Steel Appeal in Fire Safety – It is estimated that there are some 195,000 deaths each year from fire, and fire-related death ranks among the 15 most common causes of death for children and young adults. South-East Asia alone accounts for just over 50 percent of the total number of fire deaths worldwide.
Most, of course, are domestic fires. However, the human cost can be much greater when fire breaks out in a commercial building – particularly in countries that have either inadequate fire safety regulations or the means to stringently enforce them.
That was certainly the case in a fire a few years ago in a textile factory in Dhaka, Bangladesh. In that fire, men and women, most in their teens and early twenties, tried to escape down a narrow stairway barely 1.5 metres wide. In the ensuing stampede, seven women were trampled to death and fifty injured. However, what made this fire worse was that it was not an isolated incident. In November 2000, another 45 Bangladeshi garment workers were killed and 100 injured in a factory fire caused by an electrical short circuit. Among the victims were ten children. The stairwell was so crowded that workers broke windows and threw themselves out.
In 2001, 24 workers, mostly women, died in yet another factory fire in Dhaka, bringing the total number of lives lost in factory fires in the country to 84 in that one year alone. The tragedy, caused by faulty electrics, was again exacerbated by workers from several production units converging on the same escape stairway.
The Fire Challenge
The fire regulations on which building safety depend are themselves based on an understanding of fire dynamics – the fundamental relationship between fuel, oxygen and heat – the so-called fire triangle on which all fires, intentional or otherwise, depend. Get those three elements together and the fire triangle is joined by a fourth element – the chemical chain reaction that is actually the fire. In technical jargon, the triangle of combustion then becomes a tetrahedron.
It is a geometry that can either be friend or foe, as fuel and oxygen molecules gain energy and become active. This molecular energy is then transferred to other fuel and oxygen molecules to create and sustain the chain reaction. In an uncontrolled fire in a building, how it spreads of course depends on a whole range of factors – from the type of fuel (everything from ceiling tiles to furniture) to the building construction and ventilation.
Taming fire generally involves the removal of heat, in most cases using water to soak up heat generated by the fire. Without energy in the form of heat, the fire cannot heat unburned fuel to ignition temperature and the fire will eventually go out. In addition, water acts to smother the flames and suffocate the fire. But what is really needed is containment – to prevent the fire spreading from its original location. Those protective barriers, often external curtain walling or internal glass screens, must also provide escape routes for the building’s occupants – what was lacking in those fires in Bangladesh.
The Role of Fire-resistant Glazing
That is where fire resistant glass and glazing systems are so important, because modern steel systems are so technically advanced that they have overcome the limitations inherent in the glass itself.
The biggest limitation is that glass softens over a range of 500°C to 1500°C. To put that in perspective, a candle flame burns at between 800°C and 1200°C. In a typical flashover fire inside a building, temperatures can reach between 1000°C and 1400°C. These temperatures can disrupt the integrity of conventional panes of glass, which can crack and break because of thermal shock and temperature differentials across the exposed face. This will compromise the compartmentation of the building’s interior allowing fire to spread from room to room.
That can, incidentally, be a problem that a sprinkler system actually causes. There have been several notable cases where cold water from a sprinkler system has come into contact with heated non-fire rated glass, causing the glass to break and allowing more oxygen to the seat of the fire.
As a fire escalates, the amount of heat produced can grow quickly, spreading like a predator from one fuel source to another, devouring materials that, in turn, will produce gases that are both highly toxic and flammable. To make things worse, due to thermal expansion, these flammable gases are usually under pressure and able to pass through relatively small holes and gaps in ducts and walls, spreading the fire to other parts of the building. Heat will also be transmitted through internal walls by conduction.
As the fire worsens, and when unburned flammable gases reach auto ignition temperature, or are provided with an additional source of oxygen – for example, from a fractured window – an explosive effect called ‘flashover’ takes place. Flashover is the most feared phenomenon of any firefighter and signals several major changes in the fire and the response to it. First, it brings to an end all attempts at search and rescue in the area of the flashover. Simply, there will not be anybody alive to rescue.
Second, it signals that the fire has reached the end of its growth stage and that it is now fully developed as an inferno. That then signals a change in firefighting response because it marks the start of a worse danger – the risk of structural collapse. However, most fires, including the Bangladeshi examples, start with only a minimum of real danger – a dropped cigarette, a spark from a faulty wire – and, if dealt with quickly or adequately contained, pose no real threat.
The Global Landscape
The International Association for the Study of Insurance Economics (better known as the Geneva Association) says that – in the developed world – the cost of fire has reduced over the past decade from 0.28% to 0.16% of GDP, and the risk of dying in a fire has fallen from an average of 1.88 to 1.34 per 100,000 of population. However, that declining trend masks some stark variables, even between developed countries. For example, Hong Kong – with a densely-packed population of over five million people – has fewer fire fatalities than many of the largest cities in the USA. Or Singapore, with a fire death ratio of 2.3 per one million of population, can be compared with Japan, which has a ratio of 16.0 – a risk factor several times greater. The worldwide average is 10.7 per one million of population, a league table topped by Finland on 18.0.
The main lesson from the Bangladeshi fires is that fire can spread with devastating speed, particularly in a large open space such as a supermarket, open-plan office or factory. And when it does get out of control, the best means of survival is escape.
Around the world, more stringent building and fire regulations have led to architectural and design teams taking a multi-disciplinary approach to assessing hazards – from power failure to cyber attack, from civil disorder to fire and explosive detonation – and arriving at risk assessments that, hopefully, illuminate how that building should be designed and built.
Designing in safety is nothing new, and starts with actively assessing the possible risks against that building’s occupants, structure, resources and continuity of operations. There are a number of assessment methodologies to understand the potential threats, identify the assets to be protected, and how best to mitigate against those risks. That assessment then guides the design team in determining acceptable risks and the cost-effectiveness of the measures proposed.
HSBC Hong Kong
A good example is a recent project for HSBC Bank in Hong Kong, a commercially strategic HK$900 million financial data centre. This highly-sensitive building is HSBC’s main data hub for the Asia-Pacific region, processing financial transactions from banking operations across some 30 countries and territories and handling a variety of functions, including personal and business Internet banking, securities trading, credit card, treasury and global payments.
The design team had to create a building that would balance interior spaces filled with natural light with an exterior envelope able to withstand a spectrum of meteorological and man-made threats – everything from bomb attack to a typhoon. So secure is the finished building that it was the first data centre in Hong Kong to meet the industry’s most stringent reliability and security requirements, a reflection of the changing threat facing major companies and organisations, and the importance of protecting both the occupants of sensitive buildings and the integrity of their information systems.
Assessing risk is the starting point, and in particular the need to build in compartmentation throughout the building, examining the whole building’s capacity to withstand a fire or other threats. For the glazed components, that should mean analysing the level of containment the glass will provide and its compatibility with its framing systems, because the safety of the glass cannot be assessed without its framing system. Put the right glass into the wrong frame, and you could be turning sixty minutes of fire-resistance into five minutes. In an evacuation situation where seconds count, getting the design wrong at the outset could be a costly – and deadly – mistake.
There are many types of fire-resistant glasses currently on the market – and the ranges of products and sizes will continue to increase as the technology for combining glass and glazing systems develops. We have come a long way to meet the evolving design requirements of architects and the increasing stringency of building and fire regulations. Simply, the glass and framing technologies now on the market mean that the impossible is now possible.
Lee Coates leads research, development and worldwide testing at Wrightstyle Limited.
For further information, go to www.wrightstyle.co.uk
