Cable Reaction-to-Fire Classification (Cca) — BS 7671:2018+A4:2026 & the CPR

Cables are one of the most common combustible loads in any modern building. In a fire, the sheath and insulation contribute to flame spread, generate smoke and hot gases, release flaming droplets that ignite secondary fires, and produce acid gases that attack life-safety electronics and the people trying to escape. The Grenfell Tower Inquiry and a series of European apartment-block fires have repeatedly forced the question: how flammable is the cable, and how much smoke does it make?

For decades the UK answer was "non-flame-propagating to BS 4066-3" or the broadly equivalent IEC 60332. From 2017 that was replaced by a harmonised classification under the Construction Products Regulation, set out in BS EN 50575. Every power, control or communication cable for permanent installation now carries a single Euroclass letter from Aca down to Fca, plus subclass codes for smoke, droplets and acidity. BS 7671:2018+A4:2026 references this classification through Chapter 42 (Protection Against Thermal Effects) and Chapter 52 (Selection and Erection of Wiring Systems).

Cable reaction-to-fire is not just a BS 7671 question — it sits inside a stack of overlapping legislation, retained EU law and product standards. Understanding which layer says what is the difference between a defensible specification and a costly retrofit.

1. Construction Products Regulation (EU) 305/2011 — retained as UK law after Brexit. Places obligations on manufacturers placing cable on the UK market: classify, declare the performance, mark the product, retain the technical file.
2. BS EN 50575 — the harmonised product standard for power, control and communication cables in construction works subject to reaction-to-fire requirements. Defines the test, the classification and the Declaration of Performance content.
3. BS 7671:2018+A4:2026 — the UK Wiring Regulations. Chapter 42 and Chapter 52 require the designer to select cable suitable for the fire risk of the location, with particular attention to escape routes and safety services.
4. Regulatory Reform (Fire Safety) Order 2005 — the Responsible Person duty for non-domestic premises and the common parts of HRBs. Cable choice supports the wider fire strategy and risk assessment.
5. Building Safety Act 2022 + Fire Safety (England) Regulations 2022 — for higher-risk buildings (18 m+ or 7 storeys+) the Building Safety Regulator regime applies. For 11 m+ residential blocks, evacuation and information duties intensify, and protected escape routes must demonstrably resist fire propagation.
6. Approved Document B (Vol 1 dwellings, Vol 2 other) — practical guidance on meeting Building Regulations fire safety requirements, referencing reaction-to-fire classifications for materials in escape routes.

The Euroclass system rates cable reaction to fire on a sliding scale from Aca (non-combustible) at the top down to Fca (no performance determined) at the bottom. Classification is determined by laboratory testing under BS EN 50399 (the Single Burning Item or SBI test, derived from EN 13823) for the higher classes and EN ISO 1716 or EN 60332-1-2 for the others. Each class reflects measured fire performance — heat release, flame spread, total heat output and burning duration.

1. Aca — non-combustible (gross calorific value test EN ISO 1716). Almost never seen in cable form because the sheath material has to be effectively non-combustible. Reserved for the most safety-critical applications.
2. B1ca — extremely limited contribution to fire, very low heat release, no flame spread beyond the burner area. Used in tunnels, underground systems and very high-risk premises.
3. B2ca — very limited contribution to fire. Stricter than Cca on heat release and flame spread. Used in escape routes of high-occupancy public buildings and increasingly specified for high-rise residential common parts.
4. Cca — limited contribution to fire. The widely specified "fire-safe" class for protected escape routes, basements, high-rise residential common parts and assembly buildings.
5. Dca — acceptable contribution to fire. Suitable for ordinary commercial and domestic applications outside escape routes. Most general-purpose CPR-compliant power cable sold in the UK is at least Dca.
6. Eca — limited flame propagation (the BS EN 60332-1-2 single vertical wire test passed). The basic CPR floor — broadly equivalent to the legacy "non-flame-propagating" UK requirement.
7. Fca — no performance determined or below Eca. Effectively means "no fire performance claim made" — would not normally be acceptable for fixed installations in occupied buildings.

A primary Euroclass on its own is incomplete. For B1ca, B2ca, Cca and Dca, the classification must be followed by additional codes describing smoke production, flaming droplets and the acidity of combustion gases. The full classification reads like "Cca-s1b,d1,a1" — the most commonly specified high-performance code in UK escape routes.

In escape routes, the difference between Cca-s3,d2,a3 (the bare primary class with no subclass declarations) and Cca-s1b,d1,a1 (limited smoke, no persistent droplets, low acidity) is enormous. The first may satisfy a manufacturer's minimum legal obligation but be unsuitable for occupied escape routes. The second is the industry-recognised high-performance UK specification.

Class selection is led by the building's fire strategy, Approved Document B and BS 7671 Chapter 42, not by a flat "always use Cca" rule. The typical mapping below is what most UK fire engineers and designers use as a starting point — always confirm with the project fire strategy.

BS 7671 also imposes parallel requirements for safety services — fire alarm circuits per BS 5839 and emergency lighting per BS 5266. Those circuits typically use enhanced fire-resistant cable (BS EN 50200 / BS 8434) in addition to the reaction-to-fire requirements set out here. Fire resistance (does the circuit keep working in a fire?) and reaction to fire (how does the cable contribute to fire?) are complementary duties, not interchangeable.

