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BS9991:2024 - Section 27.2.2 - Services running horizontally

John Samways

An updated version of BS9991 has been published on 27th November 2024. The new BS9991:2024 includes requirements for services running horizontally within common access corridors.

Section 27.2.2 states: 

Where services are run horizontally within common access corridors and lobbies, including corridor access for firefighting shafts, they should be either enclosed with fire-resisting construction or meet all of the following criteria: 

a) The exposed surface of the material/product used is class B-s3,d2 or better;

b) The supports and fixings in the cavity are class A1;

c) any pipe insulation system is class B-s3,d2 or better; and

d) any electrical wiring in the cavity is laid in metal trays or metal conduit. 

From an electrical perspective the items requiring compliance are a,b and d.

b and d are simple to comply with however item a appears to be very difficult given the cable products commercially available.

 

The following services are available as B2ca - Cat6 data cables, Optical cables, co-axial TV cables, SWA cables.

Flat twin (FT&E) cables in LSOH form only appear to accord to Dca.  There doesn't seem to be flex cables that are better than Dca either. So we can use steel conduit to wire all the small power and lighting in the common corridors, this is quite a price hike. However, wiring from the conduit system to the luminaires in flexible cable doesn't appear possible. 

A further complication is that fire rated cables such as FP200 or FP600 are not currently covered by the CPR Euro class rating. Therefore we do not know if they will accord to B2ca or better. 

I have spoken with Prysmian cables, and there were not able to provide me with details of any cables suitable for wiring small power or lighting that would accord with B2ca or better. 

I would be very interested to hear from fellow engineers, their point of view on the new BS9991:2024 and how to comply with the new requirements. 

  • Hi John,

    Been struggling with the same issue, and updated this post a couple of times now.

    These Bca cables are much less abundant and much more expensive than there non-CPR classified alternatives, especially the power cables.  Either, adopting a metallic trunking and conduit system or construction of a fire resisting enclosure; would appear to be the only alternatives.

    The British Standard used for the assessment of cables under the Construction Products Regulation (CPR) is BS EN 50575 which refers to BS EN 50399, among others.  I had erroneously assumed BS 60332-3 (referred to in BS 7671 422.2.1 for cables in the scenario described) was a more onerous test.  I am now aware that the flame testing employed by BS 50399 is much more onerous than both BS EN 60332.1.2 and BS EN 60332-3.

    As you mention, all cables are now required to be classified under the CPR, however; this appears to exclude 'fire resistant' cables which makes assessment of there suitability under CPR difficult.

    -

    In answer to your original query regards complying with BS 9991, the standard is clearly attempting to create a fire sterile environment by adopting materials with zero or low combustibility.  In this vein, a class Cca or lower cable has been deemed to present an avoidable risk for flame propagation.

    Since fire resistant cables are presently excluded from the CPR Class system could this be interpreted to mean that any 'fire resistant' cable could be deemed of equivalent safety as a CPR Bca cable? I'm already doubting this possibility since fire rated cables are typically tested to BS EN 60332-3 making no mention of compliance to BS EN 50399.  You might have a hard time substantiating this.

    Its a frustrating one and any departure from the standard would need to be acknowledged and approved by client, fire engineer, insure etc.

    Let me know if you have made any head way on this.

  • Interesting article by Eland Cable relating to the relevance of cables and BS 9991.  In summary they argue non fire resisting cables are not considered by BS 9991:2024.

    www.elandcables.com/.../bs9991-does-the-new-regulation-affect-electrical-cables

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