How FR Treatment Works: A Plain-English Guide for Interior Designers

What FR treatment does: It slows or prevents the ignition and spread of flame by interfering with the chemistry of combustion at the surface of the fabric.
The two main methods: Back-coating (paste applied to the reverse — standard for upholstery Crib 5) and wet padding (chemical solution applied to the whole fabric — standard for curtain treatment).
Inherent vs topical: Inherent fire resistance is a permanent property of the fibre itself. Topical treatment is applied after weaving and can degrade over time, through cleaning, or through interaction with certain dyes.
Who can certify: Only a UKAS-accredited testing laboratory. No fabric company, designer, or treatment provider can self-certify.

Most interior designers who specify FR-treated fabrics regularly have never seen the treatment process and have only a general idea of how it works. This guide explains the chemistry and process in plain language — not to make designers into treatment specialists, but to give them enough understanding to ask the right questions, spot specification risks before they become problems, and explain FR compliance confidently to clients and contractors.

For which fibres can be treated, see our FR treatment and fibre compatibility guide. For dye types and their interaction with treatment, see our dye types and FR treatment guide. For the fire standards that require treatment, see our Crib 5 guide.

Why Fabrics Need FR Treatment

All organic fibres will burn if exposed to sufficient heat and ignition energy. The chemistry of combustion in textiles follows a consistent pattern. When a fibre is heated, its polymer structure begins to break down — a process called pyrolysis. This produces flammable gases. The gases mix with oxygen from the atmosphere and ignite, producing a flame. The flame generates further heat, which causes more pyrolysis, which produces more flammable gas, which sustains and spreads the fire. This self-reinforcing cycle is what makes unprotected upholstery and curtains a serious fire hazard in public buildings.

FR treatment breaks this cycle at one or more points. Depending on the type of FR compound used, it may prevent or delay pyrolysis, reduce the quantity or flammability of the gases produced, cause the fabric to form a carbonaceous char layer that insulates the underlying structure from the heat source, or dilute the flammable gases with inert gases that cannot sustain combustion. The goal in all cases is the same: to prevent the fabric from sustaining ignition and propagating flame when exposed to the ignition sources defined in the test standard.

The Two Main Treatment Methods

Back-coating. The standard method for upholstery Crib 5 treatment. The fabric is passed through a machine that applies a paste or emulsion of FR chemicals to the reverse face of the fabric. The paste is then dried and cured to fix the compound to the backing structure. The treatment sits on the back face and does not penetrate the face yarns. This is why back-coating, when correctly applied, does not alter the appearance or handle of the face fabric.

The FR compounds used in back-coating are typically phosphorus-based or halogenated compounds — most commonly brominated flame retardants applied in a paste that also contains a binder to hold the compound to the fabric. The phosphorus compounds work primarily in the solid phase: when heated, they decompose to form phosphoric acid, which causes the polymer to char rather than produce flammable gases. The halogenated compounds work primarily in the gas phase: they release halogen radicals that interrupt the chain reactions sustaining the flame.

Back-coating adds weight to the fabric — typically a few grams per square metre — and gives the reverse a firmer, slightly stiffer character. This can be an advantage in upholstery construction because the stiffer back helps the fabric behave consistently during cutting and making-up. It does not affect the face pile character of velvet or the handle of the woven face.

Wet padding. The standard method for curtain FR treatment and some lighter upholstery fabrics. The fabric is fed through a padder — a bath of FR chemical solution followed by rollers that squeeze the solution into the fabric structure under controlled pressure — and then dried and cured. The wet pickup is controlled to achieve the required chemical loading. Because the solution penetrates the whole fabric including the face yarns, wet padding can affect handle and, critically, can interact with certain dye types. See the dye types and FR treatment guide for the specific risks.

The FR compounds used in curtain wet padding are typically water-soluble inorganic salts — ammonium phosphate or ammonium sulphate compounds — applied in aqueous solution. These are effective for cellulosic fibres and work primarily by releasing inert gases when heated that dilute the flammable gas mixture around the burning fabric. They are less suitable for upholstery because they are water-soluble and would wash out in cleaning. Back-coating compounds are insoluble and more durable.

Inherent Fire Resistance vs Topical Treatment

The distinction between inherent and topical fire resistance is commercially significant and frequently misunderstood.

