What does the introduction of protected escape routes mean for cable routing and equipment in these areas? NAPIT’s Technical Events Manager, Paul Chaffers, examines the requirements following the publication of BS 7671:2018+A2:2022.
The latest update to the Wiring Regulations BS 7671:2018+A2:2022 includes significant updates to Section 422, which deals with ‘Precautions where particular risks of fire exist’.
New definitions have been introduced, with existing conditions for evacuation in an emergency deleted, so all in all, a lot to get our heads around.
Reasons for change
Before introducing the latest requirements of Regulation 422.2, I’ll explain why the existing Regulation required modification.
Previously, Regulation 422.2 referenced three conditions for evacuation in an emergency – BD2, BD3 and BD4 – and stated that the subsequent Regulations in Section 422 referred to these conditions, see Fig 1.
One of the challenges of using such conditions to determine if the relevant requirements of Section 422 apply, is finding out which condition is applicable to the building undergoing the work. After all, electrical designers aren’t fire engineers.
The other issue is that external influence BD1 was not included in the existing list of conditions, meaning that if you had a building type within this category, the requirements of Section 422 could be ignored.
BD1 conditions are for low density occupation with easy exit, and although the conditions are favourable for evacuation, it doesn’t necessarily mean such installations don’t require the extra measures given in Section 422 if there is a particular risk of fire associated with the building type or use. The Regulation was therefore flawed.
Protected escape routes
The newly-revised Regulation 422.2 introduces the concept of protected escape routes and requires:
Cables or other electrical equipment shall not be installed in a protected escape route unless part of:
- An essential fire safety or related safety system
- General needs lighting
- Socket-outlets provided for cleaning or maintenance
The requirements of this Regulation are very easy to understand, but perhaps the hard part is working out how we determine what a protected escape route is? We will start off by looking at the definition provided in BS 7671 Part 2.
BS 7671 Part 2 definitions
In order to understand the terms used, I’ve included the new definition for protected escape routes, as well as the standard escape route definition:
Protected escape route
A route enclosed with specified fire-resisting construction designated for escape to a place of safety in the event of an emergency (see also escape route).
Escape route
Path to follow for access to a safe area in the event of an emergency (see also protected escape routes).
A study of these definitions shows that there is a distinct difference between a protected escape route (with its special fire resisting properties) and a regular escape route. Therefore, if the building has been designed correctly, the correct means of escape should have been provided.
Means of escape
Simply put, the means of escape is the method provided within a building that allows safe escape to a place of safety, usually the open air.
In smaller buildings or buildings with a straightforward layout, this is carried out by reducing the distance needed to be travelled to exit the building. For this type of arrangement a regular escape route is usually all that is required, see Fig 2.
But for larger, more complicated buildings where longer distances have to be travelled, protected escape routes are used in order to protect escapees during evacuation. Protected escape routes are arranged with one or more of the following:
- Protected lobby
- Protected corridor
- Protected stairway
By design, these protected routes are fire and smoke-resisting but should also be fire sterile and preferably contain no combustible material. Think of a concrete staircase in a car park, and you will get the idea – see Fig 3.
So, what can be installed?
Well, actually very little; whilst general needs lighting and socket-outlets for cleaning or maintenance are permitted, care should be taken to avoid excess cabling within these areas.
Note 2 of Regulation 422.2 suggests that cables in protected escape routes should be limited to lighting and associated accessories, including emergency lighting and fire detection and alarm systems.
Depending on the fire safety strategy for the building, other alarm systems may be required and, therefore, suitable for inclusion within protected escape routes. Nuclear buildings and chemical plants are given as an example in BS 7671 Appendix 13 Escape routes and fire protection.
Cable choice
Wiring systems used for safety services are deemed suitable for protected escape routes, as referenced in Regulation 560.8.1, as follows:
- Mineral insulated cable systems complying with BS EN 60702-1 and BS EN 60702-2, and BS EN 60332-1-2
- Fire-resistant cables complying with IEC 60331-1, IEC 60331-2 or IEC 60331-3 and with BS EN 60332-1-2
- Fire-resistant cables complying with test requirements of BS EN 50200, BS 8434 or BS 8491, appropriate for the cable size and with BS EN 60332-1-2
- A wiring system maintaining the necessary fire and mechanical protection
Regulation 422.2.1 provides alternative solutions where cables with resistance to flame propagation according to the recommended requirements of the relevant part of BS EN 60332-3 series may be used, or where cables are contained in the following cable management systems meeting the recommended requirements of BS EN 60332-1-2:
- Non-flame propagating conduit systems to BS EN 61386
- Non-flame propagating cable trunking systems and cable ducting systems to BS EN 50085
Additionally, cables must have a minimum of 60% light transmittance when tested in accordance with BS EN 61034-2.
Conclusion
Fire safety in buildings can be complicated. Therefore, any proposed work that encroaches on a protected escape route should be approached with caution.
Discussions with the building owner or the person responsible for the building will be necessary as they should have details of the fire safety design of the building.
Where fire safety strategy plans or risk assessments are not available, expert fire safety advice should be obtained to identify any protected escape routes.
Where work is to be carried out, it is recommended that electrical designers and installers provide the responsible person with details of the electrical system and the maintenance requirements so this information can then be added to the fire safety manual.
Further information
As part of the launch of BS 7671:2018+A2:2022, all of NAPIT’s comprehensive collection of technical guidance books have been updated to give you the latest information.
Browse the technical guidance books range here
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