The fire resistance floor assembly plays a primary role preventing ___________ accumulation of fire and products of combustion.

• A. Vertical.
• B. Horizontal.
• C. Heavy.
• D. Lateral.

Answer: (A)

The main idea is that a fire-resistance floor-assembly acts as a vertical barrier between levels. Its purpose is to slow or stop fire, heat, and smoke from moving upward into the space above, preventing vertical accumulation of fire and its products through the floor. Horizontal spread, by contrast, is mainly controlled by walls, doors, and openings on the same level, not by the floor assembly. This is why the best choice describes preventing vertical accumulation of fire and combustion products.