Which of the following is a listed collapse type?

• A. Dome
• B. Wedge
• C. A-frame
• D. Lean-to

Answer: (C)

Recognizing listed collapse types means identifying a standard, recognizable pattern of how a building can fail that rescuers train to expect. An A-frame collapse appears when two steeply pitched roof planes fail and the structure drops into a shape that forms an A, with the roof slopes converging toward the center and the walls bowing. This creates the distinctive triangular, “A” profile and indicates specific hazards and tool placement considerations for gaining access safely. It’s a clearly defined pattern used in rescue training because of its predictable geometry and the way it changes where space, venting, and stabilization are needed.

Dome collapse would produce a curved, rounded failure rather than an A-shaped frame; a wedge collapse involves a triangular failure on one side, not the symmetric A-frame pattern; and a lean-to involves a single sloped collapse rather than two slopes meeting at a peak. These differences help explain why the A-frame is the listed collapse type in this context.