The application of Regulation 422.2.1 of BS 7671

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The application of Regulation 422.2.1 of BS 7671

In response to the number of enquires received by NICEIC and ELECSA Technical Helplines, this article seeks to clarify the application of Regulation 422.2.1 (Conditions for evacuation in an emergency) of BS 7671 and the associated Regulation 521.11.201 (Wiring systems in escape routes).

To assist contractors in determining which locations in a building the requirements of Regulation 521.11.201 can apply to, the article ‘What constitutes an escape route’, contained in this issue of Connections provides guidance.

Regulation 521.11.201 was introduced into Amendment 3 of BS 7671: 2008 to ensure wiring systems in escape routes are so supported that they will not be liable to premature collapse when subjected to the eff ects from fi re. This requirement is to minimise the risk of wiring systems hindering building users evacuating the building and fi refi ghters entering the building to carry out their duties, such as search and rescue, and it applies to all buildings, including buildings used for domestic purposes.

Regulation 521.11.201 also refers to the requirements of Regulation 422.2.1 to be applied, ‘irrespective of the classifi cation of the conditions for evacuation’, and that requirement has been the catalyst for the number of enquires received by NICEIC and ELECSA; contractors have been enquiring whether the enhanced wiring system requirements detailed in Regulation 422.2.1 apply to buildings used for individual dwellings? 1 To answer such a question an overview of Regulation 422.2.1 follows.

Overview of Regulation 422.2.1

Escape routes are intended to give building users a low risk means of evacuation during an emergency, such as an outbreak of fi re, and the intention of Regulation 422.2.1 is to maintain this low risk by requiring wiring systems not to be installed in escape routes unless they are enhanced wiring systems.

The time to complete evacuation of a building following an outbreak of fi re is an important factor to determine the application of Regulation Group 422. Time to complete evacuation will typically have a correlation with one or more of the following: • number of storeys, • fl oor dimensions and shape, • number of individual rooms/areas. • number and characteristics of building users.

Regulation 422.2.1 therefore applies to buildings characterised by prolonged escape routes and/or a large number of building users, and such buildings posing an increased risk to persons at times of evacuation are given condition codes BD2, BD3 and BD4 (see Appendix 5 in BS 7671). BS 7671 gives no guidance on what constitutes an easy or diffi cult exit or high and low density occupation. Such judgements would be for the designer to consider.

1 For the purpose of this article a dwelling is an individual house, bungalow or maisonette. Domestic premises

It is highly unlikely that the enhanced wiring system requirements of Regulation 422.2.1 would be applicable to buildings used as individual dwellings. Dwellings (typically classed as BD1), especially those having two or less storeys, normally do not have prolonged evacuation times, due to ease of exit (the occupants are normally familiar with the points for egress) and low occupancy dwellings, therefore, impose a low risk on persons evacuating.

Some dwellings may have a prolonged evacuation time, such as a dwelling with a fl oor more than 4.5 m above ground level. To meet building regulations such dwellings are required to have additional provisions to provide a safe means of escape. The options suggested by Approved Document B (ADB) for England and Wales are: • a protected stairway either extending to a fi nal escape route or giving access to at least two escape routes at ground level each giving access to fi nal exits, • top storey separated from lower storeys by fi reresisting construction and be provided with an alternative escape route

It is to such ‘protected’ areas that the requirements of Regulation 422.2.1 apply. In such locations, wiring systems are not to be within arm’s reach unless they are protected against mechanical damage and are to be as short as possible. Furthermore, wiring systems are to be non-fl ame propagating, limiting options in the type and range of cables and systems to be used.

Fig 1 Regulation 422.2.1 normally does

not apply to individual dwellings

(a)

The requirements of Regulation 422.2.1 may, therefore, be applicable to escape routes of buildings containing individual units of domestic accommodation, for example, a block of fl ats, but not to typical single-user dwellings having a maximum of two storeys. High-rise blocks of fl ats can be classifi ed as BD2 where it is identifi ed that the number of storeys and/or number of fl ats on each storey have an increased risk due to a prolonged evacuation time.

It is worth noting that, regardless of the enhanced wiring system requirements of Regulation 422.2.1, Clause 16 (Wiring) of BS 5839-6 the British Standard for fi re detection and fi re alarm systems in individual dwellings requires fi re systems to Grade A and Grade B to incorporate fi reresisting cables. This requirement supplements the requirements of BS 7671. Summary

For the reasons given within this article, it is the view of NICEIC and ELECSA that the link to Regulation 422.2.1 given in Regulation 521.11.201 is there to remind the designer that the requirements of Regulation 422.2.1 apply to ‘protected escape routes’ rather than general escape routes.

The requirement for robust supports to wiring systems given in Regulation 521.11.201 is applicable to wiring systems in all types of escape routes in buildings irrespective of the conditions coded in Regulation 422.2.1, rather than wiring systems in individual dwellings having to be enhanced to meet the requirements of Regulation 422.2.1.