Cause for alarm
Our industry expert explains why it’s vital for electrical contractors to ensure that wiring systems are adequately supported in the event of a fire
After several tragic fire incidents, and following discussions with the Fire and Rescue Service, Regulation 521.11.201 (AMD 3 BS 7671: 2008) was introduced, its purpose being to limit the risk to firefighters entering or leaving a premises from entanglement by cables.
Subsequently, there has been much confusion and discussion within the electrical installation industry relating to how this should be applied to premature collapse of wiring systems in escape routes. To add to this confusion, other fire safety standards, such as BS 5266-1 (emergency lighting) and BS 5839-1 (fire detection and fire alarm systems), recommend the methods of cable support should be non-combustible and such that circuit integrity is not reduced below that afforded by the cable used, while maintaining adequate support.
This article considers the development of Regulation 521.11.201/521.10.202 and whether premature collapse is a term that provides the necessary clarity of understanding when considering the requirement in parallel with other fire safety standards, e.g. clause 26.2f of BS 5839-1.
Escape routes and BS 7671
The confusion inherent in the original regulation related to “escape route”. How should escape route be defined?
The definition used in BS 7671 for escape routes was different to that used in other guides, regulations and legislation:
BS 7671: “Path to follow for access to a safe area in the event of an emergency.”
Building standards technical handbook: “A route by which a person may reach a place of safety.”
Approved Document B in England and Wales: “That part which a person has to traverse before reaching either the safety of a final exit or the comparative safety of a protected escape route.”
To add further confusion, there is also a definition for a “protected” escape route.
Industry confusion, and the fact that firefighters may enter and leave premises by ways other than defined escape routes, meant that in a subsequent standard Regulation 521.11.201 required amending.
To this end, the regulation was amended to delete the reference to escape route and renumbered 521.10.202 in BS 7671: 2018. The removal of escape routes means that the regulation now applies to all areas of the installation.
Fire safety standards
It has long been recognised that cables forming part of a critical signal path, such as fire detection and fire alarm systems (BS 5839-1 and 6), emergency lighting systems (BS 5266-1) and systems for life safety, firefighting etc (BS 8519) require continuing functionality during a fire.
For example, clause 7.3 of BS 8519 states: “The life safety, fire-fighting and other critical system cables should be installed on a dedicated cable support system… and designed to maintain its circuit integrity when exposed to fire conditions for at least the survival time in clause 5.”
Clause 5 in BS 8519 gives minimum cable categories that relate to minimum fire survival times. This standard also references the fire survival time for cable support systems in clause 17. These recommendations are similar to those found in the BS 5839 series and BS 5266-1 for critical signal paths.
The purpose of recommending minimum fire survival times is to ensure that the necessary fire safety systems continue to function during a fire. However, Regulation 521.10.202 of BS 7671 does NOT relate to the maintenance of any critical signal path.
There is an argument for the application of such minimum fire survival times to systems other than fire safety systems, however it seems clear that other currently unforeseen issues would likely arise.
Premature collapse
There is no specific definition of premature collapse to be found in Part 2 of BS 7671. One dictionary definition of premature is, “occurring or done before the usual or proper time; too early”. This plain meaning of premature is reasonable.
Since the purpose of Regulation 521.10.202 is not to maintain the critical signal path, rather to limit the risk to firefighters, premature collapse should be considered in relation to that single purpose.
Electrical contractors, network installers and the like are not expected, or qualified, to judge how fires behave, the likely temperatures that will be attained, nor how firefighters will carry out their role within a premises that is on fire.
It is important, therefore, that electrical contractors and other installers give due consideration to the support given to wiring systems to provide maximum reasonable application of Regulation 521.10.202.
Such an approach places a great deal of responsibility on contractors to apply the regulation, not because they want to meet the minimum expectation vis-à-vis wiring systems, screws, wall plugs, etc, but rather because they want to protect firefighters who are working under extremely dangerous conditions.
In practice therefore, an electrical contractor should consider, as a minimum, the following:
Wall fixings – current industry guidance is that plastic wall plugs remain suitable for use. Careful consideration should be given to the mass of the wiring system that is to be supported (including the trunking, cable tray, etc with the cables in situ). Will the structure of the building maintain sufficient fire resistance to permit cables to avoid the need for metallic supports? Will such supports be sufficient if firefighters damage ceilings when applying water?
Cable clips – metallic clips are essential as indicated by Note 3 and 4 of Regulation 521.10.202
Brackets or internal clips for PVC trunking – to keep the lid or cables in place (see Note 3 of Regulation 521.10.202).
Conclusion
There are two reasons why wiring systems are to be supported adequately in the event of a fire:
To maintain the critical signal path for fire safety systems
To limit the risk of firefighters becoming entangled during a fire.
Regulation 521.10.202 applies to the second of these only. Reference should be made to the relevant fire safety standards when considering the maintenance of the critical signal path.
Electrical contractors should carefully consider their responsibilities when installing wiring systems. Under fire conditions, failure to make the right choices may lead to serious consequences.
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Tim Benstead is the former Principal Technical Author of the NICEIC, a member of JPEL64, Chair of JPEL64/B and a member of FSH12/1, the BSI committee responsible for BS 5839-1 and BS 5839-6 for 15 years. He writes with authority and understands the concerns of the contractor and those responsible for domestic premises.
