By Homer Robertson
Published Tuesday, February 1, 2011
| From the February 2011 Issue of FireRescue
Thanks to great fire service educators like Francis Brannigan and Vincent Dunn, we’re all a bit smarter about building collapse as it relates to fireground operations. Their books should be in the library of every fire station and required reading for serious fire service members who want to help their fellow crewmembers stay safe and survive.
Besides these great books, there are volumes of other well-written articles about building construction and collapse—in fact, it’s almost overwhelming to try to get your head around all of it.
For any drill to be effective, we have to take something we need to be better at, break it down into small pieces, and then train on those pieces. Accordingly, this month’s Quick Drill breaks down a few important points about collapse zones around a structure fire.
Every firefighter needs a good understanding of building construction and how fire affects it. If we’re talking about how far back to establish collapse zones, we also need to talk about how walls fall down.
An important teaching point: Different types of walls are affected differently based on the material used and the specifics of their construction. Examples: A freestanding wall has a higher potential for collapse than a non-load-bearing wall, while a precast tilt wall will normally fall at a 90-degree angle.
The bottom line: The first sign of possible collapse is the wall itself. Make sure your members can identify construction types, as well as other possible collapse warning signs, such as smoke and water coming from mortar joints, walls separating at the corners, or bowing walls.
3 Collapse Types
The three most common types of wall collapse are the 90-degree-angle collapse, the curtain-fall collapse and the inward/outward collapse. Each has its unique way of falling, but when establishing collapse zones around a building, always develop your zones based on the worst-case scenario.
The 90-degree-angle will fall similar to how a tree falls; the full height of the wall will separate from the building. Most collapse experts recommend a collapse zone distance equal to 1½ times the full height of the building for this type of collapse. The additional one-half is to protect firefighters from falling debris that may be projected out during the collapse. Remember: Bricks can weigh 4 to 6 lbs.
The horizontal length of the wall should also be considered when establishing a collapse zone where you suspect a 90-degree-angle collapse. Failure of one section can bring the entire length of the wall with it.
The curtain-fall collapse is like a curtain dropping, leaving a pile of debris at the base of the wall. It can fall both inward and outward.
The inward/outward collapse occurs when the wall begins to lean in either direction, forcing the lower section in the other direction.
Note: Although curtain-fall and inward/outward collapses may require smaller collapse zones, it’s best to prepare for the worst-case scenario and make all collapse zones 1½ times the wall height. In addition, any collapse zone should take into account not only the safe distance needed to avoid falling debris, but also radiant heat that’s often released after a collapse.
Collapse Zone Set-Up
Collapse zone set-up begins with the first-arriving apparatus. If the first-arriving company positions in a location outside the collapse zone, it will set the tone for later-arriving companies to do the same, and apparatus won’t have to be moved if conditions deteriorate or if the operation turns defensive.
We’re often aware of the dangers of building collapse when we’re involved in an offensive operation, but many of us tend to relax when we have to go defensive. In reality, defensive operations subject us to as much risk of injury from collapse as interior operations if we’re not observing good collapse zones. Master streams and aerial streams hitting the building walls with great force can increase the chances of collapse. Therefore, collapse zones should be clearly marked with barricade tape and enforced by division or safety officers during defensive operations.
Position larger-caliber lines, which provide increased water flow and stream reach, in flanking positions and use the strong areas of the building at the corners to minimize the dangers of collapse. Smaller handlines that we rely on in our day-to-day residential work may not be suited for defensive operations where we need to establish a collapse zone. In addition to limited flow, smaller handlines often cause crews operating them to “creep,” or slowly work their way closer and closer to the building, thereby entering the collapse zone, because the reach of the stream doesn’t hit the fire and because firefighters want to be close to the action.
Rather than relying on small handlines, train on getting master streams in service and positioning the aerial device to provide a mobile master stream that can be repositioned when needed. Remember: Aerial devices also need to be out of the collapse zone. Walls can and will fall on ladders, just like they do on firefighters. Keep the aerial above the roofline and back 1½ times the full height of the wall. Positioning the aerial at the corners allows the strong sections of the building to protect the apparatus and the firefighters operating it. Corner positioning also allows the aerial to cover two sides of the building.
A Final Word
Too many firefighters and chief officers have been injured or killed as a result of operating inside the collapse zone. Although the fireground can change rapidly, posing new challenges, collapse should be one of the first factors we consider for any structure fire. Planning for it at the beginning of the incident will help support firefighter safety throughout the incident.
Review Building Construction
Building construction is one of the most important concepts for every firefighter, from the probie to the chief. You can’t cover it too often. Start by reviewing the following questions with your crew.
- What are the five most common types of buildings and what are their potential collapse types?
- What are the three most common types of wall collapse?
Based on a worst-case collapse scenario, what type of wall will extend out the farthest, and how much distance should you set for your collapse zone?
Map Out the Zone
- In your response area, select some buildings that would present dangers during defensive fire operations.
- Classify each building into one of the five most common building types. Review the collapse potential for each building.
- Using traffic cones, have crews set up collapse zones that they believe would provide proper safety.
Deploy some handlines and master stream devices, positioning them for a defensive operation. Discuss the use of flanking positions to limit exposure.
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