Curtain wall is a term used to describe a building façade which does not carry any dead load from the building other than its own dead load. These loads are transferred to the main building structure through connections at floors or columns of the building. A curtain wall is designed to resist air and water infiltration, wind forces acting on the building, seismic forces, and its own dead load forces.
There are over 300 high-rise buildings in Fairfax County and with new development around future metro stations, there are many more planned. the vast majority of our highrises are built using curtain wall construction.
The first alarm assignment on a high-rise fire is designed to cover the first essential positions with the understanding that a confirmed fire will get at least a 2nd alarm.
The 4th due engine and the 2nd due truck on the 1st alarm are assigned to go to the floor above the fire. Discuss the tactics expected of these two units and why knowing the location of the fire on the fire floor is important to the operations on the floor above as it relates to curtain wall construction. Discuss also just what a curtain wall really is, how the exterior walls are attached, how fire can extend, and where checking for extension needs to occur.
(Courtesy of Deputy Fire Chief Jeff Coffman)
1 comment:
I like to think of the curtain wall as a veneer (like brick or stone, etc.). It holds up its own weight and is usually attached to the building structure by hooks and or bolts and welds.
Each portion of the curtain is like a panel, installed one at a time. The panels can vary in size, are usually quite heavy, and can be made from a variety of materials (i.e., glass, masonry, foam and stucco combinations, etc.).
The connections on each panel are vulnerable, as they are usually metal and exposed, making them susceptible to heat and flame impingement. When the panels are put in place, there is usually an air gap that runs the full length and height of each panel, which means heat/smoke/fire, can travel in all directions. Crews working above will have to be alert to the location of the fire because they will likely encounter heat, smoke, and fire, which may be remote from the actual area of the fire. First in companies have to be careful to identify the fire floor. The early conditions, which may not be clear, may cause confusion and companies getting sucked into smoke on one floor may be missing something below. Smoke and fire spread can be rapid as the air gap between the panels and the structural skeleton allow air movement. Units working above must check all locations of the floor above and all floors from the roof down to ensure fire and smoke extension is in check. Critical interior locations will be areas following the outside walls. We must check the area from baseboard to plenum space and everything in between on each floor. Since fire, heat, and smoke can run in between the structure and the curtain walls, not only are the joint connections susceptible, but also the structural components will be exposed, causing the potential for structural movement and potential interior or exterior collapse. As well, the curtains themselves can become so exposed that they could actually begin to lose their stability and fall.
Don't forget about carbon monoxide gas being generated and being found in lethal concentrations remote from the fire.
Here is another good example at how construction technology complicates our job further and how we need to always be on our toes and asking questions to seek answers that help us understand and prepare better.
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