Fire Resistance Standards and my duty to design with appropriate skill and care
“What if I became aware that parts of the very building regulations I rely on are inadequate?”…
In light of recent major fire events in the UK and around the world, having British Standards years behind global best practice for electrical wiring systems enabling life safety and firefighting systems is unacceptable. Fortunately there is expertise and wiring systems both approved and available in the UK market to assist you.
In today’s day and age, our metropolitan cities are ever expanding. With space constrictions we are building taller, and deeper than ever before. However with the changes in society and construction economic demands the regulations and standards which our lives depend on have not kept up to date.
Almost all Life Safety & Fire Fighting 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 & heat extraction and pressurization 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 Building Regulations for fire resistance testing to BS476 pts 20-24 is for the very electric cables required to power all emergency life support 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 lower final temperatures than required for all other fire resistant elements of the building.
This is a risk we take on a daily basis with the polymeric fire retardant cables that we install across all types of construction projects. Due to the lack of adequate fire testing standards and weak building regulations in the UK there is no guarantee of performance in a realistic fire conditions available to building designers.
What is can be overlooked is when installing kilometres of plastic polymer based cables the material that makes up the cable insulation and jacketing may in fact represent the largest fixed fuel source in the building. The polymeric cable can actually burn in two ways, either externally from a direct flame, or by internal heat, via an overload or a short circuit (often due to the cable being damaged unnoticed on installation). For a fire to start and spread there are three basic requirements… polymeric cables provide all 3!
- Fuel Source – the plastic polymer based materials in the cable construction
- Oxygen – the air in and around the cable
- Ignition source – a spark from outside the cable or a short circuit inside
Fires are not even the prime cause of human fatalities, smoke in fact is the largest contributor to death. When investigating the heat release to oxygen consumption, petrol produces 48 mega joules, PE and XPLE, (which many cable manufacturers must use as the insulation to meet low market price expectations), produces nearly as much energy as petrol at 46 mega joules. Not only does this heating of cable burn up the oxygen reducing the amount of breathable air in the atmosphere it in fact produces carbon monoxide. It is proven that 95% of deaths in a fire are from carbon monoxide poisoning.
Mineral insulated cable, commonly referred to as MICC or Pyro cable, is the original fire proof cable technology. It is made of a copper sheath rather than a Polymer base product, is inorganic. Bare MICC / Pyro cables when brunt produces 0 mega joules of energy. They will not start a fire and certainly will not make one worse.
Historically MICC / MI cable was the only fire survival wiring system in the World. It has been thoroughly tested with many installations still in operation since the 1930s. The UK English heritage organisation give MICC fire survival cables a 120 year life expectancy before considering routine replacement. In comparison polymeric cables generally only give around 10 years of active operating performance at their rated current, with the performance degrading year on year from installation, further risking the lives of the building occupants. Cables running at full load in moderate to high ambient temperatures can become a fire risk after only 2/3 years of operation.
Whilst it is common to rely on code alone, professional consultants are generally indemnified from designing with a ‘fit for purpose’ mandate, it remains necessary to exercise ‘reasonable skill and care’. Even if the builder and/or project owners inherit more liability under the Sale of Goods Act (5) due to implied terms that the goods and products supplied will be of satisfactory quality where a purchaser makes known a particular purpose (4), there remains both an ethical and prudent incentive for the contracted professional consultant to factor in the design any known limitations in regulation or standards.
BRAC (Building Regulation Advisory Committee) is aware of the Protect Circuit testing anomaly and hopefully will address this in future revisions.
Fortunately there is expertise and wiring systems both approved and available in the UK market to assist electrical design engineers find appropriate solutions for all major projects where egress times are long or anticipated fire profiles could be in excess of the minimum regulatory requirements of today. The MICC Ltd company based in Washington, Tyne & Wear, UK, is one such manufacturer who produces essential wiring systems for Protected Circuits for the most demanding applications in buildings, underground built environments, nuclear power and industrial Petro Chemical applications.
For more information please visit our website via the below link;
Office: +44 (0)191 416 8884
Office and Factory Address:
Temperature House, Unit 21 Sedling Road, Wear East Industrial Estate, Washington, Tyne and Wear.
United Kingdom. NE38 9BZ