A4:2026, published 15 April 2026 and effective 27 September 2026, did not rewrite the reaction-to-fire framework — that remains in BS EN 50575 and the CPR. What A4:2026 did do was reinforce the cable selection duty within Chapters 42 and 52 and align the regulations with the post-Grenfell, post-Building Safety Act landscape.

1. Regulation 422.2 (Conditions of evacuation in an emergency) — the obligation to select cabling on escape routes that does not unduly propagate fire and limits smoke is retained and reinforced. A4:2026 cross-references the Euroclass system explicitly in the Notes.
2. Regulation 527 (Selection and erection to minimise the spread of fire) — the requirement to use cables compliant with BS EN 50575 and to declare the Euroclass classification carries through. A4:2026 clarifies that the Declaration of Performance is part of the project documentation.
3. Chapter 56 (Safety services) — circuits for fire detection and alarm, emergency lighting and other safety services must maintain operation for the required duration; this is fire resistance, not reaction to fire, but A4:2026 reminds the designer that the cable must satisfy both duties.
4. Schedule of Inspections — A4:2026 introduces refreshed inspection columns; the inspector is expected to verify that cabling selected for escape routes is consistent with the project fire strategy and the declared Euroclass.
5. Selection and erection in higher-risk residential — A4:2026 brings the regulations into alignment with the practical fire strategy expected for buildings over 11 m, with a clearer signal that Cca-s1b,d1,a1 is the floor for protected routes.

Walk onto any commercial fit-out and someone will tell you "we're using LSZH so we're fine for Cca". They are not the same thing. LSZH (Low Smoke Zero Halogen) describes the cable's chemistry — sheath and insulation formulated to produce limited smoke and to contain no halogens (so combustion will not generate hydrogen chloride or other acid gases). It is a material property, not a tested performance.

Cca is a tested classification under BS EN 50575 — the cable as a finished construction has been subjected to the SBI test and achieved measured limits on heat release, flame spread and total heat output. A cable can be LSZH chemistry but only achieve Dca or Eca on the SBI test; conversely a cable can achieve Cca without being LSZH if its overall burn behaviour meets the limits. The two are correlated but not identical.

For decades the UK domestic and small-commercial market relied on BS 6004 (general PVC twin-and-earth, now superseded by BS EN 50525) and BS 7211 (low-smoke fume thermosetting cable). These are still made, but under the CPR they now must additionally carry a Euroclass — and that classification typically sits at the lower end of the spectrum.

For specialised cable applications in life-safety circuits, see also our MICC (Pyro) cable guide — mineral-insulated copper-clad cable remains the canonical fire-resistant solution for the most critical circuits, and modern MICC achieves the top end of the Euroclass spectrum.

Every fixed-installation cable placed on the UK market must carry a conformity marking and be accompanied by a Declaration of Performance (DoP) — the manufacturer's legally binding declaration of the cable's Euroclass, the tests undergone, the notified body that supervised the testing, and the product's identification details.

1. CE marking — historically recognised across the EU and in the UK. Post-Brexit, CE marking is still accepted in Great Britain on construction products under indefinitely extended transitional arrangements (re-confirmed by government as of 2026).
2. UKCA marking — the UK's own conformity mark, accepted in Great Britain. In Northern Ireland the CE / UKNI arrangements apply under the Windsor Framework.
3. Declaration of Performance (DoP) — a written declaration in a defined format including: product type, intended use, AVCP system, notified body, declared performance against each essential characteristic (reaction to fire being the key one for cable), and the manufacturer's signature.
4. Product marking on the cable — the cable, the drum label and the documentation must show the manufacturer, product designation, standard, Euroclass classification, conformity mark and notified body number.
5. Retention — the responsible person under CDM 2015 / Building Regulations should retain DoPs for installed cable as part of the building's health and safety file, especially in HRBs under the Building Safety Act 2022.

A common question on EICR work in older buildings is how to code cable that pre-dates the CPR or sits below the class now expected for the location. The right answer is rarely "code everything C2" — apply the standard EICR coding framework to the actual risk in the actual location.

Buying Cca cable in the UK is straightforward but requires discipline. Wholesalers stock multiple brands and grades; the same headline "twin and earth" or "SWA" descriptor can map to several Euroclass results depending on manufacturer and construction. The cable on the shelf is rarely labelled with a giant "Cca-s1b,d1,a1" sticker — it is labelled with a part number that maps to a DoP.

1. Specify the Euroclass on the order — "1.5mm² twin and earth, BS EN 50525 / BS 6004 equivalent, Cca-s1b,d1,a1" — not just "1.5mm² T&E".
2. Ask the wholesaler for the DoP at the point of order. Most major UK manufacturers publish DoPs on their websites under the product code.
3. Verify on delivery — check the drum label and the cable surface marking match the DoP. The Euroclass code should be printed or stamped on the sheath at the standard interval (typically every metre).
4. Photograph the drum label and the cable marking before installation. Store the photographs and the DoP in the project records.
5. Retain the DoP in the building's O&M manual / golden thread (for HRBs) so that the inspector, the Responsible Person and any future contractor can trace the installed cable back to its declared performance.