Building Cable Fire Compliance: IEC 60332, CPR and BS 6387 Compared

Most compliance arguments about building cable are not arguments about fire. They are arguments about vocabulary. One engineer quotes a Euroclass, another quotes a fire-resistance duration, a third quotes a bundle test category, and all three are describing different properties of different test specimens. The cable is then either over-specified or rejected for the wrong reason.

01Two questions, two standards families, one common mistake

That distinction is not a matter of interpretation. The Construction Products Regulation applies to reaction-to-fire performance; the harmonised standard for fire-resistant cables is still in preparation, which is why fire-resistant cables cannot currently carry a CPR declaration at all (see section 03). The two families exist because they were written by different committees for different purposes.

02IEC 60332: what the test numbers actually measure

IEC 60332 is a family of test methods, not a product standard. It tells you how a specimen behaved in a flame; it does not tell you which cable to buy. Two parts matter for building cable, and they are routinely confused with each other.

IEC 60332-1-2 — one wire, one flame

This is the single-insulated-wire vertical flame test, and it is the one that appears on nearly every low-voltage datasheet as the line "flame retardant: IEC 60332-1". A single finished cable is mounted vertically and a 1 kW pre-mixed flame is applied. For specimens up to 25 mm diameter the flame is applied for 60 seconds; larger diameters are given progressively longer exposure. The assessment is made on how far the charring travelled.

One thing worth knowing: the current edition is IEC 60332-1-2:2025, Edition 2.0, published in June 2025, which reworked the specimen positioning rules and moved the performance criteria into an annex. Datasheets that simply say "IEC 60332-1-2" without a year are now ambiguous — the 2004 edition is still widely cited by test houses and by EN 13501-6.

IEC 60332-3-22 to -25 — the bundle test, and what "Category" really means

In the bundled test, cables are fixed to a vertical ladder and a flame is applied to the bottom. The difference between Categories A, B, C and D is not a difference in fire resistance of the compound. It is a difference in how much non-metallic material is on the ladder — which is the variable that governs whether a fire can propagate at all.

Volumes and durations per IEC 60332-3 series (Category A figure verified against the IEC webstore entry for IEC 60332-3-22; B/C/D loadings cross-checked against two independent cable-maker technical pages). Pass criterion is that the flame does not propagate beyond the marked zone after the burner is removed. There is also a variant written as A F/R (IEC 60332-3-21) using a two-layer ladder at 7 L/m for 40 minutes.

03The CPR Euroclass ladder: how to read it, and what changed in 2026

In the European Union, cables are construction products. Since 2017, a power, control or communication cable placed on the EU market must carry a Declaration of Performance for reaction to fire, and the declared class comes from EN 13501-6. The harmonised standard that turns the test results into that class is EN 50575, and it points to four test methods: EN 60332-1-2, EN 50399, EN 61034-2 and EN 60754-2.

Thresholds transcribed from Delegated Regulation (EU) 2016/364, Annex, Table 4 (OJ L 68, 15.3.2016, p. 4–11). Note that several trade pages circulating on the web give different figures — for example a THR₆₀₀ of 7.5 MJ for B1ca, or FIGRA ≤ 400 W/s for Cca. Those do not match the Regulation. Where a claim conflicts with the OJ text, the OJ text governs. FIGRA = fire growth rate; THR₁₂₀₀ = total heat released in the first 1,200 s.

Additional classifications: the letters after the dash

A class is rarely declared alone. Three extra groups travel with it, and they are the reason a single cable can be perfectly acceptable in one part of a building and rejected in another:

• Smoke (s1, s1a, s1b, s2, s3) — s1 caps total smoke production during the test; the a/b suffix distinguishes the light-transmittance figure measured under EN 61034-2. s3 means no smoke limit.
• Flaming droplets (d0, d1, d2) — d0 means none within the test period; d1 allows none that persist beyond 10 seconds; d2 is unrestricted.
• Acidity (a1, a2, a3) — derived from EN 60754-2, where a1 corresponds to the lowest conductivity and the highest pH. This is the halogen-acid proxy that sits behind most "LSZH" claims.

So Cca-s1b,d1,a1 reads as: flame spread and heat release at the Cca level; smoke production within the s1 band, with the s1b light-transmittance figure; limited flaming droplets; and the lowest acidity band. When a buyer asks us what a competitor's "Cca cable" is worth, the answer depends entirely on those nine characters — and they are the part most often omitted from a quotation.

What changed on 8 January 2026

04BS 6387 and EN 50200: the circuit-integrity side

Everything above concerns what a cable does to a fire. The UK system for life-safety circuits asks the opposite question: does the conductor survive long enough to keep a pump running or a door closing while the fire is in progress.

The classification most people quote is BS 6387, whose current edition is BS 6387:2013 and which retains only three categories. This is where a great deal of stale information circulates.

BS 6387:2013 applies to cables rated up to 600/1000 V with an overall diameter not exceeding 20 mm. A cable passing all three categories is described as Category CWZ. The standard is a test method, not a product standard — it classifies performance, and the product itself is specified under a separate standard.

Where BS 6387 stops, and what takes over

The 20 mm ceiling is the point most often missed. Above it — which is to say, most power cables — the UK route for demonstrating fire integrity of a cable system is BS 8491, which applies a flame plus direct impact plus a water jet and reports survival in 30, 60 or 120 minute bands. This is why armoured fire-resistant power cables are described with numbers such as F30, F60 and F120 rather than with CWZ.

