromodiphenyl ether (decaBDE) and short-chain chlorinated paraffins (SCCP, effective December 2018).
4. COP-11, 2023: Dechlorane Plus, by decision SC-11/10, with specific exemptions.
5. COP-12, 2025: medium-chain chlorinated paraffins (C14 to C17, at least 45 % chlorine) by decision SC-12/10; the EU act C(2026) 6262 is adopted but not in force, and the substance page is MCCP (medium-chain chlorinated paraffins).
6. National implementation: Canada's SOR/2025-270 comes into force on 30 June 2026, covering HBCD as item 13, polybrominated diphenyl ethers as item 15 and Dechlorane Plus as item 24.

Who Makes Flame Retardants? Market Size and Manufacturers#

The flame retardant market is worth USD 8.1 to 9.3 billion on 2025 analyst estimates, and its largest producers include Albemarle, ICL and Lanxess for brominated and phosphorus flame retardants, Clariant for phosphinates and ammonium polyphosphate, and Huber and Nabaltec for mineral hydroxides. Analyst estimates differ because scope definitions differ, so this reference always states the value as a range. By volume the family passed 2 million tonnes in 2013, with Asia-Pacific holding 41 % of demand on 2010 data, and brominated grades accounted for 390,000 t in 2011, about 19.7 % of the total. Company profiles are in flame retardant manufacturers and suppliers.

Table T9. Flame retardant producers and their brand lines.

Two raw materials carry the supply risk. Antimony took 39 % of US end use as flame retardants on 2024 data, and its price averaged USD 25 per pound in 2025 against USD 10.24 in 2024, after China introduced export licences in August 2024 and banned exports to the US in December 2024; world mine production is estimated at 110,000 t of antimony for 2025, with China at 40,000 t (USGS Mineral Commodity Summaries 2026). Bromine is the second, with world production outside the US estimated at 400,000 t for 2024 and Israel at 140,000 t. Price trends are tracked on antimony trioxide price.

Segment splits, raw material chains and regional capacity are on flame retardants market.

Complete List of Flame Retardants: All 56 Substance Pages#

The complete list below gives all 56 flame retardants and synergists covered on this site, grouped by the 13 types, with CAS number, main host polymers and regulatory flag. The flag column reports only what this reference holds as verified: a REACH Candidate List entry, a Stockholm POP listing or a California Proposition 65 cancer listing.

Table T10. All 56 flame retardant substances.

"None listed" means the substance is not on the REACH Candidate List, is not a Stockholm POP and is not among the Proposition 65 flame retardant entries held in this reference; it does not mean it is unregulated. Type 13, nanocomposite flame retardants, has no substance page yet, and the chlorinated paraffins SCCP, MCCP and LCCP are catalogued in the plasticizer family. Filter every substance by CAS, function, dosage and regulatory status in the plastic additives database.

Are Flame Retardants Toxic?#

Some flame retardants are toxic or persistent, such as the carcinogen TBBPA, the reproductive toxicant TCEP and the banned pollutants decaBDE and HBCD, while mineral and phosphinate flame retardants such as ATH, MDH and aluminium diethylphosphinate are not substances of very high concern. The family is a spread of hazard profiles rather than one.

TBBPA carries a harmonised Carc. 1B H350 classification from 1 September 2025 under Delegated Regulation (EU) 2024/197 and has been on the REACH Candidate List since 17 January 2023. TCEP carries Carc. 2 H351 and Repr. 1B H360F and has been on the Candidate List since 13 January 2010. Antimony trioxide carries Carc. 2 H351 and was evaluated by IARC as Group 2A in 2022, and decaBDE and HBCD are Stockholm Convention pollutants. Against that, ATH has no harmonised CLP entry, and ATH, APP, aluminium diethylphosphinate and zinc stannate are not on the Candidate List. Exposure data explains the public interest: Heather Stapleton and colleagues found flame retardants in 85 % of 102 US couches in a 2012 study. Exposure studies are on flame retardants and human health.

Is there a non-toxic flame retardant?#

No flame retardant is free of all hazard, but the EU-funded ENFIRO project (FP7 grant 226563, concluded 2012) found good environmental and health profiles for 8 halogen-free options: ammonium polyphosphate, aluminium diethylphosphinate, ATH, MDH, melamine polyphosphate, DOPO, zinc stannate and zinc hydroxystannate. The same project found that RDP and BDP in styrenics produced more smoke, a reminder that hazard profile and fire performance are 2 separate assessments. The answer also depends on loading, because a flame retardant used at 60 wt% raises different questions from one used at 0.4 wt%.

Do flame retardants save lives?#

Flame retardants can buy escape time: in 1988 room-scale tests by the US National Bureau of Standards, flame-retarded products gave more than 15 times the available escape time and released one quarter of the heat of untreated products. That result applies to the products tested at room scale, not to every flame retardant at every loading. The counter-case is furniture foam, where California replaced the open-flame foam test of TB 117 with the smoulder test on cover fabric in TB 117-2013, effective in 2014.

Legacy flame retardants in recycled plastic#

Recycled plastic from old electronics can still contain decaBDE, so the EU allows only 350 mg/kg of polybrominated diphenyl ethers in articles made from recovered material from 30 December 2025, falling to 200 mg/kg from 30 December 2027, and 10 mg/kg for toys and childcare articles from recovered material from 17 May 2027. decaBDE was used at scale in HIPS television and computer housings, exactly the stream that feeds electronics recycling today. Detection and sorting are covered on legacy additives in recycled plastic.

These limits are unintentional trace contaminant values rather than permitted additions, and the general limit for the sum of tetra- to decaBDE in mixtures and articles is 10 mg/kg under Delegated Regulation (EU) 2025/1482. Under US TSCA, recycled plastic is excluded from the decaBDE prohibition where no decaBDE was added. The concept is defined on unintentional trace contaminant (UTC).

Flame retardants outside plastics: textiles, coatings and wood#

Fire-retardant sprays, intumescent paints, wood treatments and textile finishes share much of the chemistry but are outside this plastics reference. Ammonium polyphosphate, for example, is the acid source of intumescent coatings as well as of intumescent polypropylene, and it is covered here only for its use in plastics.