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Letter to the Editor

We present a letter from Frank Smith of FS Consulting, clearing up an inaccuracy in a previous Wiring Matters article.

"Mr Cameron Fraser

The Editor

Wiring Matters

The Institution of Engineering and Technology


20 July 2022


Dear Sir

I read with interest the article in May’s Wiring Matters, and note with embarrassment the generous acknowledgement to my part (with others) in developing the new regulations regarding protected escape routes in Amendment 2 to BS 7671.

It is clearly beneficial to publicise the amendment and its rationale. Unfortunately the article contains an inaccuracy, which I would like to redress in this letter; especially as it may have exacerbated further the confusion I understand there to be amongst some electrical designers as to what is, and what is not, a protected escape route. 

The intent of the amendment was to make BS 7671 more consistent with fire safety design practice as set out in, for example, BS 9999 and BS 9991 and the guidance within Approved Document B to the England and Wales Building Regulations; by removing reference to the building complexity categories BD1 to BD4 in Appendix 5 of the pre-Amendment standard and replacing it with restrictions on cables in protected escape routes. 

To ensure safe means of escape in the event of fire, BS 9999 et al set limits on the distances that must be travelled before someone reaches a place of safety – either ultimate safety (ie the open air) or a place of relative safety – generally a staircase, but in some cases a lobby or corridor, which is protected from fire by fire-resisting and smoke-resisting construction.  It is these protected staircases, lobbies or corridors which are the protected escape routes defined in Amendment 2.

Such protected escape routes are critical to ensure safe escape in the case of fire and this is the reason they should not contain large quantities of combustibles, including cables.

Generally protection is required when escape routes are long because of the height of staircases, or the length of corridors.  But in hotels they are also required in bedroom corridors because of the additional risk of the occupants being likely to be asleep and unfamiliar with the building.  However the Wiring Matters article shows what could reasonably be inferred to be a hotel bedroom corridor as not being a protected escape route, whereas it should be.

It also suggests that protected escape routes should be drab and unadorned without decoration.  They can indeed be like that, and frequently are in hotels, but more often they are the normally used circulation spaces and can be properly decorated and carpeted.  The key is the protection by fire and smoke-resisting construction.

The requirement that only essential cabling associated with the escape route be actually inside the protected corridor, staircase or lobby does not prevent the designer following these routes with cable runs.  It just means that the cabling should be separated from the route by fire and smoke-resisting construction, such as a ceiling or other enclosure.

Since its publication there has been debate on the implementation of Amendment 2 and suggestions that it is over-restrictive, particularly in multi-staircase buildings, and should perhaps be refined and more focused.  It would have been helpful to have had this debate during the public consultation stage of the preparation of the amendment, yet regretfully that did not happen.  It is appreciated that hospitals and similar health care premises represent a special case – hence the sentence at the end of Note 1 to Regulation 422.2. 

There may well be scope for some fine tuning, but nevertheless it should be noted that the new Amendment 2 actually removes restrictions on cabling in unprotected escape routes for BD2 – BD4 buildings.  The old BS 7671 had quite stringent requirements on the types of cable that could be used in escape routes – protected or otherwise – in such premises.  Moreover, because of the vague definition of what an escape route is, virtually anywhere in a building could be construed to be an escape route.  Now these requirements have been removed except for protected escape routes.  So overall it is a case of swings or roundabouts, or win some, lose some – not an onerous ratcheting up of the regulations.

Yours sincerely



Frank Smith, MIFireE, CBEng
Fire Safety Engineering Consultant