• BS 8491 — fire integrity of large-diameter (over 20 mm) power cables, at 842 °C with impact and water, in 30/60/120 minute steps.
• EN 50200 — small cables with fire plus mechanical shock, classified PH 15 / 30 / 60 / 90 / 120. Widely used for fire detection and alarm circuits. Note that sources differ on the test flame temperature for this standard, quoting either 830 °C or 842 °C; we give both rather than pick one.
• BS 8434-2 — a tougher UK variant applying a 930 °C flame with water for up to 120 minutes, used where a specification calls for the enhanced route. BS 8434-1 has been withdrawn.
• BS 7629-1 — the product standard for screened fire-resistant cables used in fire detection, alarm and emergency lighting, in Standard 30/60 and Enhanced 120 grades.
• IEC 60331 — the international fire-with-fire equivalent family, used where the project is IEC-based rather than UK-based. The differences between IEC 60331 and BS 6387 are enough to change a buying decision, and we compare them separately.

05Matching the class to the building, not to the catalogue

Compliance fails most often not because a class is wrong, but because the class was chosen from a catalogue rather than from the space the cable runs through. The same building will legitimately contain Cca cable in one riser and a fire-resistant circuit in another.

This table maps questions to regimes, not products to buildings. Local codes — and your insurer — may layer additional requirements on top, in particular for tunnels, hospitals and high-rise. Nothing here overrides the project specification.

06Reading a fire class off a datasheet: the fields worth checking

A fire-performance claim is only as good as the document behind it. These are the eight fields we check, in order, whenever a quoted class matters to a project.

• Full class string, not just the main class. "Cca" alone omits smoke, droplets and acidity — which are frequently the deciding parameters.
• Test standard with edition or year. IEC 60332-1-2 without a year cannot be distinguished from the superseded 2004 text now that Edition 2.0 exists.
• Notified body and DoP number for CPR-declared products, and whether the AVCP system matches the class (the higher classes involve notified-body involvement).
• Specimen loading for any bundle test claim — category, and whether the tested construction matches the cable you would actually receive.
• Diameter when a circuit-integrity claim is made: under or over 20 mm decides whether BS 6387 or BS 8491 is the applicable route.
• Which sheath material the class was certified on. A compound change after certification invalidates the declaration unless it is re-tested; this is a common gap on private-label ranges.
• Test report date against the standard edition in force at that date.
• Whether the certificate names the factory. A certificate naming a trading company rather than a production site cannot be verified by inspection, which matters at site acceptance.

The five declarations we see overreach most often

1. "CPR certified" used as a synonym for fire resistant. The Regulation covers reaction to fire only; a fire-resistant cable cannot currently be CE marked for its resistance performance at all.
2. "LSZH" without test figures. Low smoke and zero halogen are measurable properties under EN 61034-2 and EN 60754-2. Note also that the widely quoted "halogen-free means less than 5 mg/g HCl" figure is a contractual convention rather than a threshold stated in EN 60754-1 itself.
3. "Flame retardant to IEC 60332-3 Cat A" on a cable whose construction was never bundle-tested, only single-wire tested.
4. "Withstands 950 °C for 3 hours" quoted from a BS 6387 test on a 15 mm control cable and applied to a 95 mm² power cable that would fall outside the standard's scope.
5. "Halogen free, therefore low smoke." Halogen-free compounds can still produce dense smoke unless the formulation is designed for it; the two properties are tested under different standards.

07The US route, in one paragraph per layer

North America asks the same questions through different documents, and it separates them more sharply than the EU does. Installation is governed by NFPA 70, the National Electrical Code, which is prescriptive about where a cable type may be used. Product construction splits between UL 44 for thermoset-insulated conductors and UL 83 for thermoplastic-insulated ones — the difference that produces the familiar XHHW versus THHN distinction. Flame and smoke performance for cables in trays is assessed under UL 1685, with plenum spaces handled by the stricter NFPA 262 Steiner tunnel test. Circuit integrity is a separate listing entirely: UL 2196 rates cables for one or two hours of survival, and where a survivability time is mandated it is the electrical code and NFPA 72 that require it, not the cable standard on its own.

For projects that must satisfy both worlds — a US-owned facility in the UK, for instance — the practical trap is that a cable listed to UL 1685 is not automatically compliant with a CPR class, and the reverse. The two schemes test differently, on different specimens, and neither recognises the other's declaration.

08What we publish, and what we will not pretend to publish

We build low-voltage power and building cable: XLPE-insulated, PVC- or LSZH-sheathed, unarmoured and steel-wire-armoured, to IEC 60502-1 and BS 5467, with flame propagation per IEC 60332-1 and halogen-free and low-smoke properties per IEC 60754-1/-2 and IEC 61034 where the LSZH construction is specified. Those are the ratings on our own product pages, and we quote them as published, not as extended.

What this page deliberately does not do is claim a certification we do not hold. We do not hold a CPR Declaration of Performance for a fire-resistant cable system, because no harmonised standard for that performance exists yet. We have not listed this article against BS 8491, EN 50200 or UL 2196, and we do not publish certificates we cannot put a factory name against. If your project needs a circuit-integrity grade, tell us the required survival band and we will tell you plainly whether we can supply it or whether you should be talking to a specialist manufacturer. That answer costs us some enquiries. It prevents far more site rejections.