Annex 2.B Reaction to fire
The performance criteria in terms of reaction to fire can be satisfied by the European Harmonised fire tests. BS EN 13501-1: 2018 provides the fire classification procedure for all construction products in terms of their reaction to fire.
For all construction products, the consideration is of a fire, initiated in a room, which can grow and eventually reach flashover. This scenario includes three fire situations corresponding to three stages in the development of a fire:
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the first stage includes initiation of the fire by ignition of a product, with a small flame, on a limited area of a product,
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the second stage addresses fire growth eventually reaching flashover. It is simulated by a single burning item in a corner of the room, creating a heat flux on adjacent surfaces. For floorings, fire is seen to grow in the room of origin, creating a heat flux on the floorings in an adjacent room or corridor, through a door opening, and
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in the post-flashover phase all combustible products contribute to the fire load.
External wall cladding systems - Currently, there is no recognised European Harmonised fire test for facades or construction products exposed to a fire in a cavity. Therefore, the reaction to fire classification system in BS EN 13501-1: 2018 for external wall cladding systems has been adopted. It is important to understand the limitations of these tests and their intended field of application. For example, some tests are material or single component tests only and the single burning item (SBI) test is designed for internal linings. The SBI test can include the mounting technique used in its end-use application including any air gaps or substrate (see clause 2.B.2).
Even if an external wall cladding system is constructed of materials achieving European Classification A1 and A2, clients may wish to further assess the cladding system against the performance criteria in ‘Fire performance of external thermal insulation for walls of multi-storey buildings’ (BR 135, 2013) when tested in accordance with BS 8414-1: 2020 or BS 8414-2:2020. BS 9414: 2019 provides additional information on the application of results from BS 8414 tests. This large scale facade test may be used as an alternative to European Classification A1 or A2 where the external wall cladding system of a domestic building is less than 1m to the boundary and the building has no storey at a height of 11m or more above the ground.
The local authority verifier must notify the Building Standards Division where any proposal is supported by BS 8414 fire tests and BR 135 classification reports. Rigorous compliance checking of the design and construction must be undertaken and evidence recorded.
A list of exemptions to European Classification A1 and A2 components that form part of a non-loadbearing external wall cladding system is provided below:
- cavity trays
- cavity vents
- any part of a roof (other than a part of a roof pitched at an angle of 70º or more to the horizontal) if that part is connected to an external wall
- door frames and doors
- insulation and water proofing materials used below ground level and up to 300 mm above ground level
- intumescent and fire-stopping materials, fire barriers and cavity barriers where the inclusion of the materials is necessary for compliance with the standards in Section 2 (Fire)
- membranes
- seals, gaskets, fixings, sealants and backer rods
- thermal break materials, and
- window frames and glass.
Notes:
[1] Window frames and glass includes glazed curtain walls or glazing to balconies which should retain any combustible interlayers in the event of a fire.
[2] See clause 2.7.1 for guidance on service penetrations.
Non-combustibility test (EN ISO 1182) identifies products that will not, or not significantly, contribute to a fire, regardless of their end use. The assumption is that products classified as A1 make no contribution to fire growth or to the fully developed fire. A product classified as A1 is assumed to present no smoke hazard.
The European Commission has drawn up a list of products which, under specified conditions, can be considered to be class A1 without testing. This information is given in the Commission Decision 96/603/EC (OJ L 267 19.10.1966 p23) as amended by 2000/605/EC (OJ L 258 12.10.2000 p36) and 2003/424/EC (OJ L 144 12.6.2003 p9).
Heat of combustion test (EN ISO 1716) determines the potential maximum total heat release of a product when completely burning, regardless of its end use.
Single burning item test (EN 13823) evaluates the potential contribution of a product to the development of a fire, under a fire situation simulating a single burning item in a room corner near to that product. When a classification includes “s3, d2” this means that there is no limit set for smoke production and/or flaming droplets/particles.
Ignitability test (EN ISO 11925-2) evaluates the ignitability of a product under exposure to a small flame.
Reaction to fire relates to the degree to which a product will contribute, by its own decomposition, to a fire under specified conditions. Products are classified as A1, A2, B, C, D, E or F (with class A1 being the highest performance and F being the lowest) in accordance with BS EN 13501-1: 2018. Class F is assigned when a product fails to attain Class E. Untested products cannot be classified in accordance with BS EN 13501-1: 2018.
The classes of reaction to fire performance of A2, B, C and D are accompanied by additional classifications related to the production of smoke (s1, s2, s3), with s1 indicating the lowest production, and/or flaming droplets/particles (d0, d1, d2), with d0 indicating the lowest production. Classes E and F include flaming droplets/particles only as shown in Table 2.10 below.
When a classification (other than as specified in Regulation 8) in this Technical Handbook refers to Class A2, B, C and D the sub-indices are deemed to include s3, d2 which means there is no limit set for smoke production and/or flaming droplets/particles.
Table 2.10 Reaction to Fire
| European Classification [1] | Fire Test | Additional Classification |
|---|---|---|
| A1 |
BS EN ISO: 1182: 2020 and BS EN ISO: 1716: 2018 or Products made from only 1 or more of the materials considered as Class A1 without the need for testing, as defined in Commission Decision 96/603/EC of 4th October 1996 establishing the list of products belonging to Class A1 “No contribution to fire” provided for in the Decision 94/611/EC implementing Article 20 of the Council Directive 89/106/ EEC on the construction products. None of the materials contain more than 1.0% by weight or volume (whichever is the lower) of homogeneously distributed organic material. |
None |
| A2 | BS EN ISO: 1182: 2020 or BS EN: ISO 1716: 2018 and BS EN 13823: 2020 | Smoke production and flaming droplets / particles |
| B, C and D | BS EN: 13823: 2020 and BS EN ISO: 11925-2: 2020 | Smoke production and flaming droplets / particles |
| E | BS EN ISO: 11925-2: 2020. | Flaming droplets / particles |
There is a procedure by which certain products can be assigned a particular fire classification without the need for testing. Such products have well established reaction to fire performance and have been agreed by the Standing Committee on Construction. Agreements relating to such products which may be ‘classified without testing’ (CWT) are published in the Official Journal of the European Commission and are listed on the Nando-CPD database on the EC website.
European Classification A1 in Table 2.10 includes a list of products drawn up by the European Commission which, under specified conditions, can be considered to be Class A1 without testing. This information is given in the Commission Decision 96/603/EC (OJ L 267 19.10.1996 p23) as amended by 2000/605/EC (OJ L 258 12.10.2000 p36) and 2003/424/EC (OJ L 144 12.6.2003 p9).