FIRE SAFETY
British Standards BS8519:2010 and BS EN12485 clearly recognise underground public areas such as car parks, loading bays, and large basement storage as ‘Areas of Special Risk’, with the potential for fire temperatures well above the current requirements of the Building Regulations. In these environments more stringent requirements for fire resistance may be needed, particularly for any wiring systems that enable operation of life safety equipment that are routed through them.
An even worse scenario Almost all life safety and firefighting systems depend on the reliable function of electric cables during emergency. If these essential cables fail during a fire event, the critical equipment they enable also fails. This could mean that firemen’s lifts, fire sprinklers, hydrant pumps, smoke and heat extraction equipment and pressurisation fans, emergency communication, alarms, and lighting systems, stop working during evacuation, putting occupants, emergency response workers, and property, at risk. It is therefore concerning that the only exception in the UK Building Regulations for fire resistance testing to BS476 parts 20-24 (which may already be obsolete for many buildings) is for the very electric cables required to power all emergency life safety and firefighting systems. This contradiction allows these essential cables to be tested to alternative flame tests, which have little or no relevance to real building fires, and at even lower final temperatures than required for all other fire-resistant elements of the building.
A ‘testing anomaly’
This testing anomaly has occurred in the UK Building Regulations because British Standards testing protocols for fire- resistant electric cables adopted by the Building Regulations (Protected Circuits) allow this shocking exception. It is interesting to note that other developed countries, including America, Canada, Australia, New Zealand, Germany, and Belgium, have, for years, required testing of these essential cables to the same fire time temperature protocol as every other building element, which is the same as used in BS476 parts 20-24, i.e. ISO 834-1/ EN 1363-1.
Today we have a much wider range of built environments, so adopting a ‘one size fits all’ protocol for fire resistance testing of wiring systems may no longer be appropriate. Clearly economic factors must also come into play and, as it stands, many of our current products and test regimes – including those for electric cables – may provide an adequate level of protection in small or low-rise buildings where evacuation times are short. The concern is: Are these same products and
28 Health Estate Journal August 2018
MICC’s mineral-insulated fire survival wiring is being extensively used in a new refuge shelter at Kuwait University.
standards going to provide the required reliability in performance and duration for the new large high-rise and mega projects, and especially large healthcare facilities, where long evacuation times and secure ‘protect in place’ refuges are unavoidable?
Beyond the Regulations It is correct to say all British Standards, and indeed the Building Regulations themselves, are only minimum requirements, so while it is often mandatory to meet these minimum codes, it does not preclude the design of buildings and systems with higher performances. The professional engineers who design our buildings and systems are accountable for the use of ‘reasonable skill and care’ in design, but the ‘fit-for- purpose’ criteria often remain the
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Almost all life safety and firefighting systems depend on the reliable function of electric cables during emergency
responsibility of the building owners or/and the installing contractor where the ‘purpose’ was reasonably known. It has been a surprise to some building owners and installing contractors to find out that simply following the professional consultants’ specifications may not absolve them from liability if it was reasonably known that a higher performance than the minimum code was required.4
Looking at global best practice for fire resistance testing of electrical wiring systems enabling life safety and firefighting systems, the American UL 2196 test method is more relevant. This test is undertaken in a large representative 6.6 m by 7.0 m vertical furnace, where cables, fixings, and accessories, are all tested together in the mounting configuration they will be actually installed. The most demanding installation configuration is for vertical runs of cables, a common and unavoidable installation condition for all tall buildings. UL2196 requires that cables are tested at their rated voltage, and with a minimum five samples, across a range of small to large sizes. All these circuits are mounted both horizontally and vertically, in 3 m (10 ft) lengths, with bends and joints if needed. The cables are energised,
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