Steel Appeal – Fire Dynamics
Taming fire generally involves the removal of heat, writes Jane Embury, our marketing director.
In most cases that means dousing it with water.
That water, of course, comes from either the building’s own sprinkler system or the fire service.
Without energy in the form of heat, the fire cannot heat unburned fuel to ignition temperature. In addition, water acts to smother the flames and suffocate the fire.
But what is also needed is containment – to prevent the fire spreading from its original location. Those protective barriers, often external curtain walling or internal glass screens, should also provide escape routes.
That’s where fire resistant glass and glazing systems are so important, because modern steel systems are technically advanced. Simply, 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. It 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. Cold water from a sprinkler system can cause the glass to break, allowing more oxygen to the seat of the fire.
As a fire escalates, due to thermal expansion, flammable gases are able to pass through relatively small holes and gaps in ducts and walls. Heat can also be transmitted through internal walls by conduction.
Heat transfer can also cause fire to spread from its original location.
Most fires start with only a minimum of real danger – a dropped cigarette, or a spark from a faulty wire.
However, an unchecked fire can spread with devastating speed. That’s particularly so 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. These range from power failure to cyber-attack, from civil disorder to fire and explosive detonation.
These help to create risk assessments that illuminate how that that building should be designed and built.
Designing in safety is nothing new. It 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.
Assessing risk is the starting point, and in particular the need to build in compartmentation throughout the building.
For the glazed components, that means analysing the level of containment the glass will provide. Also, its compatibility with its framing system.
Importantly, if you put the right glass into the wrong frame, you could be turning sixty minutes of fire-resistance into five minutes.
At Wrightstyle, we’ve come a long way to meet the evolving design requirements of architects and the increasing stringency of building and fire regulations.
Our two messages are simple: first, specify only glass and framing systems that have been tested together.
Second, when it comes to the best in fire safety, it has to be steel …. the steel appeal and fire dynamics.