Inherent fire resistance is a permanent property of the fibre itself, arising from its chemical structure. Wool and mohair have inherent fire resistance because they are protein fibres with high nitrogen and sulphur content. These elements make the fibre self-extinguishing — when the ignition source is removed, the fibre stops burning. No chemical treatment is required and no treatment can be washed away. The fire resistance is permanent for the life of the fabric.

Trevira CS is an inherently flame-retardant synthetic fibre. The flame-retardant chemical is incorporated into the polyester polymer during fibre production, not applied to the surface afterwards. Like mohair, the fire resistance is permanent and survives cleaning.

Topical treatment applies FR chemicals to the fabric after it has been woven or knitted. The chemicals are not part of the fibre structure — they sit on or within the fabric surface. This means they can potentially be degraded by cleaning, by mechanical abrasion over time, or by interaction with atmospheric pollutants or incompatible dyes. The degree to which this happens depends on the specific FR compound, the fabric construction, and the cleaning regime.

Back-coated fabrics retain their FR properties well under normal contract cleaning conditions because the back-coating compound is insoluble and mechanically fixed to the backing structure. The relevant risk is the dye interaction problem in wet-padded fabrics described in the dye types guide rather than the physical removal of the compound.

For contract environments where cleaning frequency is high — healthcare, transport seating, hotel restaurants — the distinction between inherent and topical certification carries practical weight. A fabric whose fire resistance survives aggressive cleaning without needing re-treatment or re-certification is operationally simpler and more reliably compliant over its full service life.

The Testing and Certification Process

FR treatment produces a claim of compliance. The claim must be verified by an independent test before it has any legal or commercial standing.

The test is conducted by a UKAS-accredited testing laboratory. The fabric and, for composite tests such as BS 7176, the filling material as well, are prepared and tested against the relevant ignition sources. For BS 5852 Crib 5, the ignition source is a wooden crib of defined dimensions and mass placed at the junction between a test seat and back assembly made from the fabric and a standard filling. The assembly must show no sustained flaming or progressive smouldering after the crib has burned out.

If the assembly passes, the laboratory issues a test certificate. The certificate identifies the fabric by name or reference, the filling used in the test, the standard tested against, and the test result. This certificate is the document that a designer must obtain from the fabric supplier and retain as evidence of compliance for the project.

A fabric supplier’s claim that a fabric is Crib 5 compliant without a certificate from a UKAS-accredited laboratory is not sufficient for contract specification. The Regulatory Reform (Fire Safety) Order 2005 requires the responsible person for a building to be able to demonstrate that furnishings comply with the applicable standard. A verbal assurance or a product description are not adequate evidence. The test certificate is.

What FR Treatment Cannot Do

Understanding the limits of FR treatment is as important as understanding what it achieves.

FR treatment cannot make a fabric fireproof. No textile can be made completely non-combustible by topical treatment. FR treatment reduces ignitability and slows flame spread sufficiently to meet the defined test standard. In a real fire involving sustained heat and ignition energy beyond the test conditions, treated fabric will eventually burn.

FR treatment cannot compensate for incorrect installation. A Crib 5-certified fabric used without the foam specified in the test certificate does not maintain its certification. The certificate is issued for the specific fabric and filling combination tested. Substituting a different foam invalidates the certificate for that assembly.

FR treatment does not substitute for structural fire safety. The fire resistance of the building fabric — walls, floors, doors, compartmentation — is a separate matter from the fire safety of soft furnishings. FR upholstery fabric is one element of a fire safety strategy, not a substitute for the rest of it.

FR treatment does not make a fabric immune to cleaning degradation permanently. Back-coated fabrics are durable under normal cleaning conditions, but cleaning with inappropriate chemicals — very high pH alkaline cleaners, solvents incompatible with the binder system — can over time affect the integrity of the coating. The cleaning code on the fabric data sheet should be followed.

What Happens When a Treated Fabric Is Cleaned

The question designers are most frequently asked by clients is whether the FR treatment survives cleaning. The answer depends on the treatment method and the cleaning agent.

Back-coated upholstery fabrics coded S (solvent clean only) should not be cleaned with water-based products. The binder system holding the back-coating to the fabric may be water-sensitive. Repeated water-based cleaning of an S-coded back-coated fabric can progressively weaken the adhesion of the coating. The FR compound may remain present but its mechanical adhesion to the fabric is reduced.

