In collapse indicators, what does 1.5x height represent?

• A. The safe stand-off distance
• B. The area of ventilation
• C. The collapse zone height multiplier
• D. The floor-to-ceiling height

Answer: (C)

In collapse indicators, the 1.5x height is used to define the collapse zone distance. It’s the height multiplier that tells you how far debris could travel if the structure starts to fail, so you retreat to a safe perimeter about 1.5 times the building’s height away from the exterior. This isn’t about safe stand-off for ventilation, nor the floor-to-ceiling height—it's specifically the distance to stay clear of potential falling debris. For example, a building 10 meters tall would have a collapse zone about 15 meters from the building.