Jane Embury looks at what fire is and why it must be contained
The International Association of Fire and Rescue Services (CTIF) collects fire data from countries and cities worldwide.
CTIF says that over 100,000 people are killed by fire every year. That makes it among the most common causes of death for children and young adults.
Most fatal fires occur in the home. In developing countries that may be because of open cooking fires. In more developed countries, an electrical fault or a dropped cigarette.
It’s why developed, and most developing countries, have fire regulations that should minimise fire risk. However, understandably, poorer countries find it harder to police those regulations.
It also requires 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.
This molecular energy is then transferred to other fuel and oxygen molecules to create and sustain the chain reaction.
Taming fire generally involves the removal of heat, in most cases using water to soak up heat. Without energy in the form of heat, the fire cannot heat unburned fuel to ignition temperature. The fire will eventually go out.
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 and fire doors, should contain the fire in one discrete area. They should also provide escape routes for the building’s occupants and safe entry for fire fighters.
The fact is that most fires start with only a minimum of danger. A dropped cigarette, a spark from a faulty wire. If dealt with quickly or adequately contained, they pose no real threat.
However, an unchecked fire can spread with devastating speed, particularly in a large open space. And when it does get out of control, the best means of survival is escape.
Designing in safety is nothing new, and assessing risk is the starting point. In particular the need to build in compartmentation throughout the building. And 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. But put the right glass into the wrong frame, or vice versa, and you could be turning 60 minutes of fire-resistance into five minutes. In an evacuation situation, getting the design wrong at the outset could be a deadly mistake.
Evacuation is further complicated by the length of time it takes for people to leave a building. Many occupants won’t take the fire alarm seriously, particularly if false alarms have sounded before. This period – known as “start-up time” – is lengthened if occupants can’t see any visible evidence of a fire. A fire alarm, in itself, isn’t always alarming.
That’s a worry for us at Wrightstyle, because we know of fire resistance specifications being changed by the developer from 60 to 30 minutes. Or from integrity and insulation to integrity only, to stop fire but not radiant heat, simply for cost reasons.
At Wrightstyle, we have advanced glazing systems that provide protection for up to 120 minutes. It’s why our internal and external glazing systems have been specified on projects from the USA to Beirut to Hong Kong.
Importantly, we know all about fire and building safety. We therefore know that in larger buildings – particularly where there may be people with mobility issues, cutting costs could be a tragic compromise.