Back-coated fabrics coded W or WS can be spot-cleaned with water-based products without significant effect on the back-coating, provided the products are not strongly alkaline. Hotel-grade alkaline cleaners applied repeatedly can over time affect the coating. This is one of the reasons to prefer inherently fire-resistant fabrics for hotel environments with high-frequency professional cleaning. See our hotel fabric specification guide for practical guidance on this.

Wet-padded curtain fabrics treated with water-soluble inorganic salt compounds are water-sensitive by nature. The standard BS 5867 Part 2 Type B test includes a water-soak stage precisely to assess whether the treatment survives cleaning. A fabric that passes this stage has demonstrated that its treatment survives a defined level of water exposure. This does not mean the treatment is permanent under repeated laundering. For healthcare curtain applications requiring Type C certification, a more rigorous laundering pre-conditioning is included in the test.

The Treatment Supply Chain

Understanding who is responsible for what in the FR treatment supply chain helps designers avoid the most common specification failures.

The fabric supplier is responsible for knowing whether their fabric can be treated, which treatment method is appropriate, and which treatment providers have successfully treated their fabric before. A good fabric supplier maintains this information and can advise the designer before the fabric is ordered.

The treatment provider applies the FR compound and, in most cases, arranges testing through a UKAS-accredited laboratory. The treatment provider issues the test certificate. They are responsible for the quality and consistency of the treatment and for ensuring the treated fabric meets the specified standard.

The designer is responsible for specifying the correct standard for the project, confirming that the fabric supplier and treatment provider can meet it, and obtaining the test certificate before the fabric is installed. The designer cannot certify compliance — only the testing laboratory can do that — but the designer is responsible for ensuring the certified fabric is what is installed.

The contractor or upholsterer is responsible for installing the certified fabric with the certified filling. Substituting materials without re-testing invalidates the certificate. The contractor should be briefed on this before work begins.

Frequently Asked Questions

Does FR treatment change how a fabric looks or feels?

Back-coating, correctly applied to the reverse of an upholstery fabric, does not alter the appearance or handle of the face. The back will feel slightly firmer and heavier but the face pile character and surface quality are unchanged. Wet padding for curtain treatment can affect the handle of lightweight or delicate fabrics — sheers in particular may feel slightly stiffer after treatment. Any fabric where handle or appearance change would be commercially significant should be sample-treated and approved before committing to the full order.

How long does FR treatment last?

Inherent fire resistance is permanent. Topical back-coating is durable under normal contract conditions and will typically remain effective for the life of the fabric provided it is cleaned according to the cleaning code and not subjected to chemicals that attack the binder system. Wet-padded treatments are less durable and may require re-treatment after intensive cleaning or after a defined number of years in high-frequency cleaning environments. For healthcare curtains under BS 5867 Type C, re-treatment after a defined number of wash cycles is standard practice.

Can a fabric be re-treated after cleaning?

Yes, in most cases. Back-coated upholstery fabrics that have been in service for many years can typically be re-treated if the original treatment has degraded, though this requires removing the fabric from the furniture. Wet-padded curtain fabrics can be re-treated when they are laundered if the treatment has been removed. The re-treated fabric must be re-tested if a new certificate is required. Contact the original treatment provider for advice on re-treatment for specific fabrics.

What is the difference between Crib 5 and BS 7176?

BS 5852 Crib 5 is the test method — the specific ignition source and test procedure. BS 7176 is the specification standard for non-domestic upholstered seating that references Crib 5 and additionally includes the cigarette and match tests, a water-soak stage, and documentation of the specific hazard category and filling used. For hotel and contract upholstery, BS 7176 Medium Hazard is the correct standard to specify because it produces a more complete and defensible certificate than Crib 5 alone. See our Crib 5 guide and hotel fabric specification guide for full detail.

Can I self-certify that a fabric is fire retardant?

No. Only a UKAS-accredited testing laboratory can issue a valid fire test certificate. A fabric supplier, designer, treatment provider, or contractor cannot self-certify FR compliance. Under the Regulatory Reform (Fire Safety) Order 2005, the responsible person for a commercial building must be able to produce evidence of compliance. A test certificate from a UKAS-accredited laboratory is that evidence. A verbal assurance, a product description, or a supplier’s own claim of compliance are not.

For the fire standards requiring treatment, see our Crib 5 guide. For which fibres can be treated, see our FR treatment and fibre compatibility guide. For dye types and their FR interaction, see our dye types and FR treatment guide.