A ______ tends to have a core of nearly pure fuel and burns from the outer edge towards the middle.

A ______ tends to have a core of nearly pure fuel and burns from the outer edge towards the middle.

• A. Flame front
• B. Fireball
• C. Flashover
• D. Smoke plume

Answer: (B)

A fireball forms when a fuel-rich gas mixture in a confined space ignites, creating a sphere where the center remains largely fuel with limited oxygen. The outer edge hits more air and lights up first, so flames appear around the perimeter. As the fire continues, the outer layer burns inward toward the center as mixing brings enough oxygen to ignite the remaining fuel. This inward-burning pattern from a fuel-rich core is what this description points to. The other options don’t describe a structure with a fuel-heavy core burning from the outside in: a flame front is simply the leading edge of a flame into unburned gas, flashover is a rapid room-wide ignition, and a smoke plume is just hot gases rising without this inward-burning core.

A fireball forms when a fuel-rich gas mixture in a confined space ignites, creating a sphere where the center remains largely fuel with limited oxygen. The outer edge hits more air and lights up first, so flames appear around the perimeter. As the fire continues, the outer layer burns inward toward the center as mixing brings enough oxygen to ignite the remaining fuel. This inward-burning pattern from a fuel-rich core is what this description points to. The other options don’t describe a structure with a fuel-heavy core burning from the outside in: a flame front is simply the leading edge of a flame into unburned gas, flashover is a rapid room-wide ignition, and a smoke plume is just hot gases rising without this inward-burning core.