Which design decision primarily controls how heat and flames can transfer between compartments?

• A. The arrangement of interior signage
• B. The type of ceiling tiles
• C. The integrity of compartment boundaries, including fire-rated walls and doors
• D. The selection of occupants

Answer: (C)

Compartmentation and fire barriers are what limit heat and flame spread from one space to another. By using fire-resistance–rated walls, floors, and especially doors, the design creates a robust boundary that slows or stops heat transfer and flame movement for a defined period. When these boundaries are intact and properly sealed and penetrations are firestopped, adjacent compartments stay cooler longer, giving occupants time to evacuate and firefighters time to respond.

The other options don’t address this physical barrier. Interior signage doesn’t affect heat transfer, ceiling tile type isn’t the primary control for between-room flame spread, and the number or arrangement of occupants doesn’t alter the building’s ability to block heat and flames.

So, ensuring the integrity of compartment boundaries, including fire-rated walls and doors, is the main design decision that controls how heat and flames move between compartments.